* [PATCH v9 01/22] arm64: cpufeature: Add cpucap for HPMN0
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 02/22] KVM: arm64: Reorganize PMU includes Colton Lewis
` (22 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
Add a capability for FEAT_HPMN0, whether MDCR_EL2.HPMN can specify 0
counters reserved for the guest.
This required changing HPMN0 to an UnsignedEnum in tools/sysreg
because otherwise not all the appropriate macros are generated to add
it to arm64_cpu_capabilities_arm64_features.
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm64/kernel/cpufeature.c | 10 +++++++++-
arch/arm64/kvm/sys_regs.c | 5 ++++-
arch/arm64/tools/cpucaps | 1 +
arch/arm64/tools/sysreg | 6 +++---
4 files changed, 17 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 32102c3912fa7..f8431cf858619 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -77,7 +77,7 @@
#include <linux/percpu.h>
#include <linux/sched/isolation.h>
-#include <asm/arm_pmuv3.h>
+#include <linux/perf/arm_pmuv3.h>
#include <asm/cpu.h>
#include <asm/cpufeature.h>
#include <asm/cpu_ops.h>
@@ -564,6 +564,7 @@ static const struct arm64_ftr_bits ftr_id_mmfr0[] = {
};
static const struct arm64_ftr_bits ftr_id_aa64dfr0[] = {
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64DFR0_EL1_HPMN0_SHIFT, 4, 0),
S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64DFR0_EL1_DoubleLock_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64DFR0_EL1_PMSVer_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64DFR0_EL1_CTX_CMPs_SHIFT, 4, 0),
@@ -3012,6 +3013,13 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.matches = has_cpuid_feature,
ARM64_CPUID_FIELDS(ID_AA64MMFR0_EL1, FGT, FGT2)
},
+ {
+ .desc = "HPMN0",
+ .type = ARM64_CPUCAP_SYSTEM_FEATURE,
+ .capability = ARM64_HAS_HPMN0,
+ .matches = has_cpuid_feature,
+ ARM64_CPUID_FIELDS(ID_AA64DFR0_EL1, HPMN0, IMP)
+ },
#ifdef CONFIG_ARM64_SME
{
.desc = "Scalable Matrix Extension",
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 44aae52c473d7..f7f750b7a91c4 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -2219,6 +2219,8 @@ static u64 sanitise_id_aa64dfr0_el1(const struct kvm_vcpu *vcpu, u64 val)
if (kvm_vcpu_has_pmu(vcpu))
val |= SYS_FIELD_PREP(ID_AA64DFR0_EL1, PMUVer,
kvm_arm_pmu_get_pmuver_limit());
+ else
+ val &= ~ID_AA64DFR0_EL1_HPMN0_MASK;
/* Hide SPE from guests */
val &= ~ID_AA64DFR0_EL1_PMSVer_MASK;
@@ -3417,7 +3419,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
ID_AA64DFR0_EL1_DoubleLock_MASK |
ID_AA64DFR0_EL1_WRPs_MASK |
ID_AA64DFR0_EL1_PMUVer_MASK |
- ID_AA64DFR0_EL1_DebugVer_MASK),
+ ID_AA64DFR0_EL1_DebugVer_MASK |
+ ID_AA64DFR0_EL1_HPMN0_MASK),
ID_SANITISED(ID_AA64DFR1_EL1),
ID_UNALLOCATED(5,2),
ID_UNALLOCATED(5,3),
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 2775ba3359cfe..a309c18235e71 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -43,6 +43,7 @@ HAS_GIC_PRIO_MASKING
HAS_GIC_PRIO_RELAXED_SYNC
HAS_ICH_HCR_EL2_TDIR
HAS_HCR_NV1
+HAS_HPMN0
HAS_HCX
HAS_LDAPR
HAS_LPA2
diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
index e2d37ee221b84..1035b406ef183 100644
--- a/arch/arm64/tools/sysreg
+++ b/arch/arm64/tools/sysreg
@@ -1679,9 +1679,9 @@ EndEnum
EndSysreg
Sysreg ID_AA64DFR0_EL1 3 0 0 5 0
-Enum 63:60 HPMN0
- 0b0000 UNPREDICTABLE
- 0b0001 DEF
+UnsignedEnum 63:60 HPMN0
+ 0b0000 NI
+ 0b0001 IMP
EndEnum
UnsignedEnum 59:56 ExtTrcBuff
0b0000 NI
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 02/22] KVM: arm64: Reorganize PMU includes
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
2026-09-24 17:29 ` [PATCH v9 01/22] arm64: cpufeature: Add cpucap for HPMN0 Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 03/22] KVM: arm64: Reorganize PMU functions Colton Lewis
` (21 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
From: Marc Zyngier <maz@kernel.org>
Including *all* of asm/kvm_host.h in asm/arm_pmuv3.h is a bad idea
because that is much more than arm_pmuv3.h logically needs and creates
a circular dependency that makes it easy to introduce compiler errors
when editing this code.
asm/kvm_host.h includes kvm/arm_pmu.h includes perf/arm_pmuv3.h
includes asm/arm_pmuv3.h includes asm/kvm_host.h
Reorganize the PMU includes to be more sane. In particular:
- Remove the circular dependency by removing the kvm_host.h include
from asm/arm_pmuv3.h since 99% of it isn't needed.
- Move the remaining tiny bit of KVM/PMU interface from kvm_host.h
into arm_pmu.h
- Conditionally on ARM64, include the more targeted arm_pmu.h directly
in the arm_pmuv3.c driver.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm64/include/asm/arm_pmuv3.h | 2 --
arch/arm64/include/asm/kvm_host.h | 14 --------------
drivers/perf/arm_pmuv3.c | 5 +++++
include/kvm/arm_pmu.h | 19 +++++++++++++++++++
4 files changed, 24 insertions(+), 16 deletions(-)
diff --git a/arch/arm64/include/asm/arm_pmuv3.h b/arch/arm64/include/asm/arm_pmuv3.h
index 8a777dec8d88a..cf2b2212e00a2 100644
--- a/arch/arm64/include/asm/arm_pmuv3.h
+++ b/arch/arm64/include/asm/arm_pmuv3.h
@@ -6,8 +6,6 @@
#ifndef __ASM_PMUV3_H
#define __ASM_PMUV3_H
-#include <asm/kvm_host.h>
-
#include <asm/cpufeature.h>
#include <asm/sysreg.h>
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 27fe0cd5b2d7a..217c36af1ca51 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1467,25 +1467,11 @@ void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu);
void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
-static inline bool kvm_pmu_counter_deferred(struct perf_event_attr *attr)
-{
- return (!has_vhe() && attr->exclude_host);
-}
-
#ifdef CONFIG_KVM
-void kvm_set_pmu_events(u64 set, struct perf_event_attr *attr);
-void kvm_clr_pmu_events(u64 clr);
-bool kvm_set_pmuserenr(u64 val);
void kvm_enable_trbe(void);
void kvm_disable_trbe(void);
void kvm_tracing_set_el1_configuration(u64 trfcr_while_in_guest);
#else
-static inline void kvm_set_pmu_events(u64 set, struct perf_event_attr *attr) {}
-static inline void kvm_clr_pmu_events(u64 clr) {}
-static inline bool kvm_set_pmuserenr(u64 val)
-{
- return false;
-}
static inline void kvm_enable_trbe(void) {}
static inline void kvm_disable_trbe(void) {}
static inline void kvm_tracing_set_el1_configuration(u64 trfcr_while_in_guest) {}
diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
index 03359e078301f..fbd631ec71a65 100644
--- a/drivers/perf/arm_pmuv3.c
+++ b/drivers/perf/arm_pmuv3.c
@@ -10,6 +10,11 @@
#include <asm/cputype.h>
#include <asm/irq_regs.h>
+
+#if defined(CONFIG_ARM64)
+#include <kvm/arm_pmu.h>
+#endif
+
#include <asm/perf_event.h>
#include <asm/virt.h>
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 6b4a118d17ca9..93f41ac77c25f 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -9,12 +9,22 @@
#include <linux/perf_event.h>
#include <linux/perf/arm_pmuv3.h>
+#include <linux/perf/arm_pmu.h>
#define KVM_ARMV8_PMU_MAX_COUNTERS 32
/* PPI #23 - architecturally specified for GICv5 */
#define KVM_ARMV8_PMU_GICV5_IRQ 0x20000017
+#define kvm_pmu_counter_deferred(attr) \
+ ({ \
+ !has_vhe() && (attr)->exclude_host; \
+ })
+
+struct kvm;
+struct kvm_device_attr;
+struct kvm_vcpu;
+
#if IS_ENABLED(CONFIG_HW_PERF_EVENTS) && IS_ENABLED(CONFIG_KVM)
struct kvm_pmc {
u8 idx; /* index into the pmu->pmc array */
@@ -68,6 +78,9 @@ int kvm_arm_pmu_v3_has_attr(struct kvm_vcpu *vcpu,
int kvm_arm_pmu_v3_enable(struct kvm_vcpu *vcpu);
struct kvm_pmu_events *kvm_get_pmu_events(void);
+void kvm_set_pmu_events(u64 set, struct perf_event_attr *attr);
+void kvm_clr_pmu_events(u64 clr);
+bool kvm_set_pmuserenr(u64 val);
void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu);
void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
void kvm_vcpu_pmu_resync_el0(void);
@@ -165,6 +178,12 @@ static inline u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1)
#define kvm_vcpu_has_pmu(vcpu) ({ false; })
#define kvm_vcpu_has_pmuv3_strict(vcpu) ({ false; })
static inline void kvm_pmu_update_vcpu_events(struct kvm_vcpu *vcpu) {}
+static inline void kvm_set_pmu_events(u64 set, struct perf_event_attr *attr) {}
+static inline void kvm_clr_pmu_events(u64 clr) {}
+static inline bool kvm_set_pmuserenr(u64 val)
+{
+ return false;
+}
static inline void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu) {}
static inline void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu) {}
static inline void kvm_vcpu_reload_pmu(struct kvm_vcpu *vcpu) {}
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 03/22] KVM: arm64: Reorganize PMU functions
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
2026-09-24 17:29 ` [PATCH v9 01/22] arm64: cpufeature: Add cpucap for HPMN0 Colton Lewis
2026-09-24 17:29 ` [PATCH v9 02/22] KVM: arm64: Reorganize PMU includes Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 04/22] perf: arm_pmuv3: Generalize counter bitmasks Colton Lewis
` (20 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
A lot of functions in pmu-emul.c aren't specific to the emulated PMU
implementation. Move them to the more appropriate pmu.c file where
shared PMU functions should live.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm64/kvm/pmu-emul.c | 702 +------------------------------------
arch/arm64/kvm/pmu.c | 705 ++++++++++++++++++++++++++++++++++++++
include/kvm/arm_pmu.h | 9 +-
3 files changed, 714 insertions(+), 702 deletions(-)
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 5b1af7e2176fa..2a2c924fc6b8f 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -17,19 +17,10 @@
#define PERF_ATTR_CFG1_COUNTER_64BIT BIT(0)
-static LIST_HEAD(arm_pmus);
-static DEFINE_MUTEX(arm_pmus_lock);
-
static void kvm_pmu_create_perf_event(struct kvm_pmc *pmc);
static void kvm_pmu_release_perf_event(struct kvm_pmc *pmc);
static bool kvm_pmu_counter_is_enabled(struct kvm_pmc *pmc);
-bool kvm_supports_guest_pmuv3(void)
-{
- guard(mutex)(&arm_pmus_lock);
- return !list_empty(&arm_pmus);
-}
-
static struct kvm_vcpu *kvm_pmc_to_vcpu(const struct kvm_pmc *pmc)
{
return container_of(pmc, struct kvm_vcpu, arch.pmu.pmc[pmc->idx]);
@@ -40,46 +31,6 @@ static struct kvm_pmc *kvm_vcpu_idx_to_pmc(struct kvm_vcpu *vcpu, int cnt_idx)
return &vcpu->arch.pmu.pmc[cnt_idx];
}
-static u32 __kvm_pmu_event_mask(unsigned int pmuver)
-{
- switch (pmuver) {
- case ID_AA64DFR0_EL1_PMUVer_IMP:
- return GENMASK(9, 0);
- case ID_AA64DFR0_EL1_PMUVer_V3P1:
- case ID_AA64DFR0_EL1_PMUVer_V3P4:
- case ID_AA64DFR0_EL1_PMUVer_V3P5:
- case ID_AA64DFR0_EL1_PMUVer_V3P7:
- return GENMASK(15, 0);
- default: /* Shouldn't be here, just for sanity */
- WARN_ONCE(1, "Unknown PMU version %d\n", pmuver);
- return 0;
- }
-}
-
-static u32 kvm_pmu_event_mask(struct kvm *kvm)
-{
- u64 dfr0 = kvm_read_vm_id_reg(kvm, SYS_ID_AA64DFR0_EL1);
- u8 pmuver = SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer, dfr0);
-
- return __kvm_pmu_event_mask(pmuver);
-}
-
-u64 kvm_pmu_evtyper_mask(struct kvm *kvm)
-{
- u64 mask = ARMV8_PMU_EXCLUDE_EL1 | ARMV8_PMU_EXCLUDE_EL0 |
- kvm_pmu_event_mask(kvm);
-
- if (kvm_has_feat(kvm, ID_AA64PFR0_EL1, EL2, IMP))
- mask |= ARMV8_PMU_INCLUDE_EL2;
-
- if (kvm_has_feat(kvm, ID_AA64PFR0_EL1, EL3, IMP))
- mask |= ARMV8_PMU_EXCLUDE_NS_EL0 |
- ARMV8_PMU_EXCLUDE_NS_EL1 |
- ARMV8_PMU_EXCLUDE_EL3;
-
- return mask;
-}
-
/**
* kvm_pmc_is_64bit - determine if counter is 64bit
* @pmc: counter context
@@ -272,59 +223,6 @@ void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu)
irq_work_sync(&vcpu->arch.pmu.overflow_work);
}
-static u64 kvm_pmu_hyp_counter_mask(struct kvm_vcpu *vcpu)
-{
- unsigned int hpmn, n;
-
- if (!vcpu_has_nv(vcpu))
- return 0;
-
- hpmn = SYS_FIELD_GET(MDCR_EL2, HPMN, __vcpu_sys_reg(vcpu, MDCR_EL2));
- n = vcpu->kvm->arch.nr_pmu_counters;
-
- /*
- * Programming HPMN to a value greater than PMCR_EL0.N is
- * CONSTRAINED UNPREDICTABLE. Make the implementation choice that an
- * UNKNOWN number of counters (in our case, zero) are reserved for EL2.
- */
- if (hpmn >= n)
- return 0;
-
- /*
- * Programming HPMN=0 is CONSTRAINED UNPREDICTABLE if FEAT_HPMN0 isn't
- * implemented. Since KVM's ability to emulate HPMN=0 does not directly
- * depend on hardware (all PMU registers are trapped), make the
- * implementation choice that all counters are included in the second
- * range reserved for EL2/EL3.
- */
- return GENMASK(n - 1, hpmn);
-}
-
-bool kvm_pmu_counter_is_hyp(struct kvm_vcpu *vcpu, unsigned int idx)
-{
- return kvm_pmu_hyp_counter_mask(vcpu) & BIT(idx);
-}
-
-u64 kvm_pmu_accessible_counter_mask(struct kvm_vcpu *vcpu)
-{
- u64 mask = kvm_pmu_implemented_counter_mask(vcpu);
-
- if (!vcpu_has_nv(vcpu) || vcpu_is_el2(vcpu))
- return mask;
-
- return mask & ~kvm_pmu_hyp_counter_mask(vcpu);
-}
-
-u64 kvm_pmu_implemented_counter_mask(struct kvm_vcpu *vcpu)
-{
- u64 val = FIELD_GET(ARMV8_PMU_PMCR_N, kvm_vcpu_read_pmcr(vcpu));
-
- if (val == 0)
- return BIT(ARMV8_PMU_CYCLE_IDX);
- else
- return GENMASK(val - 1, 0) | BIT(ARMV8_PMU_CYCLE_IDX);
-}
-
static void kvm_pmc_enable_perf_event(struct kvm_pmc *pmc)
{
if (!pmc->perf_event) {
@@ -370,7 +268,7 @@ void kvm_pmu_reprogram_counter_mask(struct kvm_vcpu *vcpu, u64 val)
* counter where the values of the global enable control, PMOVSSET_EL0[n], and
* PMINTENSET_EL1[n] are all 1.
*/
-static bool kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
+bool kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
{
u64 reg = __vcpu_sys_reg(vcpu, PMOVSSET_EL0);
@@ -393,16 +291,6 @@ static bool kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
return reg;
}
-static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
-{
- struct kvm_pmu *pmu = &vcpu->arch.pmu;
-
- if (unlikely(!irqchip_in_kernel(vcpu->kvm)))
- return;
-
- WARN_ON(kvm_vgic_inject_irq(vcpu->kvm, vcpu, pmu->irq_num,
- kvm_pmu_overflow_status(vcpu), pmu));
-}
bool kvm_pmu_should_notify_user(struct kvm_vcpu *vcpu)
{
@@ -423,43 +311,6 @@ bool kvm_pmu_update_run(struct kvm_vcpu *vcpu)
return update;
}
-/**
- * kvm_pmu_flush_hwstate - flush pmu state to cpu
- * @vcpu: The vcpu pointer
- *
- * Check if the PMU has overflowed while we were running in the host, and inject
- * an interrupt if that was the case.
- */
-void kvm_pmu_flush_hwstate(struct kvm_vcpu *vcpu)
-{
- kvm_pmu_update_state(vcpu);
-}
-
-/**
- * kvm_pmu_sync_hwstate - sync pmu state from cpu
- * @vcpu: The vcpu pointer
- *
- * Check if the PMU has overflowed while we were running in the guest, and
- * inject an interrupt if that was the case.
- */
-void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu)
-{
- kvm_pmu_update_state(vcpu);
-}
-
-/*
- * When perf interrupt is an NMI, we cannot safely notify the vcpu corresponding
- * to the event.
- * This is why we need a callback to do it once outside of the NMI context.
- */
-static void kvm_pmu_perf_overflow_notify_vcpu(struct irq_work *work)
-{
- struct kvm_vcpu *vcpu;
-
- vcpu = container_of(work, struct kvm_vcpu, arch.pmu.overflow_work);
- kvm_vcpu_kick(vcpu);
-}
-
/*
* Perform an increment on any of the counters described in @mask,
* generating the overflow if required, and propagate it as a chained
@@ -771,133 +622,6 @@ void kvm_pmu_set_counter_event_type(struct kvm_vcpu *vcpu, u64 data,
kvm_pmu_create_perf_event(pmc);
}
-void kvm_host_pmu_init(struct arm_pmu *pmu)
-{
- struct arm_pmu_entry *entry;
-
- /*
- * Check the sanitised PMU version for the system, as KVM does not
- * support implementations where PMUv3 exists on a subset of CPUs.
- */
- if (!pmuv3_implemented(kvm_arm_pmu_get_pmuver_limit()))
- return;
-
- guard(mutex)(&arm_pmus_lock);
-
- entry = kmalloc_obj(*entry);
- if (!entry)
- return;
-
- entry->arm_pmu = pmu;
- list_add_tail(&entry->entry, &arm_pmus);
-}
-
-static struct arm_pmu *kvm_pmu_probe_armpmu(void)
-{
- struct arm_pmu_entry *entry;
- struct arm_pmu *pmu;
- int cpu;
-
- guard(mutex)(&arm_pmus_lock);
-
- /*
- * It is safe to use a stale cpu to iterate the list of PMUs so long as
- * the same value is used for the entirety of the loop. Given this, and
- * the fact that no percpu data is used for the lookup there is no need
- * to disable preemption.
- *
- * It is still necessary to get a valid cpu, though, to probe for the
- * default PMU instance as userspace is not required to specify a PMU
- * type. In order to uphold the preexisting behavior KVM selects the
- * PMU instance for the core during vcpu init. A dependent use
- * case would be a user with disdain of all things big.LITTLE that
- * affines the VMM to a particular cluster of cores.
- *
- * In any case, userspace should just do the sane thing and use the UAPI
- * to select a PMU type directly. But, be wary of the baggage being
- * carried here.
- */
- cpu = raw_smp_processor_id();
- list_for_each_entry(entry, &arm_pmus, entry) {
- pmu = entry->arm_pmu;
-
- if (cpumask_test_cpu(cpu, &pmu->supported_cpus))
- return pmu;
- }
-
- return NULL;
-}
-
-static u64 __compute_pmceid(struct arm_pmu *pmu, bool pmceid1)
-{
- u32 hi[2], lo[2];
-
- bitmap_to_arr32(lo, pmu->pmceid_bitmap, ARMV8_PMUV3_MAX_COMMON_EVENTS);
- bitmap_to_arr32(hi, pmu->pmceid_ext_bitmap, ARMV8_PMUV3_MAX_COMMON_EVENTS);
-
- return ((u64)hi[pmceid1] << 32) | lo[pmceid1];
-}
-
-static u64 compute_pmceid0(struct kvm_vcpu *vcpu)
-{
- u64 val = __compute_pmceid(vcpu->kvm->arch.arm_pmu, 0);
-
- /* always support SW_INCR */
- val |= BIT(ARMV8_PMUV3_PERFCTR_SW_INCR);
- /* always support CHAIN */
- val |= BIT(ARMV8_PMUV3_PERFCTR_CHAIN);
- return val;
-}
-
-static u64 compute_pmceid1(struct kvm_vcpu *vcpu)
-{
- u64 val = __compute_pmceid(vcpu->kvm->arch.arm_pmu, 1);
-
- /*
- * If KVM_ARM_VCPU_PMU_V3_STRICT is not set, PMMIR_EL1 is
- * unconditionally RAZ, so don't advertise STALL_SLOT* events.
- */
- if (!kvm_vcpu_has_pmuv3_strict(vcpu))
- val &= ~(BIT_ULL(ARMV8_PMUV3_PERFCTR_STALL_SLOT - 32) |
- BIT_ULL(ARMV8_PMUV3_PERFCTR_STALL_SLOT_FRONTEND - 32) |
- BIT_ULL(ARMV8_PMUV3_PERFCTR_STALL_SLOT_BACKEND - 32));
-
- return val;
-}
-
-u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1)
-{
- unsigned long *bmap = vcpu->kvm->arch.pmu_filter;
- u64 val, mask = 0;
- int base, i, nr_events;
-
- if (!pmceid1) {
- val = compute_pmceid0(vcpu);
- base = 0;
- } else {
- val = compute_pmceid1(vcpu);
- base = 32;
- }
-
- if (!bmap)
- return val;
-
- nr_events = kvm_pmu_event_mask(vcpu->kvm) + 1;
-
- for (i = 0; i < 32; i += 8) {
- u64 byte;
-
- byte = bitmap_get_value8(bmap, base + i);
- mask |= byte << i;
- if (nr_events >= (0x4000 + base + 32)) {
- byte = bitmap_get_value8(bmap, 0x4000 + base + i);
- mask |= byte << (32 + i);
- }
- }
-
- return val & mask;
-}
-
void kvm_vcpu_reload_pmu(struct kvm_vcpu *vcpu)
{
u64 mask = kvm_pmu_implemented_counter_mask(vcpu);
@@ -909,430 +633,6 @@ void kvm_vcpu_reload_pmu(struct kvm_vcpu *vcpu)
kvm_pmu_reprogram_counter_mask(vcpu, mask);
}
-int kvm_arm_pmu_v3_enable(struct kvm_vcpu *vcpu)
-{
- if (!vcpu->arch.pmu.created)
- return -EINVAL;
-
- /*
- * A valid interrupt configuration for the PMU is either to have a
- * properly configured interrupt number and using an in-kernel
- * irqchip, or to not have an in-kernel GIC and not set an IRQ.
- */
- if (irqchip_in_kernel(vcpu->kvm)) {
- int irq = vcpu->arch.pmu.irq_num;
- /*
- * If we are using an in-kernel vgic, at this point we know
- * the vgic will be initialized, so we can check the PMU irq
- * number against the dimensions of the vgic and make sure
- * it's valid.
- */
- if (!irq_is_ppi(vcpu->kvm, irq) &&
- !vgic_valid_spi(vcpu->kvm, irq))
- return -EINVAL;
- } else if (kvm_arm_pmu_irq_initialized(vcpu)) {
- return -EINVAL;
- }
-
- return 0;
-}
-
-static int kvm_arm_pmu_v3_init(struct kvm_vcpu *vcpu)
-{
- /* Only possible when using KVM_ARM_VCPU_PMU_V3_STRICT */
- if (!vcpu->kvm->arch.arm_pmu)
- return -ENXIO;
-
- if (irqchip_in_kernel(vcpu->kvm)) {
- int ret;
-
- /*
- * If using the PMU with an in-kernel virtual GIC
- * implementation, we require the GIC to be already
- * initialized when initializing the PMU.
- */
- if (!vgic_initialized(vcpu->kvm))
- return -ENODEV;
-
- if (!kvm_arm_pmu_irq_initialized(vcpu)) {
- if (!vgic_is_v5(vcpu->kvm))
- return -ENXIO;
-
- /* Use the architected irq number for GICv5. */
- vcpu->arch.pmu.irq_num = KVM_ARMV8_PMU_GICV5_IRQ;
- }
-
- ret = kvm_vgic_set_owner(vcpu, vcpu->arch.pmu.irq_num,
- &vcpu->arch.pmu);
- if (ret)
- return ret;
- }
-
- init_irq_work(&vcpu->arch.pmu.overflow_work,
- kvm_pmu_perf_overflow_notify_vcpu);
-
- vcpu->arch.pmu.created = true;
- return 0;
-}
-
-/*
- * For one VM the interrupt type must be same for each vcpu.
- * As a PPI, the interrupt number is the same for all vcpus,
- * while as an SPI it must be a separate number per vcpu.
- */
-static bool pmu_irq_is_valid(struct kvm *kvm, int irq)
-{
- unsigned long i;
- struct kvm_vcpu *vcpu;
-
- /* On GICv5, the PMUIRQ is architecturally mandated to be PPI 23 */
- if (vgic_is_v5(kvm) && irq != KVM_ARMV8_PMU_GICV5_IRQ)
- return false;
-
- kvm_for_each_vcpu(i, vcpu, kvm) {
- if (!kvm_arm_pmu_irq_initialized(vcpu))
- continue;
-
- if (irq_is_ppi(vcpu->kvm, irq)) {
- if (vcpu->arch.pmu.irq_num != irq)
- return false;
- } else {
- if (vcpu->arch.pmu.irq_num == irq)
- return false;
- }
- }
-
- return true;
-}
-
-/**
- * kvm_arm_pmu_get_max_counters - Return the max number of PMU counters.
- * @kvm: The kvm pointer
- */
-u8 kvm_arm_pmu_get_max_counters(struct kvm *kvm)
-{
- struct arm_pmu *arm_pmu = kvm->arch.arm_pmu;
-
- /*
- * Under KVM_ARM_VCPU_PMU_V3_STRICT no PMU exists until userspace sets
- * one, so this can be reached before arm_pmu is set. Report no
- * counters in that case.
- */
- if (!arm_pmu)
- return 0;
-
- /*
- * PMUv3 requires that all event counters are capable of counting any
- * event, though the same may not be true of non-PMUv3 hardware.
- */
- if (cpus_have_final_cap(ARM64_WORKAROUND_PMUV3_IMPDEF_TRAPS))
- return 1;
-
- /*
- * The arm_pmu->cntr_mask considers the fixed counter(s) as well.
- * Ignore those and return only the general-purpose counters.
- */
- return bitmap_weight(arm_pmu->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS);
-}
-
-static void kvm_arm_set_nr_counters(struct kvm *kvm, unsigned int nr)
-{
- kvm->arch.nr_pmu_counters = nr;
-
- /* Reset MDCR_EL2.HPMN behind the vcpus' back... */
- if (test_bit(KVM_ARM_VCPU_HAS_EL2, kvm->arch.vcpu_features)) {
- struct kvm_vcpu *vcpu;
- unsigned long i;
-
- kvm_for_each_vcpu(i, vcpu, kvm) {
- u64 val = __vcpu_sys_reg(vcpu, MDCR_EL2);
- val &= ~MDCR_EL2_HPMN;
- val |= FIELD_PREP(MDCR_EL2_HPMN, kvm->arch.nr_pmu_counters);
- __vcpu_assign_sys_reg(vcpu, MDCR_EL2, val);
- }
- }
-}
-
-static void kvm_arm_set_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu)
-{
- lockdep_assert_held(&kvm->arch.config_lock);
-
- kvm->arch.arm_pmu = arm_pmu;
- kvm_arm_set_nr_counters(kvm, kvm_arm_pmu_get_max_counters(kvm));
-}
-
-/**
- * kvm_arm_set_default_pmu - No PMU set and KVM_ARM_VCPU_PMU_V3_STRICT not
- * set, get the default one.
- * @kvm: The kvm pointer
- *
- * The observant among you will notice that the supported_cpus
- * mask does not get updated for the default PMU even though it
- * is quite possible the selected instance supports only a
- * subset of cores in the system. This is intentional, and
- * upholds the preexisting behavior on heterogeneous systems
- * where vCPUs can be scheduled on any core but the guest
- * counters could stop working.
- */
-int kvm_arm_set_default_pmu(struct kvm *kvm)
-{
- struct arm_pmu *arm_pmu = kvm_pmu_probe_armpmu();
-
- if (!arm_pmu)
- return -ENODEV;
-
- kvm_arm_set_pmu(kvm, arm_pmu);
- return 0;
-}
-
-static int kvm_arm_pmu_v3_set_pmu(struct kvm_vcpu *vcpu, int pmu_id)
-{
- struct kvm *kvm = vcpu->kvm;
- struct arm_pmu_entry *entry;
- struct arm_pmu *arm_pmu;
- int ret = -ENXIO;
-
- lockdep_assert_held(&kvm->arch.config_lock);
- mutex_lock(&arm_pmus_lock);
-
- list_for_each_entry(entry, &arm_pmus, entry) {
- arm_pmu = entry->arm_pmu;
- if (arm_pmu->pmu.type == pmu_id) {
- if (kvm_vm_has_ran_once(kvm) ||
- (kvm->arch.pmu_filter && kvm->arch.arm_pmu != arm_pmu)) {
- ret = -EBUSY;
- break;
- }
-
- kvm_arm_set_pmu(kvm, arm_pmu);
- cpumask_copy(kvm->arch.supported_cpus, &arm_pmu->supported_cpus);
-
- /*
- * Since a specific PMU is explicitly selected,
- * PMMIR_EL1.SLOTS is deterministic to the guest.
- * If KVM_ARM_VCPU_PMU_V3_STRICT is set, snapshot
- * the value to allow the guest to read it.
- */
- if (kvm_vcpu_has_pmuv3_strict(vcpu))
- kvm->arch.pmmir_slots =
- FIELD_GET(ARMV8_PMU_SLOTS,
- arm_pmu->reg_pmmir);
- ret = 0;
- break;
- }
- }
-
- mutex_unlock(&arm_pmus_lock);
- return ret;
-}
-
-static int kvm_arm_pmu_v3_set_nr_counters(struct kvm_vcpu *vcpu, unsigned int n)
-{
- struct kvm *kvm = vcpu->kvm;
-
- if (!kvm->arch.arm_pmu)
- return -EINVAL;
-
- if (n > kvm_arm_pmu_get_max_counters(kvm))
- return -EINVAL;
-
- kvm_arm_set_nr_counters(kvm, n);
- return 0;
-}
-
-int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
-{
- struct kvm *kvm = vcpu->kvm;
-
- lockdep_assert_held(&kvm->arch.config_lock);
-
- if (!kvm_vcpu_has_pmu(vcpu))
- return -ENODEV;
-
- if (vcpu->arch.pmu.created)
- return -EBUSY;
-
- switch (attr->attr) {
- case KVM_ARM_VCPU_PMU_V3_IRQ: {
- int __user *uaddr = (int __user *)(long)attr->addr;
- int irq;
-
- if (!irqchip_in_kernel(kvm))
- return -EINVAL;
-
- if (get_user(irq, uaddr))
- return -EFAULT;
-
- /* The PMU overflow interrupt can be a PPI or a valid SPI. */
- if (!(irq_is_ppi(vcpu->kvm, irq) || irq_is_spi(vcpu->kvm, irq)))
- return -EINVAL;
-
- if (!pmu_irq_is_valid(kvm, irq))
- return -EINVAL;
-
- if (kvm_arm_pmu_irq_initialized(vcpu))
- return -EBUSY;
-
- kvm_debug("Set kvm ARM PMU irq: %d\n", irq);
- vcpu->arch.pmu.irq_num = irq;
- return 0;
- }
- case KVM_ARM_VCPU_PMU_V3_FILTER: {
- u8 pmuver = kvm_arm_pmu_get_pmuver_limit();
- struct kvm_pmu_event_filter __user *uaddr;
- struct kvm_pmu_event_filter filter;
- int nr_events;
-
- /*
- * Allow userspace to specify an event filter for the entire
- * event range supported by PMUVer of the hardware, rather
- * than the guest's PMUVer for KVM backward compatibility.
- */
- nr_events = __kvm_pmu_event_mask(pmuver) + 1;
-
- uaddr = (struct kvm_pmu_event_filter __user *)(long)attr->addr;
-
- if (copy_from_user(&filter, uaddr, sizeof(filter)))
- return -EFAULT;
-
- if (((u32)filter.base_event + filter.nevents) > nr_events ||
- (filter.action != KVM_PMU_EVENT_ALLOW &&
- filter.action != KVM_PMU_EVENT_DENY))
- return -EINVAL;
-
- if (kvm_vm_has_ran_once(kvm))
- return -EBUSY;
-
- if (!kvm->arch.arm_pmu)
- return -ENXIO;
-
- if (!kvm->arch.pmu_filter) {
- kvm->arch.pmu_filter = bitmap_alloc(nr_events, GFP_KERNEL_ACCOUNT);
- if (!kvm->arch.pmu_filter)
- return -ENOMEM;
-
- /*
- * The default depends on the first applied filter.
- * If it allows events, the default is to deny.
- * Conversely, if the first filter denies a set of
- * events, the default is to allow.
- */
- if (filter.action == KVM_PMU_EVENT_ALLOW)
- bitmap_zero(kvm->arch.pmu_filter, nr_events);
- else
- bitmap_fill(kvm->arch.pmu_filter, nr_events);
- }
-
- if (filter.action == KVM_PMU_EVENT_ALLOW)
- bitmap_set(kvm->arch.pmu_filter, filter.base_event, filter.nevents);
- else
- bitmap_clear(kvm->arch.pmu_filter, filter.base_event, filter.nevents);
-
- return 0;
- }
- case KVM_ARM_VCPU_PMU_V3_SET_PMU: {
- int __user *uaddr = (int __user *)(long)attr->addr;
- int pmu_id;
-
- if (get_user(pmu_id, uaddr))
- return -EFAULT;
-
- return kvm_arm_pmu_v3_set_pmu(vcpu, pmu_id);
- }
- case KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS: {
- unsigned int __user *uaddr = (unsigned int __user *)(long)attr->addr;
- unsigned int n;
-
- if (get_user(n, uaddr))
- return -EFAULT;
-
- return kvm_arm_pmu_v3_set_nr_counters(vcpu, n);
- }
- case KVM_ARM_VCPU_PMU_V3_INIT:
- return kvm_arm_pmu_v3_init(vcpu);
- }
-
- return -ENXIO;
-}
-
-int kvm_arm_pmu_v3_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
-{
- switch (attr->attr) {
- case KVM_ARM_VCPU_PMU_V3_IRQ: {
- int __user *uaddr = (int __user *)(long)attr->addr;
- int irq;
-
- if (!irqchip_in_kernel(vcpu->kvm))
- return -EINVAL;
-
- if (!kvm_vcpu_has_pmu(vcpu))
- return -ENODEV;
-
- if (!kvm_arm_pmu_irq_initialized(vcpu))
- return -ENXIO;
-
- irq = vcpu->arch.pmu.irq_num;
- return put_user(irq, uaddr);
- }
- }
-
- return -ENXIO;
-}
-
-int kvm_arm_pmu_v3_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
-{
- switch (attr->attr) {
- case KVM_ARM_VCPU_PMU_V3_IRQ:
- case KVM_ARM_VCPU_PMU_V3_INIT:
- case KVM_ARM_VCPU_PMU_V3_FILTER:
- case KVM_ARM_VCPU_PMU_V3_SET_PMU:
- case KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS:
- if (kvm_vcpu_has_pmu(vcpu))
- return 0;
- }
-
- return -ENXIO;
-}
-
-u8 kvm_arm_pmu_get_pmuver_limit(void)
-{
- unsigned int pmuver;
-
- pmuver = SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer,
- read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1));
-
- /*
- * Spoof a barebones PMUv3 implementation if the system supports IMPDEF
- * traps of the PMUv3 sysregs
- */
- if (cpus_have_final_cap(ARM64_WORKAROUND_PMUV3_IMPDEF_TRAPS))
- return ID_AA64DFR0_EL1_PMUVer_IMP;
-
- /*
- * Otherwise, treat IMPLEMENTATION DEFINED functionality as
- * unimplemented
- */
- if (pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF)
- return 0;
-
- return min(pmuver, ID_AA64DFR0_EL1_PMUVer_V3P5);
-}
-
-/**
- * kvm_vcpu_read_pmcr - Read PMCR_EL0 register for the vCPU
- * @vcpu: The vcpu pointer
- */
-u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu)
-{
- u64 pmcr = __vcpu_sys_reg(vcpu, PMCR_EL0);
- u64 n = vcpu->kvm->arch.nr_pmu_counters;
-
- if (vcpu_has_nv(vcpu) && !vcpu_is_el2(vcpu))
- n = FIELD_GET(MDCR_EL2_HPMN, __vcpu_sys_reg(vcpu, MDCR_EL2));
-
- return u64_replace_bits(pmcr, n, ARMV8_PMU_PMCR_N);
-}
-
void kvm_pmu_nested_transition(struct kvm_vcpu *vcpu)
{
bool reprogrammed = false;
diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c
index 6b48a3d16d0d5..6f60f86fad387 100644
--- a/arch/arm64/kvm/pmu.c
+++ b/arch/arm64/kvm/pmu.c
@@ -8,8 +8,21 @@
#include <linux/perf/arm_pmu.h>
#include <linux/perf/arm_pmuv3.h>
+#include <kvm/arm_pmu.h>
+#include <kvm/arm_vgic.h>
+
+#include <asm/kvm_emulate.h>
+
+static LIST_HEAD(arm_pmus);
+static DEFINE_MUTEX(arm_pmus_lock);
static DEFINE_PER_CPU(struct kvm_pmu_events, kvm_pmu_events);
+bool kvm_supports_guest_pmuv3(void)
+{
+ guard(mutex)(&arm_pmus_lock);
+ return !list_empty(&arm_pmus);
+}
+
/*
* Given the perf event attributes and system type, determine
* if we are going to need to switch counters at guest entry/exit.
@@ -209,3 +222,695 @@ void kvm_vcpu_pmu_resync_el0(void)
kvm_make_request(KVM_REQ_RESYNC_PMU_EL0, vcpu);
}
+
+void kvm_host_pmu_init(struct arm_pmu *pmu)
+{
+ struct arm_pmu_entry *entry;
+
+ /*
+ * Check the sanitised PMU version for the system, as KVM does not
+ * support implementations where PMUv3 exists on a subset of CPUs.
+ */
+ if (!pmuv3_implemented(kvm_arm_pmu_get_pmuver_limit()))
+ return;
+
+ guard(mutex)(&arm_pmus_lock);
+
+ entry = kmalloc_obj(*entry);
+ if (!entry)
+ return;
+
+ entry->arm_pmu = pmu;
+ list_add_tail(&entry->entry, &arm_pmus);
+}
+
+static struct arm_pmu *kvm_pmu_probe_armpmu(void)
+{
+ struct arm_pmu_entry *entry;
+ struct arm_pmu *pmu;
+ int cpu;
+
+ guard(mutex)(&arm_pmus_lock);
+
+ /*
+ * It is safe to use a stale cpu to iterate the list of PMUs so long as
+ * the same value is used for the entirety of the loop. Given this, and
+ * the fact that no percpu data is used for the lookup there is no need
+ * to disable preemption.
+ *
+ * It is still necessary to get a valid cpu, though, to probe for the
+ * default PMU instance as userspace is not required to specify a PMU
+ * type. In order to uphold the preexisting behavior KVM selects the
+ * PMU instance for the core during vcpu init. A dependent use
+ * case would be a user with disdain of all things big.LITTLE that
+ * affines the VMM to a particular cluster of cores.
+ *
+ * In any case, userspace should just do the sane thing and use the UAPI
+ * to select a PMU type directly. But, be wary of the baggage being
+ * carried here.
+ */
+ cpu = raw_smp_processor_id();
+ list_for_each_entry(entry, &arm_pmus, entry) {
+ pmu = entry->arm_pmu;
+
+ if (cpumask_test_cpu(cpu, &pmu->supported_cpus))
+ return pmu;
+ }
+
+ return NULL;
+}
+
+static u64 __compute_pmceid(struct arm_pmu *pmu, bool pmceid1)
+{
+ u32 hi[2], lo[2];
+
+ bitmap_to_arr32(lo, pmu->pmceid_bitmap, ARMV8_PMUV3_MAX_COMMON_EVENTS);
+ bitmap_to_arr32(hi, pmu->pmceid_ext_bitmap, ARMV8_PMUV3_MAX_COMMON_EVENTS);
+
+ return ((u64)hi[pmceid1] << 32) | lo[pmceid1];
+}
+
+static u64 compute_pmceid0(struct kvm_vcpu *vcpu)
+{
+ u64 val = __compute_pmceid(vcpu->kvm->arch.arm_pmu, 0);
+
+ /* always support SW_INCR */
+ val |= BIT(ARMV8_PMUV3_PERFCTR_SW_INCR);
+ /* always support CHAIN */
+ val |= BIT(ARMV8_PMUV3_PERFCTR_CHAIN);
+ return val;
+}
+
+static u64 compute_pmceid1(struct kvm_vcpu *vcpu)
+{
+ u64 val = __compute_pmceid(vcpu->kvm->arch.arm_pmu, 1);
+
+ /*
+ * If KVM_ARM_VCPU_PMU_V3_STRICT is not set, PMMIR_EL1 is
+ * unconditionally RAZ, so don't advertise STALL_SLOT* events.
+ */
+ if (!kvm_vcpu_has_pmuv3_strict(vcpu))
+ val &= ~(BIT_ULL(ARMV8_PMUV3_PERFCTR_STALL_SLOT - 32) |
+ BIT_ULL(ARMV8_PMUV3_PERFCTR_STALL_SLOT_FRONTEND - 32) |
+ BIT_ULL(ARMV8_PMUV3_PERFCTR_STALL_SLOT_BACKEND - 32));
+
+ return val;
+}
+
+u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1)
+{
+ unsigned long *bmap = vcpu->kvm->arch.pmu_filter;
+ u64 val, mask = 0;
+ int base, i, nr_events;
+
+ if (!pmceid1) {
+ val = compute_pmceid0(vcpu);
+ base = 0;
+ } else {
+ val = compute_pmceid1(vcpu);
+ base = 32;
+ }
+
+ if (!bmap)
+ return val;
+
+ nr_events = kvm_pmu_event_mask(vcpu->kvm) + 1;
+
+ for (i = 0; i < 32; i += 8) {
+ u64 byte;
+
+ byte = bitmap_get_value8(bmap, base + i);
+ mask |= byte << i;
+ if (nr_events >= (0x4000 + base + 32)) {
+ byte = bitmap_get_value8(bmap, 0x4000 + base + i);
+ mask |= byte << (32 + i);
+ }
+ }
+
+ return val & mask;
+}
+
+/*
+ * When perf interrupt is an NMI, we cannot safely notify the vcpu corresponding
+ * to the event.
+ * This is why we need a callback to do it once outside of the NMI context.
+ */
+static void kvm_pmu_perf_overflow_notify_vcpu(struct irq_work *work)
+{
+ struct kvm_vcpu *vcpu;
+
+ vcpu = container_of(work, struct kvm_vcpu, arch.pmu.overflow_work);
+ kvm_vcpu_kick(vcpu);
+}
+
+static u32 __kvm_pmu_event_mask(unsigned int pmuver)
+{
+ switch (pmuver) {
+ case ID_AA64DFR0_EL1_PMUVer_IMP:
+ return GENMASK(9, 0);
+ case ID_AA64DFR0_EL1_PMUVer_V3P1:
+ case ID_AA64DFR0_EL1_PMUVer_V3P4:
+ case ID_AA64DFR0_EL1_PMUVer_V3P5:
+ case ID_AA64DFR0_EL1_PMUVer_V3P7:
+ return GENMASK(15, 0);
+ default: /* Shouldn't be here, just for sanity */
+ WARN_ONCE(1, "Unknown PMU version %d\n", pmuver);
+ return 0;
+ }
+}
+
+u32 kvm_pmu_event_mask(struct kvm *kvm)
+{
+ u64 dfr0 = kvm_read_vm_id_reg(kvm, SYS_ID_AA64DFR0_EL1);
+ u8 pmuver = SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer, dfr0);
+
+ return __kvm_pmu_event_mask(pmuver);
+}
+
+u64 kvm_pmu_evtyper_mask(struct kvm *kvm)
+{
+ u64 mask = ARMV8_PMU_EXCLUDE_EL1 | ARMV8_PMU_EXCLUDE_EL0 |
+ kvm_pmu_event_mask(kvm);
+
+ if (kvm_has_feat(kvm, ID_AA64PFR0_EL1, EL2, IMP))
+ mask |= ARMV8_PMU_INCLUDE_EL2;
+
+ if (kvm_has_feat(kvm, ID_AA64PFR0_EL1, EL3, IMP))
+ mask |= ARMV8_PMU_EXCLUDE_NS_EL0 |
+ ARMV8_PMU_EXCLUDE_NS_EL1 |
+ ARMV8_PMU_EXCLUDE_EL3;
+
+ return mask;
+}
+
+static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
+{
+ struct kvm_pmu *pmu = &vcpu->arch.pmu;
+
+ if (unlikely(!irqchip_in_kernel(vcpu->kvm)))
+ return;
+
+ WARN_ON(kvm_vgic_inject_irq(vcpu->kvm, vcpu, pmu->irq_num,
+ kvm_pmu_overflow_status(vcpu), pmu));
+}
+
+/**
+ * kvm_pmu_flush_hwstate - flush pmu state to cpu
+ * @vcpu: The vcpu pointer
+ *
+ * Check if the PMU has overflowed while we were running in the host, and inject
+ * an interrupt if that was the case.
+ */
+void kvm_pmu_flush_hwstate(struct kvm_vcpu *vcpu)
+{
+ kvm_pmu_update_state(vcpu);
+}
+
+/**
+ * kvm_pmu_sync_hwstate - sync pmu state from cpu
+ * @vcpu: The vcpu pointer
+ *
+ * Check if the PMU has overflowed while we were running in the guest, and
+ * inject an interrupt if that was the case.
+ */
+void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu)
+{
+ kvm_pmu_update_state(vcpu);
+}
+
+int kvm_arm_pmu_v3_enable(struct kvm_vcpu *vcpu)
+{
+ if (!vcpu->arch.pmu.created)
+ return -EINVAL;
+
+ /*
+ * A valid interrupt configuration for the PMU is either to have a
+ * properly configured interrupt number and using an in-kernel
+ * irqchip, or to not have an in-kernel GIC and not set an IRQ.
+ */
+ if (irqchip_in_kernel(vcpu->kvm)) {
+ int irq = vcpu->arch.pmu.irq_num;
+ /*
+ * If we are using an in-kernel vgic, at this point we know
+ * the vgic will be initialized, so we can check the PMU irq
+ * number against the dimensions of the vgic and make sure
+ * it's valid.
+ */
+ if (!irq_is_ppi(vcpu->kvm, irq) && !vgic_valid_spi(vcpu->kvm, irq))
+ return -EINVAL;
+ } else if (kvm_arm_pmu_irq_initialized(vcpu)) {
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int kvm_arm_pmu_v3_init(struct kvm_vcpu *vcpu)
+{
+ /* Only possible when using KVM_ARM_VCPU_PMU_V3_STRICT */
+ if (!vcpu->kvm->arch.arm_pmu)
+ return -ENXIO;
+
+ if (irqchip_in_kernel(vcpu->kvm)) {
+ int ret;
+
+ /*
+ * If using the PMU with an in-kernel virtual GIC
+ * implementation, we require the GIC to be already
+ * initialized when initializing the PMU.
+ */
+ if (!vgic_initialized(vcpu->kvm))
+ return -ENODEV;
+
+ if (!kvm_arm_pmu_irq_initialized(vcpu)) {
+ if (!vgic_is_v5(vcpu->kvm))
+ return -ENXIO;
+
+ /* Use the architected irq number for GICv5. */
+ vcpu->arch.pmu.irq_num = KVM_ARMV8_PMU_GICV5_IRQ;
+ }
+
+ ret = kvm_vgic_set_owner(vcpu, vcpu->arch.pmu.irq_num,
+ &vcpu->arch.pmu);
+ if (ret)
+ return ret;
+ }
+
+ init_irq_work(&vcpu->arch.pmu.overflow_work,
+ kvm_pmu_perf_overflow_notify_vcpu);
+
+ vcpu->arch.pmu.created = true;
+ return 0;
+}
+
+/*
+ * For one VM the interrupt type must be same for each vcpu.
+ * As a PPI, the interrupt number is the same for all vcpus,
+ * while as an SPI it must be a separate number per vcpu.
+ */
+static bool pmu_irq_is_valid(struct kvm *kvm, int irq)
+{
+ unsigned long i;
+ struct kvm_vcpu *vcpu;
+
+ /* On GICv5, the PMUIRQ is architecturally mandated to be PPI 23 */
+ if (vgic_is_v5(kvm) && irq != KVM_ARMV8_PMU_GICV5_IRQ)
+ return false;
+
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ if (!kvm_arm_pmu_irq_initialized(vcpu))
+ continue;
+
+ if (irq_is_ppi(kvm, irq)) {
+ if (vcpu->arch.pmu.irq_num != irq)
+ return false;
+ } else {
+ if (vcpu->arch.pmu.irq_num == irq)
+ return false;
+ }
+ }
+
+ return true;
+}
+
+/**
+ * kvm_arm_pmu_get_max_counters - Return the max number of PMU counters.
+ * @kvm: The kvm pointer
+ */
+u8 kvm_arm_pmu_get_max_counters(struct kvm *kvm)
+{
+ struct arm_pmu *arm_pmu = kvm->arch.arm_pmu;
+
+ /*
+ * Under KVM_ARM_VCPU_PMU_V3_STRICT no PMU exists until userspace sets
+ * one, so this can be reached before arm_pmu is set. Report no
+ * counters in that case.
+ */
+ if (!arm_pmu)
+ return 0;
+
+ /*
+ * PMUv3 requires that all event counters are capable of counting any
+ * event, though the same may not be true of non-PMUv3 hardware.
+ */
+ if (cpus_have_final_cap(ARM64_WORKAROUND_PMUV3_IMPDEF_TRAPS))
+ return 1;
+
+ /*
+ * The arm_pmu->cntr_mask considers the fixed counter(s) as well.
+ * Ignore those and return only the general-purpose counters.
+ */
+ return bitmap_weight(arm_pmu->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS);
+}
+
+static void kvm_arm_set_nr_counters(struct kvm *kvm, unsigned int nr)
+{
+ kvm->arch.nr_pmu_counters = nr;
+
+ /* Reset MDCR_EL2.HPMN behind the vcpus' back... */
+ if (test_bit(KVM_ARM_VCPU_HAS_EL2, kvm->arch.vcpu_features)) {
+ struct kvm_vcpu *vcpu;
+ unsigned long i;
+
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ u64 val = __vcpu_sys_reg(vcpu, MDCR_EL2);
+
+ val &= ~MDCR_EL2_HPMN;
+ val |= FIELD_PREP(MDCR_EL2_HPMN, kvm->arch.nr_pmu_counters);
+ __vcpu_assign_sys_reg(vcpu, MDCR_EL2, val);
+ }
+ }
+}
+
+static void kvm_arm_set_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu)
+{
+ lockdep_assert_held(&kvm->arch.config_lock);
+
+ kvm->arch.arm_pmu = arm_pmu;
+ kvm_arm_set_nr_counters(kvm, kvm_arm_pmu_get_max_counters(kvm));
+}
+
+/**
+ * kvm_arm_set_default_pmu - No PMU set and KVM_ARM_VCPU_PMU_V3_STRICT not
+ * set, get the default one.
+ * @kvm: The kvm pointer
+ *
+ * The observant among you will notice that the supported_cpus
+ * mask does not get updated for the default PMU even though it
+ * is quite possible the selected instance supports only a
+ * subset of cores in the system. This is intentional, and
+ * upholds the preexisting behavior on heterogeneous systems
+ * where vCPUs can be scheduled on any core but the guest
+ * counters could stop working.
+ */
+int kvm_arm_set_default_pmu(struct kvm *kvm)
+{
+ struct arm_pmu *arm_pmu = kvm_pmu_probe_armpmu();
+
+ if (!arm_pmu)
+ return -ENODEV;
+
+ kvm_arm_set_pmu(kvm, arm_pmu);
+ return 0;
+}
+
+static int kvm_arm_pmu_v3_set_pmu(struct kvm_vcpu *vcpu, int pmu_id)
+{
+ struct kvm *kvm = vcpu->kvm;
+ struct arm_pmu_entry *entry;
+ struct arm_pmu *arm_pmu;
+ int ret = -ENXIO;
+
+ lockdep_assert_held(&kvm->arch.config_lock);
+ mutex_lock(&arm_pmus_lock);
+
+ list_for_each_entry(entry, &arm_pmus, entry) {
+ arm_pmu = entry->arm_pmu;
+ if (arm_pmu->pmu.type == pmu_id) {
+ if (kvm_vm_has_ran_once(kvm) ||
+ (kvm->arch.pmu_filter && kvm->arch.arm_pmu != arm_pmu)) {
+ ret = -EBUSY;
+ break;
+ }
+
+ kvm_arm_set_pmu(kvm, arm_pmu);
+ cpumask_copy(kvm->arch.supported_cpus, &arm_pmu->supported_cpus);
+
+ /*
+ * Since a specific PMU is explicitly selected,
+ * PMMIR_EL1.SLOTS is deterministic to the guest.
+ * If KVM_ARM_VCPU_PMU_V3_STRICT is set, snapshot
+ * the value to allow the guest to read it.
+ */
+ if (kvm_vcpu_has_pmuv3_strict(vcpu))
+ kvm->arch.pmmir_slots =
+ FIELD_GET(ARMV8_PMU_SLOTS,
+ arm_pmu->reg_pmmir);
+ ret = 0;
+ break;
+ }
+ }
+
+ mutex_unlock(&arm_pmus_lock);
+ return ret;
+}
+
+static int kvm_arm_pmu_v3_set_nr_counters(struct kvm_vcpu *vcpu, unsigned int n)
+{
+ struct kvm *kvm = vcpu->kvm;
+
+ if (!kvm->arch.arm_pmu)
+ return -EINVAL;
+
+ if (n > kvm_arm_pmu_get_max_counters(kvm))
+ return -EINVAL;
+
+ kvm_arm_set_nr_counters(kvm, n);
+ return 0;
+}
+
+int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
+{
+ struct kvm *kvm = vcpu->kvm;
+
+ lockdep_assert_held(&kvm->arch.config_lock);
+
+ if (!kvm_vcpu_has_pmu(vcpu))
+ return -ENODEV;
+
+ if (vcpu->arch.pmu.created)
+ return -EBUSY;
+
+ switch (attr->attr) {
+ case KVM_ARM_VCPU_PMU_V3_IRQ: {
+ int __user *uaddr = (int __user *)(long)attr->addr;
+ int irq;
+
+ if (!irqchip_in_kernel(kvm))
+ return -EINVAL;
+
+ if (get_user(irq, uaddr))
+ return -EFAULT;
+
+ /* The PMU overflow interrupt can be a PPI or a valid SPI. */
+ if (!(irq_is_ppi(kvm, irq) || irq_is_spi(kvm, irq)))
+ return -EINVAL;
+
+ if (!pmu_irq_is_valid(kvm, irq))
+ return -EINVAL;
+
+ if (kvm_arm_pmu_irq_initialized(vcpu))
+ return -EBUSY;
+
+ kvm_debug("Set kvm ARM PMU irq: %d\n", irq);
+ vcpu->arch.pmu.irq_num = irq;
+ return 0;
+ }
+ case KVM_ARM_VCPU_PMU_V3_FILTER: {
+ u8 pmuver = kvm_arm_pmu_get_pmuver_limit();
+ struct kvm_pmu_event_filter __user *uaddr;
+ struct kvm_pmu_event_filter filter;
+ int nr_events;
+
+ /*
+ * Allow userspace to specify an event filter for the entire
+ * event range supported by PMUVer of the hardware, rather
+ * than the guest's PMUVer for KVM backward compatibility.
+ */
+ nr_events = __kvm_pmu_event_mask(pmuver) + 1;
+
+ uaddr = (struct kvm_pmu_event_filter __user *)(long)attr->addr;
+
+ if (copy_from_user(&filter, uaddr, sizeof(filter)))
+ return -EFAULT;
+
+ if (((u32)filter.base_event + filter.nevents) > nr_events ||
+ (filter.action != KVM_PMU_EVENT_ALLOW &&
+ filter.action != KVM_PMU_EVENT_DENY))
+ return -EINVAL;
+
+ if (kvm_vm_has_ran_once(kvm))
+ return -EBUSY;
+
+ if (!kvm->arch.arm_pmu)
+ return -ENXIO;
+
+ if (!kvm->arch.pmu_filter) {
+ kvm->arch.pmu_filter = bitmap_alloc(nr_events, GFP_KERNEL_ACCOUNT);
+ if (!kvm->arch.pmu_filter)
+ return -ENOMEM;
+
+ /*
+ * The default depends on the first applied filter.
+ * If it allows events, the default is to deny.
+ * Conversely, if the first filter denies a set of
+ * events, the default is to allow.
+ */
+ if (filter.action == KVM_PMU_EVENT_ALLOW)
+ bitmap_zero(kvm->arch.pmu_filter, nr_events);
+ else
+ bitmap_fill(kvm->arch.pmu_filter, nr_events);
+ }
+
+ if (filter.action == KVM_PMU_EVENT_ALLOW)
+ bitmap_set(kvm->arch.pmu_filter, filter.base_event, filter.nevents);
+ else
+ bitmap_clear(kvm->arch.pmu_filter, filter.base_event, filter.nevents);
+
+ return 0;
+ }
+ case KVM_ARM_VCPU_PMU_V3_SET_PMU: {
+ int __user *uaddr = (int __user *)(long)attr->addr;
+ int pmu_id;
+
+ if (get_user(pmu_id, uaddr))
+ return -EFAULT;
+
+ return kvm_arm_pmu_v3_set_pmu(vcpu, pmu_id);
+ }
+ case KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS: {
+ unsigned int __user *uaddr = (unsigned int __user *)(long)attr->addr;
+ unsigned int n;
+
+ if (get_user(n, uaddr))
+ return -EFAULT;
+
+ return kvm_arm_pmu_v3_set_nr_counters(vcpu, n);
+ }
+ case KVM_ARM_VCPU_PMU_V3_INIT:
+ return kvm_arm_pmu_v3_init(vcpu);
+ }
+
+ return -ENXIO;
+}
+
+int kvm_arm_pmu_v3_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
+{
+ switch (attr->attr) {
+ case KVM_ARM_VCPU_PMU_V3_IRQ: {
+ int __user *uaddr = (int __user *)(long)attr->addr;
+ int irq;
+
+ if (!irqchip_in_kernel(vcpu->kvm))
+ return -EINVAL;
+
+ if (!kvm_vcpu_has_pmu(vcpu))
+ return -ENODEV;
+
+ if (!kvm_arm_pmu_irq_initialized(vcpu))
+ return -ENXIO;
+
+ irq = vcpu->arch.pmu.irq_num;
+ return put_user(irq, uaddr);
+ }
+ }
+
+ return -ENXIO;
+}
+
+int kvm_arm_pmu_v3_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
+{
+ switch (attr->attr) {
+ case KVM_ARM_VCPU_PMU_V3_IRQ:
+ case KVM_ARM_VCPU_PMU_V3_INIT:
+ case KVM_ARM_VCPU_PMU_V3_FILTER:
+ case KVM_ARM_VCPU_PMU_V3_SET_PMU:
+ case KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS:
+ if (kvm_vcpu_has_pmu(vcpu))
+ return 0;
+ }
+
+ return -ENXIO;
+}
+
+u8 kvm_arm_pmu_get_pmuver_limit(void)
+{
+ unsigned int pmuver;
+
+ pmuver = SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer,
+ read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1));
+
+ /*
+ * Spoof a barebones PMUv3 implementation if the system supports IMPDEF
+ * traps of the PMUv3 sysregs
+ */
+ if (cpus_have_final_cap(ARM64_WORKAROUND_PMUV3_IMPDEF_TRAPS))
+ return ID_AA64DFR0_EL1_PMUVer_IMP;
+
+ /*
+ * Otherwise, treat IMPLEMENTATION DEFINED functionality as
+ * unimplemented
+ */
+ if (pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF)
+ return 0;
+
+ return min(pmuver, ID_AA64DFR0_EL1_PMUVer_V3P5);
+}
+
+u64 kvm_pmu_implemented_counter_mask(struct kvm_vcpu *vcpu)
+{
+ u64 val = FIELD_GET(ARMV8_PMU_PMCR_N, kvm_vcpu_read_pmcr(vcpu));
+
+ if (val == 0)
+ return BIT(ARMV8_PMU_CYCLE_IDX);
+ else
+ return GENMASK(val - 1, 0) | BIT(ARMV8_PMU_CYCLE_IDX);
+}
+
+u64 kvm_pmu_hyp_counter_mask(struct kvm_vcpu *vcpu)
+{
+ unsigned int hpmn, n;
+
+ if (!vcpu_has_nv(vcpu))
+ return 0;
+
+ hpmn = SYS_FIELD_GET(MDCR_EL2, HPMN, __vcpu_sys_reg(vcpu, MDCR_EL2));
+ n = vcpu->kvm->arch.nr_pmu_counters;
+
+ /*
+ * Programming HPMN to a value greater than PMCR_EL0.N is
+ * CONSTRAINED UNPREDICTABLE. Make the implementation choice that an
+ * UNKNOWN number of counters (in our case, zero) are reserved for EL2.
+ */
+ if (hpmn >= n)
+ return 0;
+
+ /*
+ * Programming HPMN=0 is CONSTRAINED UNPREDICTABLE if FEAT_HPMN0 isn't
+ * implemented. Since KVM's ability to emulate HPMN=0 does not directly
+ * depend on hardware (all PMU registers are trapped), make the
+ * implementation choice that all counters are included in the second
+ * range reserved for EL2/EL3.
+ */
+ return GENMASK(n - 1, hpmn);
+}
+
+bool kvm_pmu_counter_is_hyp(struct kvm_vcpu *vcpu, unsigned int idx)
+{
+ return kvm_pmu_hyp_counter_mask(vcpu) & BIT(idx);
+}
+
+u64 kvm_pmu_accessible_counter_mask(struct kvm_vcpu *vcpu)
+{
+ u64 mask = kvm_pmu_implemented_counter_mask(vcpu);
+
+ if (!vcpu_has_nv(vcpu) || vcpu_is_el2(vcpu))
+ return mask;
+
+ return mask & ~kvm_pmu_hyp_counter_mask(vcpu);
+}
+
+/**
+ * kvm_vcpu_read_pmcr - Read PMCR_EL0 register for the vCPU
+ * @vcpu: The vcpu pointer
+ */
+u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu)
+{
+ u64 pmcr = __vcpu_sys_reg(vcpu, PMCR_EL0);
+ u64 n = vcpu->kvm->arch.nr_pmu_counters;
+
+ if (vcpu_has_nv(vcpu) && !vcpu_is_el2(vcpu))
+ n = FIELD_GET(MDCR_EL2_HPMN, __vcpu_sys_reg(vcpu, MDCR_EL2));
+
+ return u64_replace_bits(pmcr, n, ARMV8_PMU_PMCR_N);
+}
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 93f41ac77c25f..e1bf29de0b6dd 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -50,18 +50,21 @@ struct arm_pmu_entry {
};
bool kvm_supports_guest_pmuv3(void);
-#define kvm_arm_pmu_irq_initialized(v) ((v)->arch.pmu.irq_num != 0)
+#define kvm_arm_pmu_irq_initialized(v) ((v)->arch.pmu.irq_num >= VGIC_NR_SGIS)
u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx);
void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val);
void kvm_pmu_set_counter_value_user(struct kvm_vcpu *vcpu, u64 select_idx, u64 val);
u64 kvm_pmu_implemented_counter_mask(struct kvm_vcpu *vcpu);
+u64 kvm_pmu_hyp_counter_mask(struct kvm_vcpu *vcpu);
u64 kvm_pmu_accessible_counter_mask(struct kvm_vcpu *vcpu);
+u32 kvm_pmu_event_mask(struct kvm *kvm);
u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1);
void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu);
void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu);
void kvm_pmu_reprogram_counter_mask(struct kvm_vcpu *vcpu, u64 val);
void kvm_pmu_flush_hwstate(struct kvm_vcpu *vcpu);
void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu);
+bool kvm_pmu_overflow_status(struct kvm_vcpu *vcpu);
bool kvm_pmu_should_notify_user(struct kvm_vcpu *vcpu);
bool kvm_pmu_update_run(struct kvm_vcpu *vcpu);
void kvm_pmu_software_increment(struct kvm_vcpu *vcpu, u64 val);
@@ -137,6 +140,10 @@ static inline u64 kvm_pmu_accessible_counter_mask(struct kvm_vcpu *vcpu)
{
return 0;
}
+static inline u32 kvm_pmu_event_mask(struct kvm *kvm)
+{
+ return 0;
+}
static inline void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu) {}
static inline void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu) {}
static inline void kvm_pmu_reprogram_counter_mask(struct kvm_vcpu *vcpu, u64 val) {}
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 04/22] perf: arm_pmuv3: Generalize counter bitmasks
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (2 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 03/22] KVM: arm64: Reorganize PMU functions Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 05/22] perf: arm_pmuv3: Move counter allocation mask to per-CPU struct pmu_hw_events Colton Lewis
` (19 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
The OVSR bitmasks are valid for enable and interrupt registers as well as
overflow registers. Generalize the names.
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
drivers/perf/arm_pmuv3.c | 4 ++--
include/linux/perf/arm_pmuv3.h | 14 +++++++-------
tools/include/perf/arm_pmuv3.h | 12 +++++++-----
3 files changed, 16 insertions(+), 14 deletions(-)
diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
index fbd631ec71a65..4a6c1f3bcea1f 100644
--- a/drivers/perf/arm_pmuv3.c
+++ b/drivers/perf/arm_pmuv3.c
@@ -535,7 +535,7 @@ static void armv8pmu_pmcr_write(u64 val)
static int armv8pmu_has_overflowed(u64 pmovsr)
{
- return !!(pmovsr & ARMV8_PMU_OVERFLOWED_MASK);
+ return !!(pmovsr & ARMV8_PMU_CNT_MASK_ALL);
}
static int armv8pmu_counter_has_overflowed(u64 pmnc, int idx)
@@ -771,7 +771,7 @@ static u64 armv8pmu_getreset_flags(void)
value = read_pmovsclr();
/* Write to clear flags */
- value &= ARMV8_PMU_OVERFLOWED_MASK;
+ value &= ARMV8_PMU_CNT_MASK_ALL;
write_pmovsclr(value);
return value;
diff --git a/include/linux/perf/arm_pmuv3.h b/include/linux/perf/arm_pmuv3.h
index d698efba28a27..fd2a34b4a64d1 100644
--- a/include/linux/perf/arm_pmuv3.h
+++ b/include/linux/perf/arm_pmuv3.h
@@ -224,14 +224,14 @@
ARMV8_PMU_PMCR_LC | ARMV8_PMU_PMCR_LP)
/*
- * PMOVSR: counters overflow flag status reg
+ * Counter bitmask layouts for overflow, enable, and interrupts
*/
-#define ARMV8_PMU_OVSR_P GENMASK(30, 0)
-#define ARMV8_PMU_OVSR_C BIT(31)
-#define ARMV8_PMU_OVSR_F BIT_ULL(32) /* arm64 only */
-/* Mask for writable bits is both P and C fields */
-#define ARMV8_PMU_OVERFLOWED_MASK (ARMV8_PMU_OVSR_P | ARMV8_PMU_OVSR_C | \
- ARMV8_PMU_OVSR_F)
+#define ARMV8_PMU_CNT_MASK_P GENMASK(30, 0)
+#define ARMV8_PMU_CNT_MASK_C BIT(31)
+#define ARMV8_PMU_CNT_MASK_F BIT_ULL(32) /* arm64 only */
+#define ARMV8_PMU_CNT_MASK_ALL (ARMV8_PMU_CNT_MASK_P | \
+ ARMV8_PMU_CNT_MASK_C | \
+ ARMV8_PMU_CNT_MASK_F)
/*
* PMXEVTYPER: Event selection reg
diff --git a/tools/include/perf/arm_pmuv3.h b/tools/include/perf/arm_pmuv3.h
index 1e397d55384ed..d045b0f3b93fe 100644
--- a/tools/include/perf/arm_pmuv3.h
+++ b/tools/include/perf/arm_pmuv3.h
@@ -226,12 +226,14 @@
ARMV8_PMU_PMCR_LC | ARMV8_PMU_PMCR_LP)
/*
- * PMOVSR: counters overflow flag status reg
+ * Counter bitmask layouts for overflow, enable, and interrupts
*/
-#define ARMV8_PMU_OVSR_P GENMASK(30, 0)
-#define ARMV8_PMU_OVSR_C BIT(31)
-/* Mask for writable bits is both P and C fields */
-#define ARMV8_PMU_OVERFLOWED_MASK (ARMV8_PMU_OVSR_P | ARMV8_PMU_OVSR_C)
+#define ARMV8_PMU_CNT_MASK_P GENMASK(30, 0)
+#define ARMV8_PMU_CNT_MASK_C BIT(31)
+#define ARMV8_PMU_CNT_MASK_F BIT_ULL(32) /* arm64 only */
+#define ARMV8_PMU_CNT_MASK_ALL (ARMV8_PMU_CNT_MASK_P | \
+ ARMV8_PMU_CNT_MASK_C | \
+ ARMV8_PMU_CNT_MASK_F)
/*
* PMXEVTYPER: Event selection reg
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 05/22] perf: arm_pmuv3: Move counter allocation mask to per-CPU struct pmu_hw_events
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (3 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 04/22] perf: arm_pmuv3: Generalize counter bitmasks Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 06/22] perf: arm_pmuv3: Check cntr_mask before using pmccntr Colton Lewis
` (18 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
In preparation for dynamic per-CPU PMU counter reservations when running
KVM guests with a partitioned PMU, move the counter allocation mask from
the global struct arm_pmu to per-CPU struct pmu_hw_events.
Initialize cpuc->cntr_mask from the static cpu_pmu->cntr_mask during PMU
probe and CPU hotplug startup, and update event counter allocation
helpers (armv8pmu_get_single_idx(), armv8pmu_get_chain_idx(), and
armv8pmu_get_event_idx()) to query the per-CPU mask.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
drivers/perf/arm_pmu.c | 7 ++++++-
drivers/perf/arm_pmuv3.c | 18 +++++++++++++-----
include/linux/perf/arm_pmu.h | 1 +
3 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index 1150695653892..344adcd3521d0 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -408,9 +408,11 @@ validate_group(struct perf_event *event)
/*
* Initialise the fake PMU. We only need to populate the
- * used_mask for the purposes of validation.
+ * used_mask and cntr_mask for the purposes of validation.
*/
memset(&fake_pmu.used_mask, 0, sizeof(fake_pmu.used_mask));
+ bitmap_copy(fake_pmu.cntr_mask, to_arm_pmu(event->pmu)->cntr_mask,
+ ARMPMU_MAX_HWEVENTS);
if (!validate_event(event->pmu, &fake_pmu, leader))
return -EINVAL;
@@ -717,6 +719,7 @@ bool arm_pmu_irq_is_nmi(void)
static int arm_perf_starting_cpu(unsigned int cpu, struct hlist_node *node)
{
struct arm_pmu *pmu = hlist_entry_safe(node, struct arm_pmu, node);
+ struct pmu_hw_events *cpuc = per_cpu_ptr(pmu->hw_events, cpu);
int irq;
if (!cpumask_test_cpu(cpu, &pmu->supported_cpus))
@@ -724,6 +727,8 @@ static int arm_perf_starting_cpu(unsigned int cpu, struct hlist_node *node)
if (pmu->reset)
pmu->reset(pmu);
+ bitmap_copy(cpuc->cntr_mask, pmu->cntr_mask, ARMPMU_MAX_HWEVENTS);
+
irq = armpmu_get_cpu_irq(pmu, cpu);
if (irq)
per_cpu(cpu_irq_ops, cpu)->enable_pmuirq(irq);
diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
index 4a6c1f3bcea1f..49289e5993dd7 100644
--- a/drivers/perf/arm_pmuv3.c
+++ b/drivers/perf/arm_pmuv3.c
@@ -813,7 +813,7 @@ static void armv8pmu_enable_user_access(struct arm_pmu *cpu_pmu)
write_pmuacr(mask);
} else {
/* Clear any unused counters to avoid leaking their contents */
- for_each_andnot_bit(i, cpu_pmu->cntr_mask, cpuc->used_mask,
+ for_each_andnot_bit(i, cpuc->cntr_mask, cpuc->used_mask,
ARMPMU_MAX_HWEVENTS) {
if (i == ARMV8_PMU_CYCLE_IDX)
write_pmccntr(0);
@@ -917,7 +917,7 @@ static irqreturn_t armv8pmu_handle_irq(struct arm_pmu *cpu_pmu)
* to prevent skews in group events.
*/
armv8pmu_stop(cpu_pmu);
- for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMPMU_MAX_HWEVENTS) {
+ for_each_set_bit(idx, cpuc->cntr_mask, ARMPMU_MAX_HWEVENTS) {
struct perf_event *event = cpuc->events[idx];
struct hw_perf_event *hwc;
@@ -958,7 +958,7 @@ static int armv8pmu_get_single_idx(struct pmu_hw_events *cpuc,
{
int idx;
- for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS) {
+ for_each_set_bit(idx, cpuc->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS) {
if (!test_and_set_bit(idx, cpuc->used_mask))
return idx;
}
@@ -974,7 +974,7 @@ static int armv8pmu_get_chain_idx(struct pmu_hw_events *cpuc,
* Chaining requires two consecutive event counters, where
* the lower idx must be even.
*/
- for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS) {
+ for_each_set_bit(idx, cpuc->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS) {
if (!(idx & 0x1))
continue;
if (!test_and_set_bit(idx, cpuc->used_mask)) {
@@ -1042,7 +1042,7 @@ static int armv8pmu_get_event_idx(struct pmu_hw_events *cpuc,
*/
if ((evtype == ARMV8_PMUV3_PERFCTR_INST_RETIRED) &&
!armv8pmu_event_get_threshold(&event->attr) &&
- test_bit(ARMV8_PMU_INSTR_IDX, cpu_pmu->cntr_mask) &&
+ test_bit(ARMV8_PMU_INSTR_IDX, cpuc->cntr_mask) &&
!armv8pmu_event_want_user_access(event)) {
if (!test_and_set_bit(ARMV8_PMU_INSTR_IDX, cpuc->used_mask))
return ARMV8_PMU_INSTR_IDX;
@@ -1426,6 +1426,7 @@ static int armv8pmu_probe_pmu(struct arm_pmu *cpu_pmu)
.present = false,
};
int ret;
+ int cpu;
ret = smp_call_function_any(&cpu_pmu->supported_cpus,
__armv8pmu_probe_pmu,
@@ -1441,6 +1442,13 @@ static int armv8pmu_probe_pmu(struct arm_pmu *cpu_pmu)
if (ret)
return ret;
}
+
+ for_each_possible_cpu(cpu) {
+ struct pmu_hw_events *cpuc = per_cpu_ptr(cpu_pmu->hw_events, cpu);
+
+ bitmap_copy(cpuc->cntr_mask, cpu_pmu->cntr_mask, ARMPMU_MAX_HWEVENTS);
+ }
+
return 0;
}
diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
index 02d2c7f45b527..be1e345e99a77 100644
--- a/include/linux/perf/arm_pmu.h
+++ b/include/linux/perf/arm_pmu.h
@@ -62,6 +62,7 @@ struct pmu_hw_events {
* an event. A 0 means that the counter can be used.
*/
DECLARE_BITMAP(used_mask, ARMPMU_MAX_HWEVENTS);
+ DECLARE_BITMAP(cntr_mask, ARMPMU_MAX_HWEVENTS);
/*
* When using percpu IRQs, we need a percpu dev_id. Place it here as we
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 06/22] perf: arm_pmuv3: Check cntr_mask before using pmccntr
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (4 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 05/22] perf: arm_pmuv3: Move counter allocation mask to per-CPU struct pmu_hw_events Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 07/22] perf: arm_pmuv3: Allocate counter indices from high to low Colton Lewis
` (17 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
When the PMU is partitioned, PMCCNTR_EL0 is reserved for the guest and
removed from cpuc->cntr_mask. Move the PMCCNTR_EL0 availability checks
(cpuc->cntr_mask and cpuc->used_mask) into armv8pmu_can_use_pmccntr()
and un-nest the 64-bit user-access fallback check in
armv8pmu_get_event_idx() so host CPU_CYCLES events fall back to
general-purpose event counters when PMCCNTR_EL0 is unavailable.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
drivers/perf/arm_pmuv3.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
index 49289e5993dd7..c15a34684137a 100644
--- a/drivers/perf/arm_pmuv3.c
+++ b/drivers/perf/arm_pmuv3.c
@@ -1015,6 +1015,10 @@ static bool armv8pmu_can_use_pmccntr(struct pmu_hw_events *cpuc,
if (cpu_pmu->avoid_pmccntr)
return false;
+ if (!test_bit(ARMV8_PMU_CYCLE_IDX, cpuc->cntr_mask) ||
+ test_bit(ARMV8_PMU_CYCLE_IDX, cpuc->used_mask))
+ return false;
+
return true;
}
@@ -1027,14 +1031,15 @@ static int armv8pmu_get_event_idx(struct pmu_hw_events *cpuc,
/* Always prefer to place a cycle counter into the cycle counter. */
if (armv8pmu_can_use_pmccntr(cpuc, event)) {
- if (!test_and_set_bit(ARMV8_PMU_CYCLE_IDX, cpuc->used_mask))
- return ARMV8_PMU_CYCLE_IDX;
- else if (armv8pmu_event_is_64bit(event) &&
- armv8pmu_event_want_user_access(event) &&
- !armv8pmu_has_long_event(cpu_pmu))
- return -EAGAIN;
+ set_bit(ARMV8_PMU_CYCLE_IDX, cpuc->used_mask);
+ return ARMV8_PMU_CYCLE_IDX;
}
+ if (armv8pmu_event_is_64bit(event) &&
+ armv8pmu_event_want_user_access(event) &&
+ !armv8pmu_has_long_event(cpu_pmu))
+ return -EAGAIN;
+
/*
* Always prefer to place a instruction counter into the instruction counter,
* but don't expose the instruction counter to userspace access as userspace
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 07/22] perf: arm_pmuv3: Allocate counter indices from high to low
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (5 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 06/22] perf: arm_pmuv3: Check cntr_mask before using pmccntr Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 08/22] KVM: arm64: Add initial scaffolding for Partitioned PMU Colton Lewis
` (16 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
To minimize collisions between host and guest counters, allocate host
counters from high to low. How the pivot HPMN is defined to partition
the counters gives the guest the low index counters.
Verify both the upper odd counter and lower even counter are present in
cpuc->cntr_mask when allocating 64-bit chained events so that an odd
HPMN boundary does not leak a guest counter into a host chained pair.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
drivers/perf/arm_pmuv3.c | 25 ++++++++++++++++---------
1 file changed, 16 insertions(+), 9 deletions(-)
diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
index c15a34684137a..4fcdae8021a56 100644
--- a/drivers/perf/arm_pmuv3.c
+++ b/drivers/perf/arm_pmuv3.c
@@ -958,10 +958,12 @@ static int armv8pmu_get_single_idx(struct pmu_hw_events *cpuc,
{
int idx;
- for_each_set_bit(idx, cpuc->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS) {
- if (!test_and_set_bit(idx, cpuc->used_mask))
+ for (idx = ARMV8_PMU_MAX_GENERAL_COUNTERS - 1; idx >= 0; idx--) {
+ if (test_bit(idx, cpuc->cntr_mask) &&
+ !test_and_set_bit(idx, cpuc->used_mask))
return idx;
}
+
return -EAGAIN;
}
@@ -974,17 +976,22 @@ static int armv8pmu_get_chain_idx(struct pmu_hw_events *cpuc,
* Chaining requires two consecutive event counters, where
* the lower idx must be even.
*/
- for_each_set_bit(idx, cpuc->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS) {
+ for (idx = ARMV8_PMU_MAX_GENERAL_COUNTERS - 1; idx >= 0; idx--) {
if (!(idx & 0x1))
continue;
- if (!test_and_set_bit(idx, cpuc->used_mask)) {
- /* Check if the preceding even counter is available */
- if (!test_and_set_bit(idx - 1, cpuc->used_mask))
- return idx;
- /* Release the Odd counter */
- clear_bit(idx, cpuc->used_mask);
+
+ if (test_bit(idx, cpuc->cntr_mask) &&
+ test_bit(idx - 1, cpuc->cntr_mask)) {
+ if (!test_and_set_bit(idx, cpuc->used_mask)) {
+ /* Check if the preceding even counter is available */
+ if (!test_and_set_bit(idx - 1, cpuc->used_mask))
+ return idx;
+ /* Release the Odd counter */
+ clear_bit(idx, cpuc->used_mask);
+ }
}
}
+
return -EAGAIN;
}
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 08/22] KVM: arm64: Add initial scaffolding for Partitioned PMU
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (6 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 07/22] perf: arm_pmuv3: Allocate counter indices from high to low Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 09/22] KVM: arm64: Set up FGT " Colton Lewis
` (15 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
Add the foundational helpers for Partitioned PMU support in
arch/arm64/kvm/pmu-direct.c:
- has_host_pmu_partition_support() and has_kvm_pmu_partition_support()
to check VHE and PMUv3 availability.
- kvm_pmu_partition_enable() and kvm_pmu_is_partitioned() to track per-VM
partitioning state via KVM_ARCH_FLAG_PARTITION_PMU_ENABLED.
- kvm_pmu_host_counter_mask() and kvm_pmu_guest_counter_mask() to
compute the bitmasks of host-reserved (HPMN..N-1) and guest-reserved
(0..HPMN-1 and PMCCNTR_EL0) hardware counters.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm/include/asm/arm_pmuv3.h | 8 ++
arch/arm64/include/asm/kvm_host.h | 2 +
arch/arm64/kvm/Makefile | 2 +-
arch/arm64/kvm/pmu-direct.c | 120 ++++++++++++++++++++++++++++++
include/kvm/arm_pmu.h | 32 ++++++++
5 files changed, 163 insertions(+), 1 deletion(-)
create mode 100644 arch/arm64/kvm/pmu-direct.c
diff --git a/arch/arm/include/asm/arm_pmuv3.h b/arch/arm/include/asm/arm_pmuv3.h
index ecfede0c03486..cec26c12bc009 100644
--- a/arch/arm/include/asm/arm_pmuv3.h
+++ b/arch/arm/include/asm/arm_pmuv3.h
@@ -221,12 +221,20 @@ static inline bool kvm_pmu_counter_deferred(struct perf_event_attr *attr)
return false;
}
+static inline bool has_host_pmu_partition_support(void)
+{
+ return false;
+}
static inline bool kvm_set_pmuserenr(u64 val)
{
return false;
}
static inline void kvm_vcpu_pmu_resync_el0(void) {}
+static inline u64 kvm_pmu_host_counter_mask(void)
+{
+ return ~0;
+}
/* PMU Version in DFR Register */
#define ARMV8_PMU_DFR_VER_NI 0
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 217c36af1ca51..98143daab6a55 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -367,6 +367,8 @@ struct kvm_arch {
#define KVM_ARCH_FLAG_WRITABLE_IMP_ID_REGS 10
/* Unhandled SEAs are taken to userspace */
#define KVM_ARCH_FLAG_EXIT_SEA 11
+ /* Partitioned PMU Enabled */
+#define KVM_ARCH_FLAG_PARTITION_PMU_ENABLED 12
unsigned long flags;
/* VM-wide vCPU feature set */
diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
index 59612d2f277c1..0e7b8e65c4c93 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile
@@ -26,7 +26,7 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \
vgic/vgic-its.o vgic/vgic-debug.o vgic/vgic-v3-nested.o \
vgic/vgic-v5.o
-kvm-$(CONFIG_HW_PERF_EVENTS) += pmu-emul.o pmu.o
+kvm-$(CONFIG_HW_PERF_EVENTS) += pmu-emul.o pmu-direct.o pmu.o
kvm-$(CONFIG_ARM64_PTR_AUTH) += pauth.o
kvm-$(CONFIG_PTDUMP_STAGE2_DEBUGFS) += ptdump.o
diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c
new file mode 100644
index 0000000000000..f224b97823ce5
--- /dev/null
+++ b/arch/arm64/kvm/pmu-direct.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 Google LLC
+ * Author: Colton Lewis <coltonlewis@google.com>
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/perf/arm_pmu.h>
+#include <linux/perf/arm_pmuv3.h>
+
+#include <asm/arm_pmuv3.h>
+#include <asm/kvm_emulate.h>
+#include <asm/virt.h>
+
+/**
+ * has_host_pmu_partition_support() - Determine if partitioning is possible
+ *
+ * Partitioning is only supported in VHE mode with PMUv3
+ *
+ * Return: True if partitioning is possible, false otherwise
+ */
+bool has_host_pmu_partition_support(void)
+{
+ return has_vhe() &&
+ system_supports_pmuv3();
+}
+
+/**
+ * has_kvm_pmu_partition_support() - If we can enable/disable partition
+ *
+ * Return: true if allowed, false otherwise.
+ */
+bool has_kvm_pmu_partition_support(void)
+{
+ return has_host_pmu_partition_support() &&
+ kvm_supports_guest_pmuv3();
+}
+
+/**
+ * kvm_pmu_partition_enable() - Enable/disable partition flag
+ * @kvm: Pointer to kvm struct
+ * @enable: Whether to enable or disable
+ *
+ * If we want to enable the partition, the guest is free to grab
+ * hardware by accessing PMU registers. Otherwise, the host maintains
+ * control.
+ */
+void kvm_pmu_partition_enable(struct kvm *kvm, bool enable)
+{
+ if (enable)
+ set_bit(KVM_ARCH_FLAG_PARTITION_PMU_ENABLED, &kvm->arch.flags);
+ else
+ clear_bit(KVM_ARCH_FLAG_PARTITION_PMU_ENABLED, &kvm->arch.flags);
+}
+
+/**
+ * kvm_pmu_is_partitioned() - Determine if KVM has a partitioned PMU
+ * @kvm: Pointer to kvm struct
+ *
+ * Return: True if the KVM PMU is partitioned, false otherwise
+ */
+bool kvm_pmu_is_partitioned(struct kvm *kvm)
+{
+ return kvm && test_bit(KVM_ARCH_FLAG_PARTITION_PMU_ENABLED, &kvm->arch.flags);
+}
+
+/**
+ * kvm_pmu_host_counter_mask() - Compute bitmask of host-reserved counters
+ *
+ * Compute the bitmask that selects the host-reserved counters in the
+ * {PMCNTEN,PMINTEN,PMOVS}{SET,CLR} registers. These are the counters
+ * in HPMN..N-1.
+ *
+ * Return: Bitmask
+ */
+u64 kvm_pmu_host_counter_mask(void)
+{
+ struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
+
+ if (vcpu && kvm_pmu_is_partitioned(vcpu->kvm)) {
+ u8 nr_counters = *host_data_ptr(nr_event_counters);
+ unsigned int guest_counters = vcpu->kvm->arch.nr_pmu_counters;
+
+ if (nr_counters > guest_counters)
+ return GENMASK_ULL(nr_counters - 1, guest_counters);
+ else
+ return 0;
+ }
+
+ return ARMV8_PMU_CNT_MASK_ALL;
+}
+
+static u64 kvm_vcpu_pmu_guest_counter_mask(struct kvm_vcpu *vcpu)
+{
+ if (vcpu && kvm_pmu_is_partitioned(vcpu->kvm)) {
+ u64 mask = ARMV8_PMU_CNT_MASK_C;
+ unsigned int guest_counters = vcpu->kvm->arch.nr_pmu_counters;
+
+ if (guest_counters > 0)
+ mask |= GENMASK_ULL(guest_counters - 1, 0);
+
+ return mask;
+ }
+
+ return 0;
+}
+
+/**
+ * kvm_pmu_guest_counter_mask() - Compute bitmask of guest-reserved counters
+ *
+ * Compute the bitmask that selects the guest-reserved counters in the
+ * {PMCNTEN,PMINTEN,PMOVS}{SET,CLR} registers. These are the event counters
+ * in 0..HPMN-1 and the cycle counter (PMCCNTR_EL0).
+ *
+ * Return: Bitmask
+ */
+u64 kvm_pmu_guest_counter_mask(void)
+{
+ return kvm_vcpu_pmu_guest_counter_mask(kvm_get_running_vcpu());
+}
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index e1bf29de0b6dd..45ed338ee7504 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -50,6 +50,7 @@ struct arm_pmu_entry {
};
bool kvm_supports_guest_pmuv3(void);
+bool has_host_pmu_partition_support(void);
#define kvm_arm_pmu_irq_initialized(v) ((v)->arch.pmu.irq_num >= VGIC_NR_SGIS)
u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx);
void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val);
@@ -94,6 +95,11 @@ void kvm_vcpu_pmu_resync_el0(void);
#define kvm_vcpu_has_pmuv3_strict(vcpu) \
(vcpu_has_feature(vcpu, KVM_ARM_VCPU_PMU_V3_STRICT))
+bool has_kvm_pmu_partition_support(void);
+void kvm_pmu_partition_enable(struct kvm *kvm, bool enable);
+bool kvm_pmu_is_partitioned(struct kvm *kvm);
+u64 kvm_pmu_host_counter_mask(void);
+u64 kvm_pmu_guest_counter_mask(void);
/*
* Updates the vcpu's view of the pmu events for this cpu.
* Must be called before every vcpu run after disabling interrupts, to ensure
@@ -122,12 +128,21 @@ static inline bool kvm_supports_guest_pmuv3(void)
return false;
}
+static inline bool has_host_pmu_partition_support(void)
+{
+ return false;
+}
+
#define kvm_arm_pmu_irq_initialized(v) (false)
static inline u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu,
u64 select_idx)
{
return 0;
}
+static inline bool kvm_pmu_is_partitioned(struct kvm *kvm)
+{
+ return false;
+}
static inline void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu,
u64 select_idx, u64 val) {}
static inline void kvm_pmu_set_counter_value_user(struct kvm_vcpu *vcpu,
@@ -226,6 +241,23 @@ static inline bool kvm_pmu_counter_is_hyp(struct kvm_vcpu *vcpu, unsigned int id
static inline void kvm_pmu_nested_transition(struct kvm_vcpu *vcpu) {}
+static inline u64 kvm_pmu_host_counter_mask(void)
+{
+ return ~0;
+}
+
+static inline u64 kvm_pmu_guest_counter_mask(void)
+{
+ return 0;
+}
+
+static inline bool has_kvm_pmu_partition_support(void)
+{
+ return false;
+}
+
+static inline void kvm_pmu_partition_enable(struct kvm *kvm, bool enable) {}
+
#endif
#endif
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 09/22] KVM: arm64: Set up FGT for Partitioned PMU
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (7 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 08/22] KVM: arm64: Add initial scaffolding for Partitioned PMU Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 10/22] KVM: arm64: Add Partitioned PMU register trap handlers Colton Lewis
` (14 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
In order to gain the best performance benefit from partitioning the
PMU, utilize fine grain traps (FEAT_FGT and FEAT_FGT2) to avoid
trapping common PMU register accesses by the guest to remove that
overhead.
Untrapped:
- PMCR_EL0
- PMUSERENR_EL0
- PMSELR_EL0
- PMCCNTR_EL0
- PMCNTEN_EL0
- PMINTEN_EL1
- PMEVCNTRn_EL0
These are safe to untrap because writing MDCR_EL2.HPMN as this series
will do limits the effect of writes to any of these registers to the
partition of counters 0..HPMN-1. Reads from these registers will not
leak information from between guests as all these registers are
context swapped by a later patch in this series. Reads from these
registers also do not leak any information about the host's hardware
beyond what is promised by PMUv3.
Trapped:
- PMOVS_EL0
- PMEVTYPERn_EL0
- PMCCFILTR_EL0
- PMICNTR_EL0
- PMICFILTR_EL0
- PMCEIDn_EL0
- PMMIR_EL1
PMOVS remains trapped so KVM can track overflow IRQs that will need to
be injected into the guest.
PMICNTR and PMICFILTR remain trapped because KVM is not handling them
yet.
PMEVTYPERn remains trapped so KVM can limit which events guests can
count, such as disallowing counting at EL2. PMCCFILTR and PMICFILTR
are special cases of the same.
PMCEIDn and PMMIR remain trapped because they can leak information
specific to the host hardware implementation.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm64/kvm/config.c | 49 ++++++++++++++++++++++++++++++++++++++---
1 file changed, 46 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kvm/config.c b/arch/arm64/kvm/config.c
index 1053676551aff..f00ef9d598a95 100644
--- a/arch/arm64/kvm/config.c
+++ b/arch/arm64/kvm/config.c
@@ -1708,12 +1708,55 @@ static void __compute_hfgwtr(struct kvm_vcpu *vcpu)
*vcpu_fgt(vcpu, HFGWTR_EL2) |= HFGWTR_EL2_TCR_EL1;
}
+static void __compute_hdfgrtr(struct kvm_vcpu *vcpu)
+{
+ __compute_fgt(vcpu, HDFGRTR_EL2);
+
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ *vcpu_fgt(vcpu, HDFGRTR_EL2) |=
+ (HDFGRTR_EL2_PMOVS |
+ HDFGRTR_EL2_PMCCFILTR_EL0 |
+ HDFGRTR_EL2_PMEVTYPERn_EL0 |
+ HDFGRTR_EL2_PMCEIDn_EL0 |
+ HDFGRTR_EL2_PMMIR_EL1) & ~hdfgrtr_masks.res0;
+ }
+}
+
static void __compute_hdfgwtr(struct kvm_vcpu *vcpu)
{
__compute_fgt(vcpu, HDFGWTR_EL2);
if (is_hyp_ctxt(vcpu))
*vcpu_fgt(vcpu, HDFGWTR_EL2) |= HDFGWTR_EL2_MDSCR_EL1;
+
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ *vcpu_fgt(vcpu, HDFGWTR_EL2) |=
+ (HDFGWTR_EL2_PMOVS |
+ HDFGWTR_EL2_PMCCFILTR_EL0 |
+ HDFGWTR_EL2_PMEVTYPERn_EL0) & ~hdfgwtr_masks.res0;
+ }
+}
+
+static void __compute_hdfgrtr2(struct kvm_vcpu *vcpu)
+{
+ __compute_fgt(vcpu, HDFGRTR2_EL2);
+
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ *vcpu_fgt(vcpu, HDFGRTR2_EL2) &=
+ ~(HDFGRTR2_EL2_nPMICFILTR_EL0 |
+ HDFGRTR2_EL2_nPMICNTR_EL0) | hdfgrtr2_masks.res1;
+ }
+}
+
+static void __compute_hdfgwtr2(struct kvm_vcpu *vcpu)
+{
+ __compute_fgt(vcpu, HDFGWTR2_EL2);
+
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ *vcpu_fgt(vcpu, HDFGWTR2_EL2) &=
+ ~(HDFGWTR2_EL2_nPMICFILTR_EL0 |
+ HDFGWTR2_EL2_nPMICNTR_EL0) | hdfgwtr2_masks.res1;
+ }
}
static void __compute_ich_hfgrtr(struct kvm_vcpu *vcpu)
@@ -1750,7 +1793,7 @@ void kvm_vcpu_load_fgt(struct kvm_vcpu *vcpu)
__compute_fgt(vcpu, HFGRTR_EL2);
__compute_hfgwtr(vcpu);
__compute_fgt(vcpu, HFGITR_EL2);
- __compute_fgt(vcpu, HDFGRTR_EL2);
+ __compute_hdfgrtr(vcpu);
__compute_hdfgwtr(vcpu);
__compute_fgt(vcpu, HAFGRTR_EL2);
@@ -1758,8 +1801,8 @@ void kvm_vcpu_load_fgt(struct kvm_vcpu *vcpu)
__compute_fgt(vcpu, HFGRTR2_EL2);
__compute_fgt(vcpu, HFGWTR2_EL2);
__compute_fgt(vcpu, HFGITR2_EL2);
- __compute_fgt(vcpu, HDFGRTR2_EL2);
- __compute_fgt(vcpu, HDFGWTR2_EL2);
+ __compute_hdfgrtr2(vcpu);
+ __compute_hdfgwtr2(vcpu);
}
if (cpus_have_final_cap(ARM64_HAS_GICV5_CPUIF)) {
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 10/22] KVM: arm64: Add Partitioned PMU register trap handlers
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (8 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 09/22] KVM: arm64: Set up FGT " Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 11/22] KVM: arm64: Set up MDCR_EL2 to handle a Partitioned PMU Colton Lewis
` (13 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
We may want a partitioned PMU but not have FEAT_FGT to untrap the
specific registers that would normally be untrapped. Add handling for
those trapped register accesses that does the right thing if the PMU
is partitioned.
For PMOVSCLR_EL0, clear guest overflow bits in both virtual and physical
registers. For PMEVTYPER and PMCCFILTR, write to the virtual register;
subsequent patches enforce the event filter at vcpu_load() and on
trapped register writes.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm64/kvm/pmu-direct.c | 51 +++++++
arch/arm64/kvm/sys_regs.c | 277 +++++++++++++++++++++++++++++-------
include/kvm/arm_pmu.h | 7 +
3 files changed, 287 insertions(+), 48 deletions(-)
diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c
index f224b97823ce5..5045051e91cd3 100644
--- a/arch/arm64/kvm/pmu-direct.c
+++ b/arch/arm64/kvm/pmu-direct.c
@@ -64,6 +64,57 @@ bool kvm_pmu_is_partitioned(struct kvm *kvm)
return kvm && test_bit(KVM_ARCH_FLAG_PARTITION_PMU_ENABLED, &kvm->arch.flags);
}
+/**
+ * kvm_pmu_direct_pmcr_write() - Handle guest writes to PMCR_EL0
+ * @vcpu: Pointer to vcpu struct
+ * @val: Value written to PMCR_EL0
+ *
+ * Write control bits to physical pmcr_el0 and reset guest-owned general
+ * event counters when PMCR_EL0.P is set.
+ */
+void kvm_pmu_direct_pmcr_write(struct kvm_vcpu *vcpu, u64 val)
+{
+ bool reset_p = val & ARMV8_PMU_PMCR_P;
+ unsigned long mask;
+ int i;
+
+ val &= ~ARMV8_PMU_PMCR_P;
+
+ write_sysreg(val, pmcr_el0);
+
+ if (reset_p) {
+ mask = kvm_pmu_implemented_counter_mask(vcpu) & ~BIT(ARMV8_PMU_CYCLE_IDX);
+
+ if (!vcpu_is_el2(vcpu))
+ mask &= ~kvm_pmu_hyp_counter_mask(vcpu);
+
+ for_each_set_bit(i, &mask, ARMV8_PMU_MAX_GENERAL_COUNTERS)
+ write_pmevcntrn(i, 0);
+ }
+}
+
+/**
+ * kvm_pmu_direct_pmcr_read() - Handle guest reads from PMCR_EL0
+ * @vcpu: Pointer to vcpu struct
+ *
+ * Read physical pmcr_el0 and replace PMCR_EL0.N with the number of
+ * event counters partitioned to the guest.
+ *
+ * Return: Filtered PMCR_EL0 value
+ */
+u64 kvm_pmu_direct_pmcr_read(struct kvm_vcpu *vcpu)
+{
+ u64 n = vcpu->kvm->arch.nr_pmu_counters;
+
+ if (vcpu_has_nv(vcpu) && !vcpu_is_el2(vcpu))
+ n = FIELD_GET(MDCR_EL2_HPMN, __vcpu_sys_reg(vcpu, MDCR_EL2));
+
+ return u64_replace_bits(
+ read_sysreg(pmcr_el0),
+ n,
+ ARMV8_PMU_PMCR_N);
+}
+
/**
* kvm_pmu_host_counter_mask() - Compute bitmask of host-reserved counters
*
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index f7f750b7a91c4..c8210a8b10389 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1092,9 +1092,204 @@ static u64 reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
return __vcpu_sys_reg(vcpu, r->reg);
}
+/**
+ * pmu_reg_write() - Register writes for Partitioned PMU
+ * @vcpu: Pointer to vcpu
+ * @reg: vcpu register
+ * @val: value to write
+ * @set: setting or clearing a mask
+ *
+ * Helper for sys_reg.c register accessor functions.
+ */
+static void pmu_reg_write(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg, u64 val, bool set)
+{
+ unsigned long flags;
+ u64 mask;
+ int idx;
+
+ switch (reg) {
+ case PMCR_EL0:
+ if (kvm_pmu_is_partitioned(vcpu->kvm))
+ kvm_pmu_direct_pmcr_write(vcpu, val);
+ else
+ kvm_pmu_handle_pmcr(vcpu, val);
+ break;
+ case PMSELR_EL0:
+ if (kvm_pmu_is_partitioned(vcpu->kvm))
+ write_sysreg(val, pmselr_el0);
+ __vcpu_assign_sys_reg(vcpu, reg, val);
+ break;
+ case PMEVCNTR0_EL0 ... PMCCNTR_EL0:
+ idx = reg - PMEVCNTR0_EL0;
+
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ if (idx == ARMV8_PMU_CYCLE_IDX)
+ write_sysreg(val, pmccntr_el0);
+ else
+ write_pmevcntrn(idx, val);
+ } else {
+ kvm_pmu_set_counter_value(vcpu, idx, val);
+ }
+ break;
+ case PMEVTYPER0_EL0 ... PMCCFILTR_EL0:
+ idx = reg - PMEVTYPER0_EL0;
+
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ mask = kvm_pmu_evtyper_mask(vcpu->kvm);
+ __vcpu_assign_sys_reg(vcpu, reg, val & mask);
+ } else {
+ kvm_pmu_set_counter_event_type(vcpu, val, idx);
+ kvm_vcpu_pmu_restore_guest(vcpu);
+ }
+ break;
+ case PMCNTENSET_EL0:
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ if (set)
+ write_sysreg(val, pmcntenset_el0);
+ else
+ write_sysreg(val, pmcntenclr_el0);
+ } else {
+ if (set)
+ /* accessing PMCNTENSET_EL0 */
+ __vcpu_rmw_sys_reg(vcpu, PMCNTENSET_EL0, |=, val);
+ else
+ /* accessing PMINTENCLR_EL1 */
+ __vcpu_rmw_sys_reg(vcpu, PMCNTENSET_EL0, &=, ~val);
+
+ kvm_pmu_reprogram_counter_mask(vcpu, val);
+ }
+ break;
+ case PMINTENSET_EL1:
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ if (set)
+ write_sysreg(val, pmintenset_el1);
+ else
+ write_sysreg(val, pmintenclr_el1);
+ } else {
+ if (set)
+ /* accessing PMINTENSET_EL1 */
+ __vcpu_rmw_sys_reg(vcpu, PMINTENSET_EL1, |=, val);
+ else
+ /* accessing PMINTENCLR_EL1 */
+ __vcpu_rmw_sys_reg(vcpu, PMINTENSET_EL1, &=, ~val);
+ }
+ break;
+ case PMOVSSET_EL0:
+ local_irq_save(flags);
+ if (set) {
+ /* accessing PMOVSSET_EL0 */
+ __vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, |=, val);
+ } else {
+ /* accessing PMOVSCLR_EL0 */
+ __vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, &=, ~val);
+ if (kvm_pmu_is_partitioned(vcpu->kvm))
+ write_sysreg(val & kvm_pmu_guest_counter_mask(),
+ pmovsclr_el0);
+ }
+ local_irq_restore(flags);
+ break;
+ case PMUSERENR_EL0:
+ if (kvm_pmu_is_partitioned(vcpu->kvm))
+ write_sysreg(val, pmuserenr_el0);
+ __vcpu_assign_sys_reg(vcpu, reg, val);
+ break;
+ default:
+ WARN_ON(1);
+ break;
+ }
+
+}
+
+/**
+ * pmu_reg_read() - Register reads for Partitioned PMU
+ * @vcpu: Pointer to vcpu
+ * @reg: vcpu register
+ *
+ * Helper for sys_reg.c register accessor functions.
+ *
+ * Return: value read
+ */
+static u64 pmu_reg_read(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
+{
+ unsigned long flags;
+ u64 val = 0;
+ int idx;
+
+ switch (reg) {
+ case PMCR_EL0:
+ if (kvm_pmu_is_partitioned(vcpu->kvm))
+ val = kvm_pmu_direct_pmcr_read(vcpu);
+ else
+ val = kvm_vcpu_read_pmcr(vcpu);
+ break;
+ case PMSELR_EL0:
+ if (kvm_pmu_is_partitioned(vcpu->kvm))
+ val = read_sysreg(pmselr_el0);
+ else
+ val = __vcpu_sys_reg(vcpu, reg);
+ break;
+ case PMEVCNTR0_EL0 ... PMCCNTR_EL0:
+ idx = reg - PMEVCNTR0_EL0;
+
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ if (idx == ARMV8_PMU_CYCLE_IDX)
+ val = read_sysreg(pmccntr_el0);
+ else
+ val = read_pmevcntrn(idx);
+ } else {
+ val = kvm_pmu_get_counter_value(vcpu, idx);
+ }
+ break;
+ case PMEVTYPER0_EL0 ... PMCCFILTR_EL0:
+ val = __vcpu_sys_reg(vcpu, reg);
+ break;
+ case PMCNTENSET_EL0:
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ val = read_sysreg(pmcntenset_el0);
+ val &= kvm_pmu_guest_counter_mask();
+ } else {
+ val = __vcpu_sys_reg(vcpu, reg);
+ }
+ break;
+ case PMINTENSET_EL1:
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ val = read_sysreg(pmintenset_el1);
+ val &= kvm_pmu_guest_counter_mask();
+ } else {
+ val = __vcpu_sys_reg(vcpu, reg);
+ }
+ break;
+ case PMOVSSET_EL0:
+ local_irq_save(flags);
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ u64 hw_ovf = read_sysreg(pmovsset_el0) &
+ kvm_pmu_guest_counter_mask();
+
+ if (hw_ovf) {
+ __vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, |=, hw_ovf);
+ write_sysreg(hw_ovf, pmovsclr_el0);
+ }
+ }
+ val = __vcpu_sys_reg(vcpu, reg);
+ local_irq_restore(flags);
+ break;
+ case PMUSERENR_EL0:
+ if (kvm_pmu_is_partitioned(vcpu->kvm))
+ val = read_sysreg(pmuserenr_el0);
+ else
+ val = __vcpu_sys_reg(vcpu, reg);
+ break;
+ default:
+ WARN_ON(1);
+ break;
+ }
+
+ return val;
+}
+
static bool check_pmu_access_disabled(struct kvm_vcpu *vcpu, u64 flags)
{
- u64 reg = __vcpu_sys_reg(vcpu, PMUSERENR_EL0);
+ u64 reg = pmu_reg_read(vcpu, PMUSERENR_EL0);
bool enabled = (reg & flags) || vcpu_mode_priv(vcpu);
if (!enabled)
@@ -1133,18 +1328,17 @@ static bool access_pmcr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
if (p->is_write) {
/*
- * Only update writeable bits of PMCR (continuing into
- * kvm_pmu_handle_pmcr() as well)
+ * Only update writeable bits of PMCR
*/
- val = kvm_vcpu_read_pmcr(vcpu);
+ val = pmu_reg_read(vcpu, PMCR_EL0);
val &= ~ARMV8_PMU_PMCR_MASK;
val |= p->regval & ARMV8_PMU_PMCR_MASK;
if (!kvm_supports_32bit_el0())
val |= ARMV8_PMU_PMCR_LC;
- kvm_pmu_handle_pmcr(vcpu, val);
+ pmu_reg_write(vcpu, PMCR_EL0, val, 0);
} else {
/* PMCR.P & PMCR.C are RAZ */
- val = kvm_vcpu_read_pmcr(vcpu)
+ val = pmu_reg_read(vcpu, PMCR_EL0)
& ~(ARMV8_PMU_PMCR_P | ARMV8_PMU_PMCR_C);
p->regval = val;
}
@@ -1159,10 +1353,10 @@ static bool access_pmselr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
return false;
if (p->is_write)
- __vcpu_assign_sys_reg(vcpu, PMSELR_EL0, p->regval);
+ pmu_reg_write(vcpu, PMSELR_EL0, p->regval, 0);
else
/* return PMSELR.SEL field */
- p->regval = __vcpu_sys_reg(vcpu, PMSELR_EL0)
+ p->regval = pmu_reg_read(vcpu, PMSELR_EL0)
& PMSELR_EL0_SEL_MASK;
return true;
@@ -1239,6 +1433,7 @@ static bool access_pmu_evcntr(struct kvm_vcpu *vcpu,
struct sys_reg_params *p,
const struct sys_reg_desc *r)
{
+ enum vcpu_sysreg reg;
u64 idx = ~0UL;
if (r->CRn == 9 && r->CRm == 13) {
@@ -1248,7 +1443,7 @@ static bool access_pmu_evcntr(struct kvm_vcpu *vcpu,
return false;
idx = SYS_FIELD_GET(PMSELR_EL0, SEL,
- __vcpu_sys_reg(vcpu, PMSELR_EL0));
+ pmu_reg_read(vcpu, PMSELR_EL0));
} else if (r->Op2 == 0) {
/* PMCCNTR_EL0 */
if (pmu_access_cycle_counter_el0_disabled(vcpu))
@@ -1276,18 +1471,21 @@ static bool access_pmu_evcntr(struct kvm_vcpu *vcpu,
if (!pmu_counter_idx_valid(vcpu, idx))
return false;
+ reg = PMEVCNTR0_EL0 + idx;
+
if (p->is_write) {
if (pmu_access_el0_disabled(vcpu))
return false;
- kvm_pmu_set_counter_value(vcpu, idx, p->regval);
+ pmu_reg_write(vcpu, reg, p->regval, 0);
} else {
- p->regval = kvm_pmu_get_counter_value(vcpu, idx);
+ p->regval = pmu_reg_read(vcpu, reg);
}
return true;
}
+
static bool access_pmu_evtyper(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
const struct sys_reg_desc *r)
{
@@ -1298,7 +1496,7 @@ static bool access_pmu_evtyper(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
if (r->CRn == 9 && r->CRm == 13 && r->Op2 == 1) {
/* PMXEVTYPER_EL0 */
- idx = SYS_FIELD_GET(PMSELR_EL0, SEL, __vcpu_sys_reg(vcpu, PMSELR_EL0));
+ idx = SYS_FIELD_GET(PMSELR_EL0, SEL, pmu_reg_read(vcpu, PMSELR_EL0));
reg = PMEVTYPER0_EL0 + idx;
} else if (r->CRn == 14 && (r->CRm & 12) == 12) {
idx = ((r->CRm & 3) << 3) | (r->Op2 & 7);
@@ -1314,12 +1512,10 @@ static bool access_pmu_evtyper(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
if (!pmu_counter_idx_valid(vcpu, idx))
return false;
- if (p->is_write) {
- kvm_pmu_set_counter_event_type(vcpu, p->regval, idx);
- kvm_vcpu_pmu_restore_guest(vcpu);
- } else {
- p->regval = __vcpu_sys_reg(vcpu, reg);
- }
+ if (p->is_write)
+ pmu_reg_write(vcpu, reg, p->regval, 0);
+ else
+ p->regval = pmu_reg_read(vcpu, reg);
return true;
}
@@ -1353,16 +1549,9 @@ static bool access_pmcnten(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
mask = kvm_pmu_accessible_counter_mask(vcpu);
if (p->is_write) {
val = p->regval & mask;
- if (r->Op2 & 0x1)
- /* accessing PMCNTENSET_EL0 */
- __vcpu_rmw_sys_reg(vcpu, PMCNTENSET_EL0, |=, val);
- else
- /* accessing PMCNTENCLR_EL0 */
- __vcpu_rmw_sys_reg(vcpu, PMCNTENSET_EL0, &=, ~val);
-
- kvm_pmu_reprogram_counter_mask(vcpu, val);
+ pmu_reg_write(vcpu, PMCNTENSET_EL0, val, r->Op2 & 0x1);
} else {
- p->regval = __vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
+ p->regval = pmu_reg_read(vcpu, PMCNTENSET_EL0);
}
return true;
@@ -1371,22 +1560,17 @@ static bool access_pmcnten(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
static bool access_pminten(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
const struct sys_reg_desc *r)
{
- u64 mask = kvm_pmu_accessible_counter_mask(vcpu);
+ u64 val, mask;
if (check_pmu_access_disabled(vcpu, 0))
return false;
+ mask = kvm_pmu_accessible_counter_mask(vcpu);
if (p->is_write) {
- u64 val = p->regval & mask;
-
- if (r->Op2 & 0x1)
- /* accessing PMINTENSET_EL1 */
- __vcpu_rmw_sys_reg(vcpu, PMINTENSET_EL1, |=, val);
- else
- /* accessing PMINTENCLR_EL1 */
- __vcpu_rmw_sys_reg(vcpu, PMINTENSET_EL1, &=, ~val);
+ val = p->regval & mask;
+ pmu_reg_write(vcpu, PMINTENSET_EL1, val, r->Op2 & 0x1);
} else {
- p->regval = __vcpu_sys_reg(vcpu, PMINTENSET_EL1);
+ p->regval = pmu_reg_read(vcpu, PMINTENSET_EL1);
}
return true;
@@ -1453,20 +1637,18 @@ static int set_pmmir(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
static bool access_pmovs(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
const struct sys_reg_desc *r)
{
- u64 mask = kvm_pmu_accessible_counter_mask(vcpu);
+ u64 val, mask;
if (pmu_access_el0_disabled(vcpu))
return false;
+ mask = kvm_pmu_accessible_counter_mask(vcpu);
+
if (p->is_write) {
- if (r->CRm & 0x2)
- /* accessing PMOVSSET_EL0 */
- __vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, |=, (p->regval & mask));
- else
- /* accessing PMOVSCLR_EL0 */
- __vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, &=, ~(p->regval & mask));
+ val = p->regval & mask;
+ pmu_reg_write(vcpu, PMOVSSET_EL0, val, r->CRm & 0x2);
} else {
- p->regval = __vcpu_sys_reg(vcpu, PMOVSSET_EL0);
+ p->regval = pmu_reg_read(vcpu, PMOVSSET_EL0);
}
return true;
@@ -1495,10 +1677,9 @@ static bool access_pmuserenr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
if (!vcpu_mode_priv(vcpu))
return undef_access(vcpu, p, r);
- __vcpu_assign_sys_reg(vcpu, PMUSERENR_EL0,
- (p->regval & ARMV8_PMU_USERENR_MASK));
+ pmu_reg_write(vcpu, PMUSERENR_EL0, p->regval & ARMV8_PMU_USERENR_MASK, 0);
} else {
- p->regval = __vcpu_sys_reg(vcpu, PMUSERENR_EL0)
+ p->regval = pmu_reg_read(vcpu, PMUSERENR_EL0)
& ARMV8_PMU_USERENR_MASK;
}
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 45ed338ee7504..a24788243ac99 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -98,6 +98,8 @@ void kvm_vcpu_pmu_resync_el0(void);
bool has_kvm_pmu_partition_support(void);
void kvm_pmu_partition_enable(struct kvm *kvm, bool enable);
bool kvm_pmu_is_partitioned(struct kvm *kvm);
+void kvm_pmu_direct_pmcr_write(struct kvm_vcpu *vcpu, u64 val);
+u64 kvm_pmu_direct_pmcr_read(struct kvm_vcpu *vcpu);
u64 kvm_pmu_host_counter_mask(void);
u64 kvm_pmu_guest_counter_mask(void);
/*
@@ -143,6 +145,11 @@ static inline bool kvm_pmu_is_partitioned(struct kvm *kvm)
{
return false;
}
+static inline void kvm_pmu_direct_pmcr_write(struct kvm_vcpu *vcpu, u64 val) {}
+static inline u64 kvm_pmu_direct_pmcr_read(struct kvm_vcpu *vcpu)
+{
+ return 0;
+}
static inline void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu,
u64 select_idx, u64 val) {}
static inline void kvm_pmu_set_counter_value_user(struct kvm_vcpu *vcpu,
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 11/22] KVM: arm64: Set up MDCR_EL2 to handle a Partitioned PMU
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (9 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 10/22] KVM: arm64: Add Partitioned PMU register trap handlers Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 12/22] KVM: arm64: Context swap Partitioned PMU guest registers Colton Lewis
` (12 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
Set up MDCR_EL2 to handle a Partitioned PMU. If partitioned, set the
HPME, HPMD, and HCCD bits. If we have the ability to use Fine Grain
Traps (FEAT_FGT) also, unset the TPM and TPMCR bits that trap all PMU
accesses and set HPMN to the correct number of guest counters so
hardware enforces the right values.
Protect vcpu->arch.mdcr_el2 updates with local_irq_save() to prevent
races against PMU interrupt handlers modifying MDCR_EL2.HPME.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm64/kvm/debug.c | 39 +++++++++++++++++++++++++++++++++++----
1 file changed, 35 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index f4d7b12045e8f..a722fd4594e09 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -37,14 +37,16 @@ static int cpu_has_spe(u64 dfr0)
*/
static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
{
- preempt_disable();
+ unsigned long flags;
+
+ local_irq_save(flags);
/*
* This also clears MDCR_EL2_E2PB_MASK and MDCR_EL2_E2TB_MASK
* to disable guest access to the profiling and trace buffers
*/
- vcpu->arch.mdcr_el2 = FIELD_PREP(MDCR_EL2_HPMN,
- *host_data_ptr(nr_event_counters));
+
+ vcpu->arch.mdcr_el2 = FIELD_PREP(MDCR_EL2_HPMN, *host_data_ptr(nr_event_counters));
vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
MDCR_EL2_TPMS |
MDCR_EL2_TTRF |
@@ -52,6 +54,35 @@ static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
MDCR_EL2_TDRA |
MDCR_EL2_TDOSA);
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ u8 nr_guest_cntr = vcpu->kvm->arch.nr_pmu_counters;
+ u64 hpmn = FIELD_GET(MDCR_EL2_HPMN, read_sysreg(mdcr_el2));
+ bool hpme;
+
+ if (hpmn < *host_data_ptr(nr_event_counters))
+ hpme = !!(read_sysreg(mdcr_el2) & MDCR_EL2_HPME);
+ else
+ hpme = !!(read_sysreg(pmcr_el0) & ARMV8_PMU_PMCR_E);
+
+ vcpu->arch.mdcr_el2 |= (MDCR_EL2_HPMD | MDCR_EL2_HCCD);
+ if (hpme)
+ vcpu->arch.mdcr_el2 |= MDCR_EL2_HPME;
+
+ /*
+ * Take out the coarse grain traps if we are using
+ * fine grain traps and enforce counter access with
+ * HPMN.
+ */
+ if (!vcpu_on_unsupported_cpu(vcpu) &&
+ (cpus_have_final_cap(ARM64_HAS_HPMN0) || nr_guest_cntr > 0)) {
+ vcpu->arch.mdcr_el2 &= ~MDCR_EL2_HPMN;
+ vcpu->arch.mdcr_el2 |= FIELD_PREP(MDCR_EL2_HPMN, nr_guest_cntr);
+
+ if (cpus_have_final_cap(ARM64_HAS_FGT))
+ vcpu->arch.mdcr_el2 &= ~(MDCR_EL2_TPM | MDCR_EL2_TPMCR);
+ }
+ }
+
/* Is the VM being debugged by userspace? */
if (vcpu->guest_debug)
/* Route all software debug exceptions to EL2 */
@@ -70,7 +101,7 @@ static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
if (has_vhe())
write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
- preempt_enable();
+ local_irq_restore(flags);
}
void kvm_init_host_debug_data(void)
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 12/22] KVM: arm64: Context swap Partitioned PMU guest registers
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (10 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 11/22] KVM: arm64: Set up MDCR_EL2 to handle a Partitioned PMU Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 13/22] KVM: arm64: Enforce PMU event filter at vcpu_load() Colton Lewis
` (11 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
Save and restore newly untrapped registers that can be directly
accessed by the guest when the PMU is partitioned.
- PMEVCNTRn_EL0
- PMCCNTR_EL0
- PMSELR_EL0
- PMCR_EL0
- PMCNTEN_EL0
- PMINTEN_EL1
If we know we are not partitioned (that is, using the emulated vPMU),
then return immediately. A later patch will make this lazy so the
context swaps don't happen unless the guest has accessed the PMU.
PMEVTYPER is handled in a following patch since we must apply the KVM
event filter before writing values to hardware.
PMOVS guest counters are cleared to avoid the possibility of
generating spurious interrupts when PMINTEN is written. This is fine
because the virtual register for PMOVS is always the canonical value.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm64/kvm/arm.c | 4 +-
arch/arm64/kvm/pmu-direct.c | 153 +++++++++++++++++++++++++++++++++++-
arch/arm64/kvm/sys_regs.c | 6 +-
include/kvm/arm_pmu.h | 5 ++
4 files changed, 164 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 8b080804bc90b..75e0f746623ec 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -714,6 +714,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
if (has_vhe())
kvm_vcpu_load_vhe(vcpu);
kvm_arch_vcpu_load_fp(vcpu);
+ kvm_pmu_load(vcpu);
kvm_vcpu_pmu_restore_guest(vcpu);
if (kvm_arm_is_pvtime_enabled(&vcpu->arch))
kvm_make_request(KVM_REQ_RECORD_STEAL, vcpu);
@@ -755,13 +756,14 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
vcpu_set_flag(vcpu, PKVM_HOST_STATE_DIRTY);
}
+ kvm_pmu_put(vcpu);
+ kvm_vcpu_pmu_restore_host(vcpu);
kvm_vcpu_put_debug(vcpu);
kvm_arch_vcpu_put_fp(vcpu);
if (has_vhe())
kvm_vcpu_put_vhe(vcpu);
kvm_timer_vcpu_put(vcpu);
kvm_vgic_put(vcpu);
- kvm_vcpu_pmu_restore_host(vcpu);
if (vcpu_has_nv(vcpu))
kvm_vcpu_put_hw_mmu(vcpu);
kvm_arm_vmid_clear_active();
diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c
index 5045051e91cd3..92eec0fa33867 100644
--- a/arch/arm64/kvm/pmu-direct.c
+++ b/arch/arm64/kvm/pmu-direct.c
@@ -155,7 +155,6 @@ static u64 kvm_vcpu_pmu_guest_counter_mask(struct kvm_vcpu *vcpu)
return 0;
}
-
/**
* kvm_pmu_guest_counter_mask() - Compute bitmask of guest-reserved counters
*
@@ -169,3 +168,155 @@ u64 kvm_pmu_guest_counter_mask(void)
{
return kvm_vcpu_pmu_guest_counter_mask(kvm_get_running_vcpu());
}
+
+/**
+ * kvm_pmu_load() - Load untrapped PMU registers
+ * @vcpu: Pointer to struct kvm_vcpu
+ *
+ * Load all untrapped PMU registers from the VCPU into the PCPU. Mask
+ * to only bits belonging to guest-reserved counters and leave
+ * host-reserved counters alone in bitmask registers.
+ */
+void kvm_pmu_load(struct kvm_vcpu *vcpu)
+{
+ unsigned long guest_counters;
+ u64 mask;
+ u8 i;
+ u64 val;
+
+ /*
+ * If we aren't guest-owned then we know the guest isn't using
+ * the PMU anyway, so no need to bother with the swap.
+ */
+ if (!kvm_pmu_is_partitioned(vcpu->kvm))
+ return;
+
+ preempt_disable();
+
+ guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
+
+ for_each_set_bit(i, &guest_counters, ARMPMU_MAX_HWEVENTS) {
+ val = __vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i);
+
+ if (i == ARMV8_PMU_CYCLE_IDX)
+ write_pmccntr(val);
+ else
+ write_pmevcntrn(i, val);
+ }
+
+ val = __vcpu_sys_reg(vcpu, PMSELR_EL0);
+ write_sysreg(val, pmselr_el0);
+
+ if (!(vcpu->arch.mdcr_el2 & MDCR_EL2_TPM)) {
+ val = __vcpu_sys_reg(vcpu, PMUSERENR_EL0);
+ write_sysreg(val, pmuserenr_el0);
+ }
+
+ /* Save only the stateful writable bits. */
+ val = __vcpu_sys_reg(vcpu, PMCR_EL0);
+ mask = ARMV8_PMU_PMCR_MASK &
+ ~(ARMV8_PMU_PMCR_P | ARMV8_PMU_PMCR_C);
+ write_sysreg(val & mask, pmcr_el0);
+
+ /*
+ * When handling these:
+ * 1. Apply only the bits for guest counters (indicated by mask)
+ * 2. Use the different registers for set and clear
+ */
+ mask = guest_counters;
+
+ /* Clear the hardware overflow flags so there is no chance of
+ * creating spurious interrupts. The hardware here is never
+ * the canonical version anyway.
+ */
+ write_sysreg(mask, pmovsclr_el0);
+
+ val = __vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
+ write_sysreg(val & mask, pmcntenset_el0);
+ write_sysreg(~val & mask, pmcntenclr_el0);
+
+ val = __vcpu_sys_reg(vcpu, PMINTENSET_EL1);
+ write_sysreg(val & mask, pmintenset_el1);
+ write_sysreg(~val & mask, pmintenclr_el1);
+
+ preempt_enable();
+}
+
+/**
+ * kvm_pmu_put() - Put untrapped PMU registers
+ * @vcpu: Pointer to struct kvm_vcpu
+ *
+ * Put all untrapped PMU registers from the VCPU into the PCPU. Mask
+ * to only bits belonging to guest-reserved counters and leave
+ * host-reserved counters alone in bitmask registers.
+ */
+void kvm_pmu_put(struct kvm_vcpu *vcpu)
+{
+ unsigned long guest_counters;
+ unsigned long flags;
+ u64 mask;
+ u8 i;
+ u64 val;
+
+ /*
+ * If we aren't guest-owned then we know the guest is not
+ * accessing the PMU anyway, so no need to bother with the
+ * swap.
+ */
+ if (!kvm_pmu_is_partitioned(vcpu->kvm))
+ return;
+
+ preempt_disable();
+
+ guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
+ mask = guest_counters;
+
+ /* Mask these to only save the guest relevant bits. */
+ val = read_sysreg(pmcntenset_el0);
+ __vcpu_assign_sys_reg(vcpu, PMCNTENSET_EL0, val & mask);
+
+ val = read_sysreg(pmintenset_el1);
+ __vcpu_assign_sys_reg(vcpu, PMINTENSET_EL1, val & mask);
+
+ /* Stop guest counters and disable interrupts in hardware first. */
+ write_sysreg(mask, pmcntenclr_el0);
+ write_sysreg(mask, pmintenclr_el1);
+ isb();
+
+ for_each_set_bit(i, &guest_counters, ARMPMU_MAX_HWEVENTS) {
+ if (i == ARMV8_PMU_CYCLE_IDX)
+ val = read_pmccntr();
+ else
+ val = read_pmevcntrn(i);
+
+ __vcpu_assign_sys_reg(vcpu, PMEVCNTR0_EL0 + i, val);
+ }
+
+ val = read_sysreg(pmselr_el0);
+ __vcpu_assign_sys_reg(vcpu, PMSELR_EL0, val);
+
+ if (!(vcpu->arch.mdcr_el2 & MDCR_EL2_TPM)) {
+ val = read_sysreg(pmuserenr_el0);
+ __vcpu_assign_sys_reg(vcpu, PMUSERENR_EL0, val);
+ }
+
+ val = read_sysreg(pmcr_el0);
+ __vcpu_rmw_sys_reg(vcpu, PMCR_EL0, &=, ~ARMV8_PMU_PMCR_MASK);
+ __vcpu_rmw_sys_reg(vcpu, PMCR_EL0, |=, val & ARMV8_PMU_PMCR_MASK);
+
+ val = ARMV8_PMU_PMCR_LC;
+ if (pmu && pmu->pmuver >= ID_AA64DFR0_EL1_PMUVer_V3P5)
+ val |= ARMV8_PMU_PMCR_LP;
+ if (vcpu->arch.mdcr_el2 & MDCR_EL2_HPME)
+ val |= ARMV8_PMU_PMCR_E;
+ write_sysreg(val, pmcr_el0);
+
+ /* Save pending guest hardware overflows. */
+ local_irq_save(flags);
+ val = read_sysreg(pmovsset_el0);
+ __vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, |=, val & mask);
+ write_sysreg(val & mask, pmovsclr_el0);
+ local_irq_restore(flags);
+
+ preempt_enable();
+}
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index c8210a8b10389..ebcf52261df65 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1189,7 +1189,8 @@ static void pmu_reg_write(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg, u64 val,
local_irq_restore(flags);
break;
case PMUSERENR_EL0:
- if (kvm_pmu_is_partitioned(vcpu->kvm))
+ if (kvm_pmu_is_partitioned(vcpu->kvm) &&
+ !(vcpu->arch.mdcr_el2 & MDCR_EL2_TPM))
write_sysreg(val, pmuserenr_el0);
__vcpu_assign_sys_reg(vcpu, reg, val);
break;
@@ -1274,7 +1275,8 @@ static u64 pmu_reg_read(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
local_irq_restore(flags);
break;
case PMUSERENR_EL0:
- if (kvm_pmu_is_partitioned(vcpu->kvm))
+ if (kvm_pmu_is_partitioned(vcpu->kvm) &&
+ !(vcpu->arch.mdcr_el2 & MDCR_EL2_TPM))
val = read_sysreg(pmuserenr_el0);
else
val = __vcpu_sys_reg(vcpu, reg);
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index a24788243ac99..2604a6a46d5f3 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -102,6 +102,9 @@ void kvm_pmu_direct_pmcr_write(struct kvm_vcpu *vcpu, u64 val);
u64 kvm_pmu_direct_pmcr_read(struct kvm_vcpu *vcpu);
u64 kvm_pmu_host_counter_mask(void);
u64 kvm_pmu_guest_counter_mask(void);
+void kvm_pmu_load(struct kvm_vcpu *vcpu);
+void kvm_pmu_put(struct kvm_vcpu *vcpu);
+
/*
* Updates the vcpu's view of the pmu events for this cpu.
* Must be called before every vcpu run after disabling interrupts, to ensure
@@ -150,6 +153,8 @@ static inline u64 kvm_pmu_direct_pmcr_read(struct kvm_vcpu *vcpu)
{
return 0;
}
+static inline void kvm_pmu_load(struct kvm_vcpu *vcpu) {}
+static inline void kvm_pmu_put(struct kvm_vcpu *vcpu) {}
static inline void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu,
u64 select_idx, u64 val) {}
static inline void kvm_pmu_set_counter_value_user(struct kvm_vcpu *vcpu,
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 13/22] KVM: arm64: Enforce PMU event filter at vcpu_load()
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (11 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 12/22] KVM: arm64: Context swap Partitioned PMU guest registers Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 14/22] perf: Add perf_pmu_resched_update() Colton Lewis
` (10 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
The KVM API for event filtering says that counters do not count when
blocked by the event filter. To enforce that, the event filter must be
rechecked on every load since it might have changed since the last
time the guest wrote a value. If the event is filtered, exclude
counting at all exception levels before writing the hardware.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm64/kvm/pmu-direct.c | 77 +++++++++++++++++++++++++++++++++++++
arch/arm64/kvm/sys_regs.c | 1 +
include/kvm/arm_pmu.h | 3 ++
3 files changed, 81 insertions(+)
diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c
index 92eec0fa33867..a22c9258c2452 100644
--- a/arch/arm64/kvm/pmu-direct.c
+++ b/arch/arm64/kvm/pmu-direct.c
@@ -169,6 +169,82 @@ u64 kvm_pmu_guest_counter_mask(void)
return kvm_vcpu_pmu_guest_counter_mask(kvm_get_running_vcpu());
}
+/**
+ * kvm_pmu_apply_single_event_filter() - Apply event filter to a single counter
+ * @vcpu: Pointer to vcpu struct
+ * @idx: Counter index
+ *
+ * Compute the filtered event value and write it directly to the hardware register.
+ */
+void kvm_pmu_apply_single_event_filter(struct kvm_vcpu *vcpu, u8 idx)
+{
+ struct arm_pmu *pmu = vcpu->kvm->arch.arm_pmu;
+ u64 guest_counters;
+ u64 evtyper_set = ARMV8_PMU_EXCLUDE_EL0 |
+ ARMV8_PMU_EXCLUDE_EL1;
+ u64 evtyper_clr = ARMV8_PMU_INCLUDE_EL2;
+ bool guest_include_el2;
+ u64 val;
+ u64 evsel;
+
+ if (!pmu || vcpu != kvm_get_running_vcpu())
+ return;
+
+ guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
+ if (!test_bit(idx, (unsigned long *)&guest_counters))
+ return;
+
+ if (idx == ARMV8_PMU_CYCLE_IDX) {
+ val = __vcpu_sys_reg(vcpu, PMCCFILTR_EL0);
+ evsel = ARMV8_PMUV3_PERFCTR_CPU_CYCLES;
+ } else {
+ val = __vcpu_sys_reg(vcpu, PMEVTYPER0_EL0 + idx);
+ evsel = val & kvm_pmu_event_mask(vcpu->kvm);
+ }
+
+ guest_include_el2 = (val & ARMV8_PMU_INCLUDE_EL2);
+ val &= ~evtyper_clr;
+
+ if (unlikely(is_hyp_ctxt(vcpu))) {
+ if (guest_include_el2)
+ val &= ~ARMV8_PMU_EXCLUDE_EL1;
+ else
+ val |= ARMV8_PMU_EXCLUDE_EL1;
+ }
+
+ if (vcpu->kvm->arch.pmu_filter &&
+ !test_bit(evsel, vcpu->kvm->arch.pmu_filter))
+ val |= evtyper_set;
+
+ if (idx == ARMV8_PMU_CYCLE_IDX)
+ write_pmccfiltr(val);
+ else
+ write_pmevtypern(idx, val);
+}
+
+/**
+ * kvm_pmu_apply_event_filter() - Apply event filter to all guest counters
+ * @vcpu: Pointer to vcpu struct
+ *
+ * To uphold the guarantee of the KVM PMU event filter, we must ensure
+ * no counter counts if the event is filtered. Accomplish this by
+ * filtering all exception levels if the event is filtered.
+ */
+static void kvm_pmu_apply_event_filter(struct kvm_vcpu *vcpu)
+{
+ struct arm_pmu *pmu = vcpu->kvm->arch.arm_pmu;
+ unsigned long guest_counters;
+ u8 i;
+
+ if (!pmu)
+ return;
+
+ guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
+
+ for_each_set_bit(i, &guest_counters, ARMPMU_MAX_HWEVENTS)
+ kvm_pmu_apply_single_event_filter(vcpu, i);
+}
+
/**
* kvm_pmu_load() - Load untrapped PMU registers
* @vcpu: Pointer to struct kvm_vcpu
@@ -194,6 +270,7 @@ void kvm_pmu_load(struct kvm_vcpu *vcpu)
preempt_disable();
guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
+ kvm_pmu_apply_event_filter(vcpu);
for_each_set_bit(i, &guest_counters, ARMPMU_MAX_HWEVENTS) {
val = __vcpu_sys_reg(vcpu, PMEVCNTR0_EL0 + i);
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index ebcf52261df65..c4aa6a448b6ca 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1137,6 +1137,7 @@ static void pmu_reg_write(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg, u64 val,
if (kvm_pmu_is_partitioned(vcpu->kvm)) {
mask = kvm_pmu_evtyper_mask(vcpu->kvm);
__vcpu_assign_sys_reg(vcpu, reg, val & mask);
+ kvm_pmu_apply_single_event_filter(vcpu, idx);
} else {
kvm_pmu_set_counter_event_type(vcpu, val, idx);
kvm_vcpu_pmu_restore_guest(vcpu);
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 2604a6a46d5f3..ddbbbb050b9de 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -104,6 +104,7 @@ u64 kvm_pmu_host_counter_mask(void);
u64 kvm_pmu_guest_counter_mask(void);
void kvm_pmu_load(struct kvm_vcpu *vcpu);
void kvm_pmu_put(struct kvm_vcpu *vcpu);
+void kvm_pmu_apply_single_event_filter(struct kvm_vcpu *vcpu, u8 idx);
/*
* Updates the vcpu's view of the pmu events for this cpu.
@@ -263,6 +264,8 @@ static inline u64 kvm_pmu_guest_counter_mask(void)
return 0;
}
+static inline void kvm_pmu_apply_single_event_filter(struct kvm_vcpu *vcpu, u8 idx) {}
+
static inline bool has_kvm_pmu_partition_support(void)
{
return false;
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 14/22] perf: Add perf_pmu_resched_update()
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (12 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 13/22] KVM: arm64: Enforce PMU event filter at vcpu_load() Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 15/22] KVM: arm64: Allow kvm_vcpu_pmu_resync_el0() to resync filters in process context Colton Lewis
` (9 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
To modify PMU guest counter reservations dynamically, the per-CPU
available counter mask must be updated while host perf events are
temporarily scheduled out.
Introduce perf_pmu_resched_update() to update PMU state while holding
cpuctx->ctx.lock in between scheduling perf events out and scheduling
them back in. It accepts a callback invoked between ctx_sched_out() and
perf_event_sched_in(), accomplishing atomic counter mask updates with
minimal perf API expansion.
Refactor ctx_resched() into __ctx_resched() to invoke the callback at
the appropriate point.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
include/linux/perf_event.h | 3 +++
kernel/events/core.c | 31 ++++++++++++++++++++++++++++---
2 files changed, 31 insertions(+), 3 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 5842552294c19..32e3c0d365963 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1242,6 +1242,9 @@ extern int perf_event_task_disable(void);
extern int perf_event_task_enable(void);
extern void perf_pmu_resched(struct pmu *pmu);
+extern void perf_pmu_resched_update(struct pmu *pmu,
+ void (*update)(struct pmu *, void *),
+ void *data);
extern int perf_event_refresh(struct perf_event *event, int refresh);
extern void perf_event_update_userpage(struct perf_event *event);
diff --git a/kernel/events/core.c b/kernel/events/core.c
index db7b76d6b68aa..06d1128d194fa 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2991,9 +2991,10 @@ static void perf_event_sched_in(struct perf_cpu_context *cpuctx,
* event_type is a bit mask of the types of events involved. For CPU events,
* event_type is only either EVENT_PINNED or EVENT_FLEXIBLE.
*/
-static void ctx_resched(struct perf_cpu_context *cpuctx,
- struct perf_event_context *task_ctx,
- struct pmu *pmu, enum event_type_t event_type)
+static void __ctx_resched(struct perf_cpu_context *cpuctx,
+ struct perf_event_context *task_ctx,
+ struct pmu *pmu, enum event_type_t event_type,
+ void (*update)(struct pmu *, void *), void *data)
{
bool cpu_event = !!(event_type & EVENT_CPU);
struct perf_event_pmu_context *epc;
@@ -3029,6 +3030,9 @@ static void ctx_resched(struct perf_cpu_context *cpuctx,
else if (event_type & EVENT_PINNED)
ctx_sched_out(&cpuctx->ctx, pmu, EVENT_FLEXIBLE);
+ if (update)
+ update(pmu, data);
+
perf_event_sched_in(cpuctx, task_ctx, pmu, 0);
for_each_epc(epc, &cpuctx->ctx, pmu, 0)
@@ -3040,6 +3044,27 @@ static void ctx_resched(struct perf_cpu_context *cpuctx,
}
}
+static void ctx_resched(struct perf_cpu_context *cpuctx,
+ struct perf_event_context *task_ctx,
+ struct pmu *pmu, enum event_type_t event_type)
+{
+ __ctx_resched(cpuctx, task_ctx, pmu, event_type, NULL, NULL);
+}
+
+void perf_pmu_resched_update(struct pmu *pmu, void (*update)(struct pmu *, void *), void *data)
+{
+ struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
+ struct perf_event_context *task_ctx = cpuctx->task_ctx;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ perf_ctx_lock(cpuctx, task_ctx);
+ __ctx_resched(cpuctx, task_ctx, pmu, EVENT_ALL|EVENT_CPU, update, data);
+ perf_ctx_unlock(cpuctx, task_ctx);
+ local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(perf_pmu_resched_update);
+
void perf_pmu_resched(struct pmu *pmu)
{
struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 15/22] KVM: arm64: Allow kvm_vcpu_pmu_resync_el0() to resync filters in process context
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (13 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 14/22] perf: Add perf_pmu_resched_update() Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 16/22] KVM: arm64: Apply dynamic guest counter reservations Colton Lewis
` (8 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
Previously, kvm_vcpu_pmu_resync_el0() only scheduled
KVM_REQ_RESYNC_PMU_EL0 when called from interrupt context (such as an
IPI reprogramming host perf events). When perf_pmu_resched_update() is
invoked synchronously from process context during vCPU load/put to
reschedule host events around guest-reserved counters,
armv8pmu_enable_event() calls kvm_set_pmu_events() and
kvm_vcpu_pmu_resync_el0() in process context.
Update kvm_vcpu_pmu_resync_el0() to call kvm_vcpu_pmu_restore_guest()
directly when not in interrupt context so that newly rescheduled host
perf events have their EL0 exclusion filters applied immediately.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm64/kvm/pmu.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c
index 6f60f86fad387..a8214ab52fcb5 100644
--- a/arch/arm64/kvm/pmu.c
+++ b/arch/arm64/kvm/pmu.c
@@ -213,14 +213,17 @@ void kvm_vcpu_pmu_resync_el0(void)
{
struct kvm_vcpu *vcpu;
- if (!has_vhe() || !in_interrupt())
+ if (!has_vhe())
return;
vcpu = kvm_get_running_vcpu();
if (!vcpu)
return;
- kvm_make_request(KVM_REQ_RESYNC_PMU_EL0, vcpu);
+ if (in_interrupt())
+ kvm_make_request(KVM_REQ_RESYNC_PMU_EL0, vcpu);
+ else
+ kvm_vcpu_pmu_restore_guest(vcpu);
}
void kvm_host_pmu_init(struct arm_pmu *pmu)
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 16/22] KVM: arm64: Apply dynamic guest counter reservations
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (14 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 15/22] KVM: arm64: Allow kvm_vcpu_pmu_resync_el0() to resync filters in process context Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-30 15:28 ` James Clark
2026-09-24 17:29 ` [PATCH v9 17/22] KVM: arm64: Implement lazy PMU context swaps Colton Lewis
` (7 subsequent siblings)
23 siblings, 1 reply; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
Reserve and release guest PMU counters dynamically during vCPU load and
put rather than statically at VM creation.
Add kvm_pmu_set_guest_counters() in arch/arm64/kvm/pmu-direct.c, called
from kvm_pmu_load() and kvm_pmu_put(). When the requested guest counter
mask collides with active host events in cpuc->used_mask (or when
releasing counters after squeezing a host event), invoke
perf_pmu_resched_update() with kvm_pmu_update_mask() to update the
per-CPU cpuc->cntr_mask between scheduling host events out and back in;
otherwise update cpuc->cntr_mask directly with interrupts disabled.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm64/kvm/pmu-direct.c | 77 ++++++++++++++++++++++++++++++++++++
include/linux/perf/arm_pmu.h | 1 +
2 files changed, 78 insertions(+)
diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c
index a22c9258c2452..31d5afc44f36e 100644
--- a/arch/arm64/kvm/pmu-direct.c
+++ b/arch/arm64/kvm/pmu-direct.c
@@ -115,6 +115,77 @@ u64 kvm_pmu_direct_pmcr_read(struct kvm_vcpu *vcpu)
ARMV8_PMU_PMCR_N);
}
+/* Callback to update counter mask between perf scheduling */
+static void kvm_pmu_update_mask(struct pmu *pmu, void *data)
+{
+ struct arm_pmu *arm_pmu = to_arm_pmu(pmu);
+ struct pmu_hw_events *cpuc = this_cpu_ptr(arm_pmu->hw_events);
+ unsigned long *new_mask = data;
+
+ bitmap_copy(cpuc->cntr_mask, new_mask, ARMPMU_MAX_HWEVENTS);
+}
+
+/**
+ * kvm_pmu_set_guest_counters() - Handle dynamic counter reservations
+ * @cpu_pmu: struct arm_pmu to potentially modify
+ * @guest_mask: new guest mask for the pmu
+ *
+ * Check if guest counters will interfere with current host events and
+ * call into perf_pmu_resched_update if a reschedule is required.
+ */
+static void kvm_pmu_set_guest_counters(struct arm_pmu *cpu_pmu, u64 guest_mask)
+{
+ struct pmu_hw_events *cpuc = this_cpu_ptr(cpu_pmu->hw_events);
+ DECLARE_BITMAP(guest_bitmap, ARMPMU_MAX_HWEVENTS);
+ DECLARE_BITMAP(new_mask, ARMPMU_MAX_HWEVENTS);
+ unsigned long flags;
+ bool need_resched = false;
+
+ bitmap_from_arr64(guest_bitmap, &guest_mask, ARMPMU_MAX_HWEVENTS);
+ bitmap_copy(new_mask, cpu_pmu->cntr_mask, ARMPMU_MAX_HWEVENTS);
+
+ local_irq_save(flags);
+ if (guest_mask) {
+ /* Subtract guest counters from available host mask */
+ bitmap_andnot(new_mask, new_mask, guest_bitmap, ARMPMU_MAX_HWEVENTS);
+
+ /* Did we collide with an active host event? */
+ if (bitmap_intersects(cpuc->used_mask, guest_bitmap, ARMPMU_MAX_HWEVENTS)) {
+ int idx;
+
+ need_resched = true;
+ cpuc->host_squeezed = true;
+
+ /* Look for pinned events that are about to be preempted */
+ for_each_set_bit(idx, guest_bitmap, ARMPMU_MAX_HWEVENTS) {
+ if (test_bit(idx, cpuc->used_mask) && cpuc->events[idx] &&
+ cpuc->events[idx]->attr.pinned) {
+ pr_warn_once("perf: Pinned host event squeezed out by KVM guest PMU partition\n");
+ break;
+ }
+ }
+ }
+ } else {
+ /*
+ * Restoring to full mask.
+ * Only resched if we previously squeezed an event.
+ */
+ if (cpuc->host_squeezed) {
+ need_resched = true;
+ cpuc->host_squeezed = false;
+ }
+ }
+ if (!need_resched)
+ /* Host was never using guest counters anyway */
+ bitmap_copy(cpuc->cntr_mask, new_mask, ARMPMU_MAX_HWEVENTS);
+ local_irq_restore(flags);
+
+ if (need_resched) {
+ /* Collision: run full perf reschedule */
+ perf_pmu_resched_update(&cpu_pmu->pmu, kvm_pmu_update_mask, new_mask);
+ }
+}
+
/**
* kvm_pmu_host_counter_mask() - Compute bitmask of host-reserved counters
*
@@ -255,6 +326,7 @@ static void kvm_pmu_apply_event_filter(struct kvm_vcpu *vcpu)
*/
void kvm_pmu_load(struct kvm_vcpu *vcpu)
{
+ struct arm_pmu *pmu;
unsigned long guest_counters;
u64 mask;
u8 i;
@@ -269,7 +341,9 @@ void kvm_pmu_load(struct kvm_vcpu *vcpu)
preempt_disable();
+ pmu = vcpu->kvm->arch.arm_pmu;
guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
+ kvm_pmu_set_guest_counters(pmu, guest_counters);
kvm_pmu_apply_event_filter(vcpu);
for_each_set_bit(i, &guest_counters, ARMPMU_MAX_HWEVENTS) {
@@ -329,6 +403,7 @@ void kvm_pmu_load(struct kvm_vcpu *vcpu)
*/
void kvm_pmu_put(struct kvm_vcpu *vcpu)
{
+ struct arm_pmu *pmu;
unsigned long guest_counters;
unsigned long flags;
u64 mask;
@@ -345,6 +420,7 @@ void kvm_pmu_put(struct kvm_vcpu *vcpu)
preempt_disable();
+ pmu = vcpu->kvm->arch.arm_pmu;
guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
mask = guest_counters;
@@ -395,5 +471,6 @@ void kvm_pmu_put(struct kvm_vcpu *vcpu)
write_sysreg(val & mask, pmovsclr_el0);
local_irq_restore(flags);
+ kvm_pmu_set_guest_counters(pmu, 0);
preempt_enable();
}
diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
index be1e345e99a77..45658273ffa86 100644
--- a/include/linux/perf/arm_pmu.h
+++ b/include/linux/perf/arm_pmu.h
@@ -76,6 +76,7 @@ struct pmu_hw_events {
/* Active events requesting branch records */
unsigned int branch_users;
+ bool host_squeezed;
};
enum armpmu_attr_groups {
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* Re: [PATCH v9 16/22] KVM: arm64: Apply dynamic guest counter reservations
2026-09-24 17:29 ` [PATCH v9 16/22] KVM: arm64: Apply dynamic guest counter reservations Colton Lewis
@ 2026-09-30 15:28 ` James Clark
2026-10-01 21:33 ` Colton Lewis
0 siblings, 1 reply; 31+ messages in thread
From: James Clark @ 2026-09-30 15:28 UTC (permalink / raw)
To: Colton Lewis
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel, kvm,
kvmarm, linux-arm-kernel
On 24/09/2026 18:29, Colton Lewis wrote:
> Reserve and release guest PMU counters dynamically during vCPU load and
> put rather than statically at VM creation.
>
> Add kvm_pmu_set_guest_counters() in arch/arm64/kvm/pmu-direct.c, called
> from kvm_pmu_load() and kvm_pmu_put(). When the requested guest counter
> mask collides with active host events in cpuc->used_mask (or when
> releasing counters after squeezing a host event), invoke
> perf_pmu_resched_update() with kvm_pmu_update_mask() to update the
> per-CPU cpuc->cntr_mask between scheduling host events out and back in;
> otherwise update cpuc->cntr_mask directly with interrupts disabled.
>
> Signed-off-by: Colton Lewis <coltonlewis@google.com>
> ---
> arch/arm64/kvm/pmu-direct.c | 77 ++++++++++++++++++++++++++++++++++++
> include/linux/perf/arm_pmu.h | 1 +
> 2 files changed, 78 insertions(+)
>
> diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c
> index a22c9258c2452..31d5afc44f36e 100644
> --- a/arch/arm64/kvm/pmu-direct.c
> +++ b/arch/arm64/kvm/pmu-direct.c
> @@ -115,6 +115,77 @@ u64 kvm_pmu_direct_pmcr_read(struct kvm_vcpu *vcpu)
> ARMV8_PMU_PMCR_N);
> }
>
> +/* Callback to update counter mask between perf scheduling */
> +static void kvm_pmu_update_mask(struct pmu *pmu, void *data)
> +{
> + struct arm_pmu *arm_pmu = to_arm_pmu(pmu);
> + struct pmu_hw_events *cpuc = this_cpu_ptr(arm_pmu->hw_events);
> + unsigned long *new_mask = data;
> +
> + bitmap_copy(cpuc->cntr_mask, new_mask, ARMPMU_MAX_HWEVENTS);
> +}
> +
> +/**
> + * kvm_pmu_set_guest_counters() - Handle dynamic counter reservations
> + * @cpu_pmu: struct arm_pmu to potentially modify
> + * @guest_mask: new guest mask for the pmu
> + *
> + * Check if guest counters will interfere with current host events and
> + * call into perf_pmu_resched_update if a reschedule is required.
> + */
> +static void kvm_pmu_set_guest_counters(struct arm_pmu *cpu_pmu, u64 guest_mask)
> +{
> + struct pmu_hw_events *cpuc = this_cpu_ptr(cpu_pmu->hw_events);
> + DECLARE_BITMAP(guest_bitmap, ARMPMU_MAX_HWEVENTS);
> + DECLARE_BITMAP(new_mask, ARMPMU_MAX_HWEVENTS);
> + unsigned long flags;
> + bool need_resched = false;
> +
> + bitmap_from_arr64(guest_bitmap, &guest_mask, ARMPMU_MAX_HWEVENTS);
> + bitmap_copy(new_mask, cpu_pmu->cntr_mask, ARMPMU_MAX_HWEVENTS);
> +
> + local_irq_save(flags);
> + if (guest_mask) {
> + /* Subtract guest counters from available host mask */
> + bitmap_andnot(new_mask, new_mask, guest_bitmap, ARMPMU_MAX_HWEVENTS);
> +
> + /* Did we collide with an active host event? */
> + if (bitmap_intersects(cpuc->used_mask, guest_bitmap, ARMPMU_MAX_HWEVENTS)) {
> + int idx;
> +
> + need_resched = true;
> + cpuc->host_squeezed = true;
> +
> + /* Look for pinned events that are about to be preempted */
> + for_each_set_bit(idx, guest_bitmap, ARMPMU_MAX_HWEVENTS) {
> + if (test_bit(idx, cpuc->used_mask) && cpuc->events[idx] &&
> + cpuc->events[idx]->attr.pinned) {
> + pr_warn_once("perf: Pinned host event squeezed out by KVM guest PMU partition\n");
If you enable pseudo-NMIs, watchdog_hardlockup_enable() installs the
watchdog using a pinned PMU event. If host userspace also has a pinned
event on the mandatory 1 PMU counter assigned to the host, then a guest
could potentially squeeze out the watchdog.
I'm wondering if we need to prioritise kernel owned events? Or we just
treat them the same as any other event, and with PMU partitioning assume
they can't be guaranteed to be running? I feel like you would expect a
watchdog to be a bit more than best effort though, especially if there
was always a guaranteed counter available to put it on.
I didn't follow it through completely, but it also looks like if the
event gets squeezed it would enter an error state and then never be
re-enabled, even after the guest stops running.
Note, that I think the current ordering means that the watchdog won't
actually get squeezed out because it's created first. But I don't think
we can rely on the ordering as a strong guarantee, and it might get
broken by refactoring in the future.
> + break;
> + }
> + }
> + }
> + } else {
> + /*
> + * Restoring to full mask.
> + * Only resched if we previously squeezed an event.
> + */
> + if (cpuc->host_squeezed) {
> + need_resched = true;
> + cpuc->host_squeezed = false;
> + }
> + }
> + if (!need_resched)
> + /* Host was never using guest counters anyway */
> + bitmap_copy(cpuc->cntr_mask, new_mask, ARMPMU_MAX_HWEVENTS);
> + local_irq_restore(flags);
> +
> + if (need_resched) {
> + /* Collision: run full perf reschedule */
> + perf_pmu_resched_update(&cpu_pmu->pmu, kvm_pmu_update_mask, new_mask);
> + }
> +}
> +
> /**
> * kvm_pmu_host_counter_mask() - Compute bitmask of host-reserved counters
> *
> @@ -255,6 +326,7 @@ static void kvm_pmu_apply_event_filter(struct kvm_vcpu *vcpu)
> */
> void kvm_pmu_load(struct kvm_vcpu *vcpu)
> {
> + struct arm_pmu *pmu;
> unsigned long guest_counters;
> u64 mask;
> u8 i;
> @@ -269,7 +341,9 @@ void kvm_pmu_load(struct kvm_vcpu *vcpu)
>
> preempt_disable();
>
> + pmu = vcpu->kvm->arch.arm_pmu;
> guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
> + kvm_pmu_set_guest_counters(pmu, guest_counters);
> kvm_pmu_apply_event_filter(vcpu);
>
> for_each_set_bit(i, &guest_counters, ARMPMU_MAX_HWEVENTS) {
> @@ -329,6 +403,7 @@ void kvm_pmu_load(struct kvm_vcpu *vcpu)
> */
> void kvm_pmu_put(struct kvm_vcpu *vcpu)
> {
> + struct arm_pmu *pmu;
> unsigned long guest_counters;
> unsigned long flags;
> u64 mask;
> @@ -345,6 +420,7 @@ void kvm_pmu_put(struct kvm_vcpu *vcpu)
>
> preempt_disable();
>
> + pmu = vcpu->kvm->arch.arm_pmu;
> guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
> mask = guest_counters;
>
> @@ -395,5 +471,6 @@ void kvm_pmu_put(struct kvm_vcpu *vcpu)
> write_sysreg(val & mask, pmovsclr_el0);
> local_irq_restore(flags);
>
> + kvm_pmu_set_guest_counters(pmu, 0);
> preempt_enable();
> }
> diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
> index be1e345e99a77..45658273ffa86 100644
> --- a/include/linux/perf/arm_pmu.h
> +++ b/include/linux/perf/arm_pmu.h
> @@ -76,6 +76,7 @@ struct pmu_hw_events {
>
> /* Active events requesting branch records */
> unsigned int branch_users;
> + bool host_squeezed;
> };
>
> enum armpmu_attr_groups {
^ permalink raw reply [flat|nested] 31+ messages in thread* Re: [PATCH v9 16/22] KVM: arm64: Apply dynamic guest counter reservations
2026-09-30 15:28 ` James Clark
@ 2026-10-01 21:33 ` Colton Lewis
0 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-10-01 21:33 UTC (permalink / raw)
To: James Clark
Cc: Colton Lewis, Marc Zyngier, Oliver Upton, Oliver Upton,
Joey Gouly, Suzuki K Poulose, Zenghui Yu, Fuad Tabba,
Catalin Marinas, Will Deacon, Mark Rutland, Paolo Bonzini,
Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Robin Murphy, Zide Chen, Alexandru Elisei,
Ganapatrao Kulkarni, Mingwei Zhang, Jonathan Corbet,
Russell King, Shuah Khan, linux-perf-users, linux-kselftest,
linux-doc, linux-kernel, kvm, kvmarm, linux-arm-kernel
Hi James,
On Wed, Sep 30, 2026 at 04:28:37PM +0100, James Clark wrote:
> If you enable pseudo-NMIs, watchdog_hardlockup_enable() installs the
> watchdog using a pinned PMU event. If host userspace also has a pinned event
> on the mandatory 1 PMU counter assigned to the host, then a guest could
> potentially squeeze out the watchdog.
>
> I'm wondering if we need to prioritise kernel owned events? Or we just treat
> them the same as any other event, and with PMU partitioning assume they
> can't be guaranteed to be running? I feel like you would expect a watchdog
> to be a bit more than best effort though, especially if there was always a
> guaranteed counter available to put it on.
>
> I didn't follow it through completely, but it also looks like if the event
> gets squeezed it would enter an error state and then never be re-enabled,
> even after the guest stops running.
>
> Note, that I think the current ordering means that the watchdog won't
> actually get squeezed out because it's created first. But I don't think we
> can rely on the ordering as a strong guarantee, and it might get broken by
> refactoring in the future.
Good catch. Even without future refactoring, creation order can be
defeated today if /proc/sys/kernel/nmi_watchdog is toggled off and back
on at runtime while a userspace per-CPU pinned event is already open,
giving the re-created watchdog a higher group_index and causing
merge_sched_in() to put it into PERF_EVENT_STATE_ERROR when a
partitioned guest takes PMCCNTR_EL0.
Prioritizing kernel-owned events (!event->owner) ahead of userspace
events in perf_event_groups_cmp() and perf_less_group_idx() guarantees
that a kernel-pinned watchdog always wins the mandatory host counter
over userspace pinned events regardless of creation order. I will look
into adding that for v10.
Thanks,
Colton
^ permalink raw reply [flat|nested] 31+ messages in thread
* [PATCH v9 17/22] KVM: arm64: Implement lazy PMU context swaps
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (15 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 16/22] KVM: arm64: Apply dynamic guest counter reservations Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 18/22] perf: arm_pmuv3: Handle IRQs for Partitioned PMU guest counters Colton Lewis
` (6 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
Since many guests never touch the PMU, avoid paying the cost of
reserving hardware counters and context swapping PMU registers on every
vCPU load and put until the guest actively enables PMU counters or
interrupts.
Track per-vCPU PMU ownership state via enum vcpu_pmu_access
(VCPU_PMU_ACCESS_FREE vs. VCPU_PMU_ACCESS_GUEST_OWNED):
- While FREE, trap all PMU register accesses via MDCR_EL2 (HPMN set to
the full host counter count, TPM/TPMCR set, and FGT traps left at
default) so host perf retains all counters including PMCCNTR_EL0.
Reads and non-enabling writes (such as guest kernel PMU probe resets)
operate on virtual register state without claiming hardware counters.
- When the guest enables counting or interrupts (writing PMCR_EL0.E = 1
or setting guest counter bits in PMCNTENSET_EL0 or PMINTENSET_EL1),
transition to GUEST_OWNED via kvm_pmu_set_guest_owned(), reserve the
guest's partition of counters, load guest PMU state into hardware via
kvm_pmu_load(), and untrap guest partition accesses via FGT.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm64/include/asm/kvm_host.h | 1 +
arch/arm64/include/asm/kvm_types.h | 6 +-
arch/arm64/kvm/debug.c | 4 +-
arch/arm64/kvm/pmu-direct.c | 50 +++++++++++--
arch/arm64/kvm/pmu-emul.c | 6 +-
arch/arm64/kvm/sys_regs.c | 114 ++++++++++++++++++++---------
include/kvm/arm_pmu.h | 10 +++
7 files changed, 146 insertions(+), 45 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 98143daab6a55..8dff576667d10 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1432,6 +1432,7 @@ static inline bool kvm_system_needs_idmapped_vectors(void)
return cpus_have_final_cap(ARM64_SPECTRE_V3A);
}
+void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu);
void kvm_init_host_debug_data(void);
void kvm_debug_init_vhe(void);
void kvm_vcpu_load_debug(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/include/asm/kvm_types.h b/arch/arm64/include/asm/kvm_types.h
index 9a126b9e2d7c9..4e39cbc80aa0b 100644
--- a/arch/arm64/include/asm/kvm_types.h
+++ b/arch/arm64/include/asm/kvm_types.h
@@ -4,5 +4,9 @@
#define KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE 40
-#endif /* _ASM_ARM64_KVM_TYPES_H */
+enum vcpu_pmu_register_access {
+ VCPU_PMU_ACCESS_FREE,
+ VCPU_PMU_ACCESS_GUEST_OWNED,
+};
+#endif /* _ASM_ARM64_KVM_TYPES_H */
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index a722fd4594e09..d74354ec8351f 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -35,7 +35,7 @@ static int cpu_has_spe(u64 dfr0)
* - Self-hosted Trace Filter controls (MDCR_EL2_TTRF)
* - Self-hosted Trace (MDCR_EL2_TTRF/MDCR_EL2_E2TB)
*/
-static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
+void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
{
unsigned long flags;
@@ -54,7 +54,7 @@ static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
MDCR_EL2_TDRA |
MDCR_EL2_TDOSA);
- if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ if (kvm_pmu_is_partitioned(vcpu->kvm) && vcpu->arch.pmu.loaded_on_cpu) {
u8 nr_guest_cntr = vcpu->kvm->arch.nr_pmu_counters;
u64 hpmn = FIELD_GET(MDCR_EL2_HPMN, read_sysreg(mdcr_el2));
bool hpme;
diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c
index 31d5afc44f36e..1ada09d54f68f 100644
--- a/arch/arm64/kvm/pmu-direct.c
+++ b/arch/arm64/kvm/pmu-direct.c
@@ -199,7 +199,7 @@ u64 kvm_pmu_host_counter_mask(void)
{
struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
- if (vcpu && kvm_pmu_is_partitioned(vcpu->kvm)) {
+ if (vcpu && vcpu->arch.pmu.loaded_on_cpu) {
u8 nr_counters = *host_data_ptr(nr_event_counters);
unsigned int guest_counters = vcpu->kvm->arch.nr_pmu_counters;
@@ -212,7 +212,7 @@ u64 kvm_pmu_host_counter_mask(void)
return ARMV8_PMU_CNT_MASK_ALL;
}
-static u64 kvm_vcpu_pmu_guest_counter_mask(struct kvm_vcpu *vcpu)
+u64 kvm_vcpu_pmu_guest_counter_mask(struct kvm_vcpu *vcpu)
{
if (vcpu && kvm_pmu_is_partitioned(vcpu->kvm)) {
u64 mask = ARMV8_PMU_CNT_MASK_C;
@@ -226,6 +226,7 @@ static u64 kvm_vcpu_pmu_guest_counter_mask(struct kvm_vcpu *vcpu)
return 0;
}
+
/**
* kvm_pmu_guest_counter_mask() - Compute bitmask of guest-reserved counters
*
@@ -237,7 +238,12 @@ static u64 kvm_vcpu_pmu_guest_counter_mask(struct kvm_vcpu *vcpu)
*/
u64 kvm_pmu_guest_counter_mask(void)
{
- return kvm_vcpu_pmu_guest_counter_mask(kvm_get_running_vcpu());
+ struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
+
+ if (vcpu && vcpu->arch.pmu.loaded_on_cpu)
+ return kvm_vcpu_pmu_guest_counter_mask(vcpu);
+
+ return 0;
}
/**
@@ -336,7 +342,9 @@ void kvm_pmu_load(struct kvm_vcpu *vcpu)
* If we aren't guest-owned then we know the guest isn't using
* the PMU anyway, so no need to bother with the swap.
*/
- if (!kvm_pmu_is_partitioned(vcpu->kvm))
+ if (!kvm_pmu_is_partitioned(vcpu->kvm) ||
+ kvm_pmu_get_access(vcpu) != VCPU_PMU_ACCESS_GUEST_OWNED ||
+ vcpu->arch.pmu.loaded_on_cpu)
return;
preempt_disable();
@@ -344,6 +352,11 @@ void kvm_pmu_load(struct kvm_vcpu *vcpu)
pmu = vcpu->kvm->arch.arm_pmu;
guest_counters = kvm_vcpu_pmu_guest_counter_mask(vcpu);
kvm_pmu_set_guest_counters(pmu, guest_counters);
+
+ vcpu->arch.pmu.loaded_on_cpu = true;
+ kvm_arm_setup_mdcr_el2(vcpu);
+ isb();
+
kvm_pmu_apply_event_filter(vcpu);
for_each_set_bit(i, &guest_counters, ARMPMU_MAX_HWEVENTS) {
@@ -411,11 +424,12 @@ void kvm_pmu_put(struct kvm_vcpu *vcpu)
u64 val;
/*
- * If we aren't guest-owned then we know the guest is not
+ * If we aren't loaded on the CPU then we know the guest is not
* accessing the PMU anyway, so no need to bother with the
* swap.
*/
- if (!kvm_pmu_is_partitioned(vcpu->kvm))
+ if (!kvm_pmu_is_partitioned(vcpu->kvm) ||
+ !vcpu->arch.pmu.loaded_on_cpu)
return;
preempt_disable();
@@ -471,6 +485,30 @@ void kvm_pmu_put(struct kvm_vcpu *vcpu)
write_sysreg(val & mask, pmovsclr_el0);
local_irq_restore(flags);
+ vcpu->arch.pmu.loaded_on_cpu = false;
+ kvm_arm_setup_mdcr_el2(vcpu);
+ isb();
+
kvm_pmu_set_guest_counters(pmu, 0);
preempt_enable();
}
+
+/**
+ * kvm_pmu_set_guest_owned() - Give PMU ownership to guest
+ * @vcpu: Pointer to vcpu struct
+ *
+ * Reconfigure the guest for physical access of PMU hardware if
+ * allowed. This means reconfiguring mdcr_el2 and loading guest PMU
+ * registers when running on the current physical CPU.
+ */
+void kvm_pmu_set_guest_owned(struct kvm_vcpu *vcpu)
+{
+ guard(preempt)();
+
+ if (kvm_pmu_is_partitioned(vcpu->kvm) &&
+ kvm_pmu_get_access(vcpu) == VCPU_PMU_ACCESS_FREE &&
+ vcpu == kvm_get_running_vcpu()) {
+ vcpu->arch.pmu.access = VCPU_PMU_ACCESS_GUEST_OWNED;
+ kvm_pmu_load(vcpu);
+ }
+}
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 2a2c924fc6b8f..e8195984b0373 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -630,7 +630,8 @@ void kvm_vcpu_reload_pmu(struct kvm_vcpu *vcpu)
__vcpu_rmw_sys_reg(vcpu, PMINTENSET_EL1, &=, mask);
__vcpu_rmw_sys_reg(vcpu, PMCNTENSET_EL0, &=, mask);
- kvm_pmu_reprogram_counter_mask(vcpu, mask);
+ if (!kvm_pmu_is_partitioned(vcpu->kvm))
+ kvm_pmu_reprogram_counter_mask(vcpu, mask);
}
void kvm_pmu_nested_transition(struct kvm_vcpu *vcpu)
@@ -639,6 +640,9 @@ void kvm_pmu_nested_transition(struct kvm_vcpu *vcpu)
unsigned long mask;
int i;
+ if (kvm_pmu_is_partitioned(vcpu->kvm))
+ return;
+
mask = __vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
for_each_set_bit(i, &mask, 32) {
struct kvm_pmc *pmc = kvm_vcpu_idx_to_pmc(vcpu, i);
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index c4aa6a448b6ca..20c46ef705d30 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1109,13 +1109,34 @@ static void pmu_reg_write(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg, u64 val,
switch (reg) {
case PMCR_EL0:
- if (kvm_pmu_is_partitioned(vcpu->kvm))
- kvm_pmu_direct_pmcr_write(vcpu, val);
- else
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ __vcpu_rmw_sys_reg(vcpu, PMCR_EL0, &=, ~ARMV8_PMU_PMCR_MASK);
+ __vcpu_rmw_sys_reg(vcpu, PMCR_EL0, |=, val & ARMV8_PMU_PMCR_MASK);
+ if (val & ARMV8_PMU_PMCR_C)
+ __vcpu_assign_sys_reg(vcpu, PMCCNTR_EL0, 0);
+ if (val & ARMV8_PMU_PMCR_P) {
+ int i;
+
+ mask = kvm_pmu_implemented_counter_mask(vcpu) &
+ ~BIT(ARMV8_PMU_CYCLE_IDX);
+ if (!vcpu_is_el2(vcpu))
+ mask &= ~kvm_pmu_hyp_counter_mask(vcpu);
+ for_each_set_bit(i, (unsigned long *)&mask,
+ ARMV8_PMU_MAX_GENERAL_COUNTERS)
+ __vcpu_assign_sys_reg(vcpu, PMEVCNTR0_EL0 + i, 0);
+ }
+
+ if (val & ARMV8_PMU_PMCR_E)
+ kvm_pmu_set_guest_owned(vcpu);
+
+ if (vcpu->arch.pmu.loaded_on_cpu)
+ kvm_pmu_direct_pmcr_write(vcpu, val);
+ } else {
kvm_pmu_handle_pmcr(vcpu, val);
+ }
break;
case PMSELR_EL0:
- if (kvm_pmu_is_partitioned(vcpu->kvm))
+ if (vcpu->arch.pmu.loaded_on_cpu)
write_sysreg(val, pmselr_el0);
__vcpu_assign_sys_reg(vcpu, reg, val);
break;
@@ -1123,10 +1144,13 @@ static void pmu_reg_write(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg, u64 val,
idx = reg - PMEVCNTR0_EL0;
if (kvm_pmu_is_partitioned(vcpu->kvm)) {
- if (idx == ARMV8_PMU_CYCLE_IDX)
- write_sysreg(val, pmccntr_el0);
- else
- write_pmevcntrn(idx, val);
+ __vcpu_assign_sys_reg(vcpu, reg, val);
+ if (vcpu->arch.pmu.loaded_on_cpu) {
+ if (idx == ARMV8_PMU_CYCLE_IDX)
+ write_sysreg(val, pmccntr_el0);
+ else
+ write_pmevcntrn(idx, val);
+ }
} else {
kvm_pmu_set_counter_value(vcpu, idx, val);
}
@@ -1137,7 +1161,8 @@ static void pmu_reg_write(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg, u64 val,
if (kvm_pmu_is_partitioned(vcpu->kvm)) {
mask = kvm_pmu_evtyper_mask(vcpu->kvm);
__vcpu_assign_sys_reg(vcpu, reg, val & mask);
- kvm_pmu_apply_single_event_filter(vcpu, idx);
+ if (vcpu->arch.pmu.loaded_on_cpu)
+ kvm_pmu_apply_single_event_filter(vcpu, idx);
} else {
kvm_pmu_set_counter_event_type(vcpu, val, idx);
kvm_vcpu_pmu_restore_guest(vcpu);
@@ -1145,16 +1170,24 @@ static void pmu_reg_write(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg, u64 val,
break;
case PMCNTENSET_EL0:
if (kvm_pmu_is_partitioned(vcpu->kvm)) {
- if (set)
- write_sysreg(val, pmcntenset_el0);
- else
- write_sysreg(val, pmcntenclr_el0);
+ mask = kvm_vcpu_pmu_guest_counter_mask(vcpu);
+ if (set) {
+ __vcpu_rmw_sys_reg(vcpu, PMCNTENSET_EL0, |=, val & mask);
+ if (val & mask)
+ kvm_pmu_set_guest_owned(vcpu);
+ if (vcpu->arch.pmu.loaded_on_cpu)
+ write_sysreg(val & mask, pmcntenset_el0);
+ } else {
+ __vcpu_rmw_sys_reg(vcpu, PMCNTENSET_EL0, &=, ~(val & mask));
+ if (vcpu->arch.pmu.loaded_on_cpu)
+ write_sysreg(val & mask, pmcntenclr_el0);
+ }
} else {
if (set)
/* accessing PMCNTENSET_EL0 */
__vcpu_rmw_sys_reg(vcpu, PMCNTENSET_EL0, |=, val);
else
- /* accessing PMINTENCLR_EL1 */
+ /* accessing PMCNTENCLR_EL0 */
__vcpu_rmw_sys_reg(vcpu, PMCNTENSET_EL0, &=, ~val);
kvm_pmu_reprogram_counter_mask(vcpu, val);
@@ -1162,10 +1195,18 @@ static void pmu_reg_write(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg, u64 val,
break;
case PMINTENSET_EL1:
if (kvm_pmu_is_partitioned(vcpu->kvm)) {
- if (set)
- write_sysreg(val, pmintenset_el1);
- else
- write_sysreg(val, pmintenclr_el1);
+ mask = kvm_vcpu_pmu_guest_counter_mask(vcpu);
+ if (set) {
+ __vcpu_rmw_sys_reg(vcpu, PMINTENSET_EL1, |=, val & mask);
+ if (val & mask)
+ kvm_pmu_set_guest_owned(vcpu);
+ if (vcpu->arch.pmu.loaded_on_cpu)
+ write_sysreg(val & mask, pmintenset_el1);
+ } else {
+ __vcpu_rmw_sys_reg(vcpu, PMINTENSET_EL1, &=, ~(val & mask));
+ if (vcpu->arch.pmu.loaded_on_cpu)
+ write_sysreg(val & mask, pmintenclr_el1);
+ }
} else {
if (set)
/* accessing PMINTENSET_EL1 */
@@ -1183,14 +1224,14 @@ static void pmu_reg_write(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg, u64 val,
} else {
/* accessing PMOVSCLR_EL0 */
__vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, &=, ~val);
- if (kvm_pmu_is_partitioned(vcpu->kvm))
- write_sysreg(val & kvm_pmu_guest_counter_mask(),
+ if (vcpu->arch.pmu.loaded_on_cpu)
+ write_sysreg(val & kvm_vcpu_pmu_guest_counter_mask(vcpu),
pmovsclr_el0);
}
local_irq_restore(flags);
break;
case PMUSERENR_EL0:
- if (kvm_pmu_is_partitioned(vcpu->kvm) &&
+ if (vcpu->arch.pmu.loaded_on_cpu &&
!(vcpu->arch.mdcr_el2 & MDCR_EL2_TPM))
write_sysreg(val, pmuserenr_el0);
__vcpu_assign_sys_reg(vcpu, reg, val);
@@ -1199,7 +1240,6 @@ static void pmu_reg_write(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg, u64 val,
WARN_ON(1);
break;
}
-
}
/**
@@ -1219,13 +1259,13 @@ static u64 pmu_reg_read(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
switch (reg) {
case PMCR_EL0:
- if (kvm_pmu_is_partitioned(vcpu->kvm))
+ if (vcpu->arch.pmu.loaded_on_cpu)
val = kvm_pmu_direct_pmcr_read(vcpu);
else
val = kvm_vcpu_read_pmcr(vcpu);
break;
case PMSELR_EL0:
- if (kvm_pmu_is_partitioned(vcpu->kvm))
+ if (vcpu->arch.pmu.loaded_on_cpu)
val = read_sysreg(pmselr_el0);
else
val = __vcpu_sys_reg(vcpu, reg);
@@ -1234,10 +1274,14 @@ static u64 pmu_reg_read(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
idx = reg - PMEVCNTR0_EL0;
if (kvm_pmu_is_partitioned(vcpu->kvm)) {
- if (idx == ARMV8_PMU_CYCLE_IDX)
- val = read_sysreg(pmccntr_el0);
- else
- val = read_pmevcntrn(idx);
+ if (vcpu->arch.pmu.loaded_on_cpu) {
+ if (idx == ARMV8_PMU_CYCLE_IDX)
+ val = read_sysreg(pmccntr_el0);
+ else
+ val = read_pmevcntrn(idx);
+ } else {
+ val = __vcpu_sys_reg(vcpu, reg);
+ }
} else {
val = kvm_pmu_get_counter_value(vcpu, idx);
}
@@ -1246,26 +1290,26 @@ static u64 pmu_reg_read(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
val = __vcpu_sys_reg(vcpu, reg);
break;
case PMCNTENSET_EL0:
- if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ if (vcpu->arch.pmu.loaded_on_cpu) {
val = read_sysreg(pmcntenset_el0);
- val &= kvm_pmu_guest_counter_mask();
+ val &= kvm_vcpu_pmu_guest_counter_mask(vcpu);
} else {
val = __vcpu_sys_reg(vcpu, reg);
}
break;
case PMINTENSET_EL1:
- if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ if (vcpu->arch.pmu.loaded_on_cpu) {
val = read_sysreg(pmintenset_el1);
- val &= kvm_pmu_guest_counter_mask();
+ val &= kvm_vcpu_pmu_guest_counter_mask(vcpu);
} else {
val = __vcpu_sys_reg(vcpu, reg);
}
break;
case PMOVSSET_EL0:
local_irq_save(flags);
- if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ if (vcpu->arch.pmu.loaded_on_cpu) {
u64 hw_ovf = read_sysreg(pmovsset_el0) &
- kvm_pmu_guest_counter_mask();
+ kvm_vcpu_pmu_guest_counter_mask(vcpu);
if (hw_ovf) {
__vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, |=, hw_ovf);
@@ -1276,7 +1320,7 @@ static u64 pmu_reg_read(struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
local_irq_restore(flags);
break;
case PMUSERENR_EL0:
- if (kvm_pmu_is_partitioned(vcpu->kvm) &&
+ if (vcpu->arch.pmu.loaded_on_cpu &&
!(vcpu->arch.mdcr_el2 & MDCR_EL2_TPM))
val = read_sysreg(pmuserenr_el0);
else
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index ddbbbb050b9de..0f2e39367d637 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -7,6 +7,7 @@
#ifndef __ASM_ARM_KVM_PMU_H
#define __ASM_ARM_KVM_PMU_H
+#include <linux/kvm_types.h>
#include <linux/perf_event.h>
#include <linux/perf/arm_pmuv3.h>
#include <linux/perf/arm_pmu.h>
@@ -42,6 +43,8 @@ struct kvm_pmu {
struct kvm_pmc pmc[KVM_ARMV8_PMU_MAX_COUNTERS];
int irq_num;
bool created;
+ bool loaded_on_cpu;
+ enum vcpu_pmu_register_access access;
};
struct arm_pmu_entry {
@@ -100,12 +103,16 @@ void kvm_pmu_partition_enable(struct kvm *kvm, bool enable);
bool kvm_pmu_is_partitioned(struct kvm *kvm);
void kvm_pmu_direct_pmcr_write(struct kvm_vcpu *vcpu, u64 val);
u64 kvm_pmu_direct_pmcr_read(struct kvm_vcpu *vcpu);
+u64 kvm_vcpu_pmu_guest_counter_mask(struct kvm_vcpu *vcpu);
u64 kvm_pmu_host_counter_mask(void);
u64 kvm_pmu_guest_counter_mask(void);
void kvm_pmu_load(struct kvm_vcpu *vcpu);
void kvm_pmu_put(struct kvm_vcpu *vcpu);
+void kvm_pmu_set_guest_owned(struct kvm_vcpu *vcpu);
void kvm_pmu_apply_single_event_filter(struct kvm_vcpu *vcpu, u8 idx);
+#define kvm_pmu_get_access(vcpu) ((vcpu)->arch.pmu.access)
+
/*
* Updates the vcpu's view of the pmu events for this cpu.
* Must be called before every vcpu run after disabling interrupts, to ensure
@@ -149,6 +156,8 @@ static inline bool kvm_pmu_is_partitioned(struct kvm *kvm)
{
return false;
}
+
+#define kvm_pmu_get_access(vcpu) (VCPU_PMU_ACCESS_FREE)
static inline void kvm_pmu_direct_pmcr_write(struct kvm_vcpu *vcpu, u64 val) {}
static inline u64 kvm_pmu_direct_pmcr_read(struct kvm_vcpu *vcpu)
{
@@ -156,6 +165,7 @@ static inline u64 kvm_pmu_direct_pmcr_read(struct kvm_vcpu *vcpu)
}
static inline void kvm_pmu_load(struct kvm_vcpu *vcpu) {}
static inline void kvm_pmu_put(struct kvm_vcpu *vcpu) {}
+static inline void kvm_pmu_set_guest_owned(struct kvm_vcpu *vcpu) {}
static inline void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu,
u64 select_idx, u64 val) {}
static inline void kvm_pmu_set_counter_value_user(struct kvm_vcpu *vcpu,
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 18/22] perf: arm_pmuv3: Handle IRQs for Partitioned PMU guest counters
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (16 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 17/22] KVM: arm64: Implement lazy PMU context swaps Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 19/22] KVM: arm64: Detect overflows for the Partitioned PMU Colton Lewis
` (5 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
Because ARM hardware is not yet capable of direct PPI injection into
guests, guest counters trigger physical PMU interrupts that must be
handled by the host PMU interrupt handler.
In armv8pmu_handle_irq(), clear the overflow flags in hardware for host
counters, restrict host perf event handling to bits in cpuc->cntr_mask,
and pass the overflow flags to kvm_pmu_handle_guest_irq(). The KVM hook
clears the guest counter overflow flags in hardware and records them in
the running vCPU's virtual PMOVSSET_EL0 register for subsequent guest
interrupt injection.
Additionally, provide kvm_pmu_host_start() and kvm_pmu_host_stop() so
that armv8pmu_start() and armv8pmu_stop() toggle MDCR_EL2.HPME rather
than PMCR_EL0.E when a partitioned guest's PMU state is loaded on the
CPU.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm/include/asm/arm_pmuv3.h | 8 ++++
arch/arm64/include/asm/arm_pmuv3.h | 5 +++
arch/arm64/kvm/pmu-direct.c | 67 ++++++++++++++++++++++++++++++
drivers/perf/arm_pmuv3.c | 34 ++++++++-------
include/kvm/arm_pmu.h | 6 +++
5 files changed, 104 insertions(+), 16 deletions(-)
diff --git a/arch/arm/include/asm/arm_pmuv3.h b/arch/arm/include/asm/arm_pmuv3.h
index cec26c12bc009..9b8d6bbbe70cf 100644
--- a/arch/arm/include/asm/arm_pmuv3.h
+++ b/arch/arm/include/asm/arm_pmuv3.h
@@ -180,6 +180,11 @@ static inline void write_pmintenset(u32 val)
write_sysreg(val, PMINTENSET);
}
+static inline u32 read_pmintenset(void)
+{
+ return read_sysreg(PMINTENSET);
+}
+
static inline void write_pmintenclr(u32 val)
{
write_sysreg(val, PMINTENCLR);
@@ -235,6 +240,9 @@ static inline u64 kvm_pmu_host_counter_mask(void)
{
return ~0;
}
+static inline void kvm_pmu_handle_guest_irq(u64 pmovsr) {}
+static inline bool kvm_pmu_host_start(void) { return false; }
+static inline bool kvm_pmu_host_stop(void) { return false; }
/* PMU Version in DFR Register */
#define ARMV8_PMU_DFR_VER_NI 0
diff --git a/arch/arm64/include/asm/arm_pmuv3.h b/arch/arm64/include/asm/arm_pmuv3.h
index cf2b2212e00a2..9037a28365951 100644
--- a/arch/arm64/include/asm/arm_pmuv3.h
+++ b/arch/arm64/include/asm/arm_pmuv3.h
@@ -110,6 +110,11 @@ static inline void write_pmintenset(u64 val)
write_sysreg(val, pmintenset_el1);
}
+static inline u64 read_pmintenset(void)
+{
+ return read_sysreg(pmintenset_el1);
+}
+
static inline void write_pmintenclr(u64 val)
{
write_sysreg(val, pmintenclr_el1);
diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c
index 1ada09d54f68f..95b5a64052762 100644
--- a/arch/arm64/kvm/pmu-direct.c
+++ b/arch/arm64/kvm/pmu-direct.c
@@ -512,3 +512,70 @@ void kvm_pmu_set_guest_owned(struct kvm_vcpu *vcpu)
kvm_pmu_load(vcpu);
}
}
+
+/**
+ * kvm_pmu_handle_guest_irq() - Record IRQs in guest counters
+ * @pmovsr: Overflow flags reported by driver
+ *
+ * Set overflow flags in guest-reserved counters in the VCPU register
+ * for the guest to clear later.
+ */
+void kvm_pmu_handle_guest_irq(u64 pmovsr)
+{
+ struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
+ u64 mask = kvm_pmu_guest_counter_mask();
+ u64 govf = pmovsr & mask;
+ int i;
+
+ write_pmovsclr(govf);
+
+ if (!vcpu || !vcpu->arch.pmu.loaded_on_cpu)
+ return;
+
+ for_each_set_bit(i, (unsigned long *)&govf, 64)
+ set_bit(i, (unsigned long *)__ctxt_sys_reg(&vcpu->arch.ctxt, PMOVSSET_EL0));
+}
+
+/**
+ * kvm_pmu_host_start() - Enable host PMU counters while guest owns PMU
+ *
+ * When a partitioned guest owns the PMU, host counters (HPMN..N-1) are
+ * gated by MDCR_EL2.HPME rather than PMCR_EL0.E.
+ *
+ * Return: True if handled via MDCR_EL2.HPME, false if caller should use PMCR_EL0.E
+ */
+bool kvm_pmu_host_start(void)
+{
+ struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
+
+ if (!vcpu || !kvm_pmu_is_partitioned(vcpu->kvm) ||
+ !vcpu->arch.pmu.loaded_on_cpu)
+ return false;
+
+ vcpu->arch.mdcr_el2 |= MDCR_EL2_HPME;
+ write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
+ isb();
+ return true;
+}
+
+/**
+ * kvm_pmu_host_stop() - Disable host PMU counters while guest owns PMU
+ *
+ * When a partitioned guest owns the PMU, host counters (HPMN..N-1) are
+ * gated by MDCR_EL2.HPME rather than PMCR_EL0.E.
+ *
+ * Return: True if handled via MDCR_EL2.HPME, false if caller should use PMCR_EL0.E
+ */
+bool kvm_pmu_host_stop(void)
+{
+ struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
+
+ if (!vcpu || !kvm_pmu_is_partitioned(vcpu->kvm) ||
+ !vcpu->arch.pmu.loaded_on_cpu)
+ return false;
+
+ vcpu->arch.mdcr_el2 &= ~MDCR_EL2_HPME;
+ write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
+ isb();
+ return true;
+}
diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
index 4fcdae8021a56..3e5f8207a0fee 100644
--- a/drivers/perf/arm_pmuv3.c
+++ b/drivers/perf/arm_pmuv3.c
@@ -763,18 +763,9 @@ static void armv8pmu_disable_event_irq(struct perf_event *event)
armv8pmu_disable_intens(BIT(event->hw.idx));
}
-static u64 armv8pmu_getreset_flags(void)
+static u64 armv8pmu_getovf_flags(void)
{
- u64 value;
-
- /* Read */
- value = read_pmovsclr();
-
- /* Write to clear flags */
- value &= ARMV8_PMU_CNT_MASK_ALL;
- write_pmovsclr(value);
-
- return value;
+ return read_pmovsclr() & ARMV8_PMU_CNT_MASK_ALL;
}
static void update_pmuserenr(u64 val)
@@ -864,7 +855,8 @@ static void armv8pmu_start(struct arm_pmu *cpu_pmu)
brbe_enable(cpu_pmu);
/* Enable all counters */
- armv8pmu_pmcr_write(armv8pmu_pmcr_read() | ARMV8_PMU_PMCR_E);
+ if (!kvm_pmu_host_start())
+ armv8pmu_pmcr_write(armv8pmu_pmcr_read() | ARMV8_PMU_PMCR_E);
}
static void armv8pmu_stop(struct arm_pmu *cpu_pmu)
@@ -875,7 +867,8 @@ static void armv8pmu_stop(struct arm_pmu *cpu_pmu)
brbe_disable();
/* Disable all counters */
- armv8pmu_pmcr_write(armv8pmu_pmcr_read() & ~ARMV8_PMU_PMCR_E);
+ if (!kvm_pmu_host_stop())
+ armv8pmu_pmcr_write(armv8pmu_pmcr_read() & ~ARMV8_PMU_PMCR_E);
}
static void read_branch_records(struct pmu_hw_events *cpuc,
@@ -890,16 +883,16 @@ static void read_branch_records(struct pmu_hw_events *cpuc,
static irqreturn_t armv8pmu_handle_irq(struct arm_pmu *cpu_pmu)
{
- u64 pmovsr;
struct perf_sample_data data;
struct pmu_hw_events *cpuc = this_cpu_ptr(cpu_pmu->hw_events);
struct pt_regs *regs;
+ u64 pmovsr;
int idx;
/*
- * Get and reset the IRQ flags
+ * Get the IRQ flags
*/
- pmovsr = armv8pmu_getreset_flags();
+ pmovsr = armv8pmu_getovf_flags();
/*
* Did an overflow occur?
@@ -907,6 +900,12 @@ static irqreturn_t armv8pmu_handle_irq(struct arm_pmu *cpu_pmu)
if (!armv8pmu_has_overflowed(pmovsr))
return IRQ_NONE;
+ /*
+ * Guest flag reset is handled by the kvm hook at the bottom of
+ * this function.
+ */
+ write_pmovsclr(pmovsr & ~kvm_pmu_guest_counter_mask());
+
/*
* Handle the counter(s) overflow(s)
*/
@@ -948,6 +947,9 @@ static irqreturn_t armv8pmu_handle_irq(struct arm_pmu *cpu_pmu)
*/
perf_event_overflow(event, &data, regs);
}
+
+ kvm_pmu_handle_guest_irq(pmovsr);
+
armv8pmu_start(cpu_pmu);
return IRQ_HANDLED;
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 0f2e39367d637..955f142a41b94 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -109,6 +109,9 @@ u64 kvm_pmu_guest_counter_mask(void);
void kvm_pmu_load(struct kvm_vcpu *vcpu);
void kvm_pmu_put(struct kvm_vcpu *vcpu);
void kvm_pmu_set_guest_owned(struct kvm_vcpu *vcpu);
+void kvm_pmu_handle_guest_irq(u64 pmovsr);
+bool kvm_pmu_host_start(void);
+bool kvm_pmu_host_stop(void);
void kvm_pmu_apply_single_event_filter(struct kvm_vcpu *vcpu, u8 idx);
#define kvm_pmu_get_access(vcpu) ((vcpu)->arch.pmu.access)
@@ -274,6 +277,9 @@ static inline u64 kvm_pmu_guest_counter_mask(void)
return 0;
}
+static inline void kvm_pmu_handle_guest_irq(u64 pmovsr) {}
+static inline bool kvm_pmu_host_start(void) { return false; }
+static inline bool kvm_pmu_host_stop(void) { return false; }
static inline void kvm_pmu_apply_single_event_filter(struct kvm_vcpu *vcpu, u8 idx) {}
static inline bool has_kvm_pmu_partition_support(void)
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 19/22] KVM: arm64: Detect overflows for the Partitioned PMU
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (17 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 18/22] perf: arm_pmuv3: Handle IRQs for Partitioned PMU guest counters Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 20/22] KVM: arm64: Add vCPU device attr to partition the PMU Colton Lewis
` (4 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
When re-entering the VM or synchronizing PMU state after a guest counter
overflow interrupt, evaluate whether any enabled and unmasked guest
counter has overflowed ((PMOVSSET_EL0 & PMINTENSET_EL1 & PMCNTENSET_EL0)
with PMCR_EL0.E set) and update the virtual PMU interrupt level in the
vGIC accordingly.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm64/kvm/pmu-direct.c | 55 +++++++++++++++++++++++++++++++++++++
arch/arm64/kvm/pmu-emul.c | 12 ++++++--
arch/arm64/kvm/pmu.c | 8 +++++-
include/kvm/arm_pmu.h | 2 ++
4 files changed, 73 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kvm/pmu-direct.c b/arch/arm64/kvm/pmu-direct.c
index 95b5a64052762..ec821aa54688f 100644
--- a/arch/arm64/kvm/pmu-direct.c
+++ b/arch/arm64/kvm/pmu-direct.c
@@ -534,6 +534,61 @@ void kvm_pmu_handle_guest_irq(u64 pmovsr)
for_each_set_bit(i, (unsigned long *)&govf, 64)
set_bit(i, (unsigned long *)__ctxt_sys_reg(&vcpu->arch.ctxt, PMOVSSET_EL0));
+
+ if (kvm_pmu_part_overflow_status(vcpu)) {
+ kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
+
+ if (!in_nmi())
+ kvm_vcpu_kick(vcpu);
+ else
+ irq_work_queue(&vcpu->arch.pmu.overflow_work);
+ }
+}
+
+/**
+ * kvm_pmu_part_overflow_status() - Determine if any guest counters have overflowed
+ * @vcpu: Pointer to struct kvm_vcpu
+ *
+ * Determine if any guest counters have overflowed and therefore an
+ * IRQ needs to be injected into the guest. If an overflow is detected
+ * while access is VCPU_PMU_ACCESS_FREE (for example, after state
+ * restoration via KVM_SET_ONE_REG), transition the vCPU to
+ * VCPU_PMU_ACCESS_GUEST_OWNED.
+ *
+ * Return: True if there was an overflow, false otherwise
+ */
+bool kvm_pmu_part_overflow_status(struct kvm_vcpu *vcpu)
+{
+ u64 mask = kvm_vcpu_pmu_guest_counter_mask(vcpu);
+ u64 pmovs, pmint, pmcr;
+ unsigned long flags;
+ bool overflow;
+
+ local_irq_save(flags);
+ if (vcpu->arch.pmu.loaded_on_cpu &&
+ vcpu == kvm_get_running_vcpu()) {
+ u64 hw_ovf = read_sysreg(pmovsset_el0) & mask;
+
+ if (hw_ovf) {
+ __vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, |=, hw_ovf);
+ write_sysreg(hw_ovf, pmovsclr_el0);
+ }
+ pmint = read_pmintenset();
+ pmcr = read_pmcr();
+ } else {
+ pmint = __vcpu_sys_reg(vcpu, PMINTENSET_EL1);
+ pmcr = __vcpu_sys_reg(vcpu, PMCR_EL0);
+ }
+
+ pmovs = __vcpu_sys_reg(vcpu, PMOVSSET_EL0);
+ local_irq_restore(flags);
+
+ overflow = (pmcr & ARMV8_PMU_PMCR_E) && (mask & pmovs & pmint);
+
+ if (overflow && kvm_pmu_get_access(vcpu) == VCPU_PMU_ACCESS_FREE)
+ kvm_pmu_set_guest_owned(vcpu);
+
+ return overflow;
}
/**
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index e8195984b0373..21e2c96abfdb1 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -268,7 +268,7 @@ void kvm_pmu_reprogram_counter_mask(struct kvm_vcpu *vcpu, u64 val)
* counter where the values of the global enable control, PMOVSSET_EL0[n], and
* PMINTENSET_EL1[n] are all 1.
*/
-bool kvm_pmu_overflow_status(struct kvm_vcpu *vcpu)
+bool kvm_pmu_emul_overflow_status(struct kvm_vcpu *vcpu)
{
u64 reg = __vcpu_sys_reg(vcpu, PMOVSSET_EL0);
@@ -296,8 +296,14 @@ bool kvm_pmu_should_notify_user(struct kvm_vcpu *vcpu)
{
struct kvm_sync_regs *sregs = &vcpu->run->s.regs;
bool run_level = sregs->device_irq_level & KVM_ARM_DEV_PMU;
+ bool overflow;
- return kvm_pmu_overflow_status(vcpu) != run_level;
+ if (kvm_pmu_is_partitioned(vcpu->kvm))
+ overflow = kvm_pmu_part_overflow_status(vcpu);
+ else
+ overflow = kvm_pmu_emul_overflow_status(vcpu);
+
+ return overflow != run_level;
}
/*
@@ -400,7 +406,7 @@ static void kvm_pmu_perf_overflow(struct perf_event *perf_event,
kvm_pmu_counter_increment(vcpu, BIT(idx + 1),
ARMV8_PMUV3_PERFCTR_CHAIN);
- if (kvm_pmu_overflow_status(vcpu)) {
+ if (kvm_pmu_emul_overflow_status(vcpu)) {
kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
if (!in_nmi())
diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c
index a8214ab52fcb5..4a3c6600b2678 100644
--- a/arch/arm64/kvm/pmu.c
+++ b/arch/arm64/kvm/pmu.c
@@ -409,12 +409,18 @@ u64 kvm_pmu_evtyper_mask(struct kvm *kvm)
static void kvm_pmu_update_state(struct kvm_vcpu *vcpu)
{
struct kvm_pmu *pmu = &vcpu->arch.pmu;
+ bool overflow;
if (unlikely(!irqchip_in_kernel(vcpu->kvm)))
return;
+ if (kvm_pmu_is_partitioned(vcpu->kvm))
+ overflow = kvm_pmu_part_overflow_status(vcpu);
+ else
+ overflow = kvm_pmu_emul_overflow_status(vcpu);
+
WARN_ON(kvm_vgic_inject_irq(vcpu->kvm, vcpu, pmu->irq_num,
- kvm_pmu_overflow_status(vcpu), pmu));
+ overflow, pmu));
}
/**
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 955f142a41b94..428a609eaf1a7 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -91,6 +91,8 @@ bool kvm_set_pmuserenr(u64 val);
void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu);
void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
void kvm_vcpu_pmu_resync_el0(void);
+bool kvm_pmu_emul_overflow_status(struct kvm_vcpu *vcpu);
+bool kvm_pmu_part_overflow_status(struct kvm_vcpu *vcpu);
#define kvm_vcpu_has_pmu(vcpu) \
(vcpu_has_feature(vcpu, KVM_ARM_VCPU_PMU_V3))
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 20/22] KVM: arm64: Add vCPU device attr to partition the PMU
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (18 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 19/22] KVM: arm64: Detect overflows for the Partitioned PMU Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-30 15:27 ` James Clark
2026-09-24 17:29 ` [PATCH v9 21/22] KVM: selftests: Add find_bit to KVM library Colton Lewis
` (3 subsequent siblings)
23 siblings, 1 reply; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
Add the KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION vCPU device attribute to
enable a Partitioned PMU for a VM where PMUv3 and VHE are supported.
When partitioning is enabled (tracked via
KVM_ARCH_FLAG_PARTITION_PMU_ENABLED), userspace must explicitly
configure the number of guest event counters via
KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS with a value strictly less than the
maximum number of general-purpose counters implemented by the PMU (or
0 only when FEAT_HPMN0 is supported), leaving at least one
general-purpose counter reserved for host profiling prior to calling
KVM_ARM_VCPU_PMU_V3_INIT.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
Documentation/virt/kvm/devices/vcpu.rst | 42 ++++++++++++++-
arch/arm64/include/asm/kvm_host.h | 1 +
arch/arm64/include/uapi/asm/kvm.h | 2 +
arch/arm64/kvm/pmu.c | 71 ++++++++++++++++++++++++-
arch/arm64/kvm/sys_regs.c | 5 +-
5 files changed, 118 insertions(+), 3 deletions(-)
diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt/kvm/devices/vcpu.rst
index deb5c51bc00c8..fb5921ed9dea2 100644
--- a/Documentation/virt/kvm/devices/vcpu.rst
+++ b/Documentation/virt/kvm/devices/vcpu.rst
@@ -57,6 +57,9 @@ Returns:
hardware PMU, or interrupt number not set (non-GICv5
guests, only)
-EBUSY PMUv3 already initialized
+ -EINVAL Partitioning enabled without explicitly configuring
+ fewer than max_counters via
+ KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS
======= ======================================================
Request the initialization of the PMUv3. If using the PMUv3 with an in-kernel
@@ -162,7 +165,8 @@ the cpu field to the processor id.
-EFAULT Error accessing the value pointed to by addr
-ENODEV PMUv3 not supported or GIC not initialized
-EINVAL No PMUv3 explicitly selected, or value of N out of
- range
+ range (or N >= max_counters when partitioning is
+ enabled)
======= ====================================================
Set the number of implemented event counters in the virtual PMU. This
@@ -172,6 +176,42 @@ explicitly selected, or the number of counters is out of range for the
selected PMU. Selecting a new PMU cancels the effect of setting this
attribute.
+1.6 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION
+---------------------------------------------------
+
+:Parameters: in kvm_device_attr.addr the address to an unsigned int (u32)
+ boolean value (non-zero to enable PMU partitioning, 0 to disable)
+
+:Returns:
+
+ ======= ========================================================
+ -EBUSY PMUv3 already initialized or a VCPU has already run
+ -EFAULT Error accessing the value pointed to by addr
+ -ENODEV KVM_ARM_VCPU_PMU_V3 feature missing from VCPU
+ -EPERM Host hardware or kernel configuration does not support
+ PMU partitioning (requires ARM64 VHE mode and PMUv3)
+ -EINVAL No PMUv3 associated with the VM, or
+ KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS was already set to
+ >= max_counters
+ -ENXIO Returned by KVM_HAS_DEVICE_ATTR when PMU partitioning is
+ unsupported on host hardware
+ ======= ========================================================
+
+Enable or disable hardware PMU partitioning for the VM. When enabled, physical
+PMUv3 hardware counters are partitioned between the guest and host using
+MDCR_EL2.HPMN (and FEAT_FGT fine-grained traps when supported by hardware).
+This grants the guest direct, untrapped EL0/EL1 hardware access to event
+counters 0..HPMN-1 and the cycle counter (PMCCNTR_EL0).
+
+When PMU partitioning is enabled, userspace must explicitly configure the
+number of guest event counters via KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS with a
+value strictly less than the maximum number of general-purpose counters
+implemented by the PMU (leaving at least one general-purpose counter reserved
+for host profiling) prior to calling KVM_ARM_VCPU_PMU_V3_INIT. Note that
+KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS configures general-purpose event counters
+(PMCR_EL0.N / MDCR_EL2.HPMN); the dedicated cycle counter (PMCCNTR_EL0) is
+unconditionally assigned to the guest partition when partitioning is enabled.
+
2. GROUP: KVM_ARM_VCPU_TIMER_CTRL
=================================
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 8dff576667d10..6180b977d8965 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -388,6 +388,7 @@ struct kvm_arch {
/* Maximum number of counters for the guest */
u8 nr_pmu_counters;
+ bool pmu_nr_counters_specified;
/* PMMIR_EL1.SLOTS value exposed to the guest. */
u8 pmmir_slots;
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 019e5e3d892e6..9d38090eb5e71 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -438,6 +438,8 @@ enum {
#define KVM_ARM_VCPU_PMU_V3_FILTER 2
#define KVM_ARM_VCPU_PMU_V3_SET_PMU 3
#define KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS 4
+#define KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION 5
+
#define KVM_ARM_VCPU_TIMER_CTRL 1
#define KVM_ARM_VCPU_TIMER_IRQ_VTIMER 0
#define KVM_ARM_VCPU_TIMER_IRQ_PTIMER 1
diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c
index 4a3c6600b2678..31e46a5e937c7 100644
--- a/arch/arm64/kvm/pmu.c
+++ b/arch/arm64/kvm/pmu.c
@@ -505,6 +505,14 @@ static int kvm_arm_pmu_v3_init(struct kvm_vcpu *vcpu)
return ret;
}
+ if (kvm_pmu_is_partitioned(vcpu->kvm)) {
+ unsigned int max_counters = kvm_arm_pmu_get_max_counters(vcpu->kvm);
+
+ if (!vcpu->kvm->arch.pmu_nr_counters_specified ||
+ vcpu->kvm->arch.nr_pmu_counters >= max_counters)
+ return -EINVAL;
+ }
+
init_irq_work(&vcpu->arch.pmu.overflow_work,
kvm_pmu_perf_overflow_notify_vcpu);
@@ -591,11 +599,25 @@ static void kvm_arm_set_nr_counters(struct kvm *kvm, unsigned int nr)
}
}
+static bool kvm_arm_pmu_any_vcpu_created(struct kvm *kvm)
+{
+ struct kvm_vcpu *vcpu;
+ unsigned long i;
+
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ if (vcpu->arch.pmu.created)
+ return true;
+ }
+
+ return false;
+}
+
static void kvm_arm_set_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu)
{
lockdep_assert_held(&kvm->arch.config_lock);
kvm->arch.arm_pmu = arm_pmu;
+ kvm->arch.pmu_nr_counters_specified = false;
kvm_arm_set_nr_counters(kvm, kvm_arm_pmu_get_max_counters(kvm));
}
@@ -642,6 +664,11 @@ static int kvm_arm_pmu_v3_set_pmu(struct kvm_vcpu *vcpu, int pmu_id)
break;
}
+ if (kvm_arm_pmu_any_vcpu_created(kvm)) {
+ ret = (kvm->arch.arm_pmu == arm_pmu) ? 0 : -EBUSY;
+ break;
+ }
+
kvm_arm_set_pmu(kvm, arm_pmu);
cpumask_copy(kvm->arch.supported_cpus, &arm_pmu->supported_cpus);
@@ -667,14 +694,26 @@ static int kvm_arm_pmu_v3_set_pmu(struct kvm_vcpu *vcpu, int pmu_id)
static int kvm_arm_pmu_v3_set_nr_counters(struct kvm_vcpu *vcpu, unsigned int n)
{
struct kvm *kvm = vcpu->kvm;
+ unsigned int max_counters;
+
+ if (kvm_vm_has_ran_once(kvm) ||
+ (kvm_arm_pmu_any_vcpu_created(kvm) &&
+ (!kvm->arch.pmu_nr_counters_specified ||
+ kvm->arch.nr_pmu_counters != n)))
+ return -EBUSY;
if (!kvm->arch.arm_pmu)
return -EINVAL;
- if (n > kvm_arm_pmu_get_max_counters(kvm))
+ max_counters = kvm_arm_pmu_get_max_counters(kvm);
+ if (n > max_counters)
+ return -EINVAL;
+
+ if (kvm_pmu_is_partitioned(kvm) && n >= max_counters)
return -EINVAL;
kvm_arm_set_nr_counters(kvm, n);
+ kvm->arch.pmu_nr_counters_specified = true;
return 0;
}
@@ -786,6 +825,31 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
return kvm_arm_pmu_v3_set_nr_counters(vcpu, n);
}
+ case KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION: {
+ unsigned int __user *uaddr = (unsigned int __user *)(long)attr->addr;
+ u32 val;
+
+ if (get_user(val, uaddr))
+ return -EFAULT;
+
+ if (!has_kvm_pmu_partition_support())
+ return -EPERM;
+
+ if (kvm_vm_has_ran_once(kvm) ||
+ (kvm_arm_pmu_any_vcpu_created(kvm) &&
+ kvm_pmu_is_partitioned(kvm) != !!val))
+ return -EBUSY;
+
+ if (!kvm->arch.arm_pmu)
+ return -EINVAL;
+
+ if (val && kvm->arch.pmu_nr_counters_specified &&
+ kvm->arch.nr_pmu_counters >= kvm_arm_pmu_get_max_counters(kvm))
+ return -EINVAL;
+
+ kvm_pmu_partition_enable(kvm, val);
+ return 0;
+ }
case KVM_ARM_VCPU_PMU_V3_INIT:
return kvm_arm_pmu_v3_init(vcpu);
}
@@ -827,6 +891,11 @@ int kvm_arm_pmu_v3_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
case KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS:
if (kvm_vcpu_has_pmu(vcpu))
return 0;
+ break;
+ case KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION:
+ if (kvm_vcpu_has_pmu(vcpu) && has_kvm_pmu_partition_support())
+ return 0;
+ break;
}
return -ENXIO;
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 20c46ef705d30..a4779593c4f8d 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1756,7 +1756,10 @@ static int set_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
if (!kvm_vm_has_ran_once(kvm) &&
!vcpu_has_nv(vcpu) &&
!kvm_vcpu_has_pmuv3_strict(vcpu) &&
- new_n <= kvm_arm_pmu_get_max_counters(kvm))
+ !kvm->arch.pmu_nr_counters_specified &&
+ new_n <= kvm_arm_pmu_get_max_counters(kvm) &&
+ (!kvm_pmu_is_partitioned(kvm) ||
+ new_n < kvm_arm_pmu_get_max_counters(kvm)))
kvm->arch.nr_pmu_counters = new_n;
mutex_unlock(&kvm->arch.config_lock);
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* Re: [PATCH v9 20/22] KVM: arm64: Add vCPU device attr to partition the PMU
2026-09-24 17:29 ` [PATCH v9 20/22] KVM: arm64: Add vCPU device attr to partition the PMU Colton Lewis
@ 2026-09-30 15:27 ` James Clark
2026-10-01 21:21 ` Colton Lewis
0 siblings, 1 reply; 31+ messages in thread
From: James Clark @ 2026-09-30 15:27 UTC (permalink / raw)
To: Colton Lewis
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel, kvm,
kvmarm, linux-arm-kernel
On 24/09/2026 18:29, Colton Lewis wrote:
> Add the KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION vCPU device attribute to
> enable a Partitioned PMU for a VM where PMUv3 and VHE are supported.
>
> When partitioning is enabled (tracked via
> KVM_ARCH_FLAG_PARTITION_PMU_ENABLED), userspace must explicitly
> configure the number of guest event counters via
> KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS with a value strictly less than the
> maximum number of general-purpose counters implemented by the PMU (or
> 0 only when FEAT_HPMN0 is supported), leaving at least one
> general-purpose counter reserved for host profiling prior to calling
> KVM_ARM_VCPU_PMU_V3_INIT.
>
> Signed-off-by: Colton Lewis <coltonlewis@google.com>
> ---
> Documentation/virt/kvm/devices/vcpu.rst | 42 ++++++++++++++-
> arch/arm64/include/asm/kvm_host.h | 1 +
> arch/arm64/include/uapi/asm/kvm.h | 2 +
> arch/arm64/kvm/pmu.c | 71 ++++++++++++++++++++++++-
> arch/arm64/kvm/sys_regs.c | 5 +-
> 5 files changed, 118 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt/kvm/devices/vcpu.rst
> index deb5c51bc00c8..fb5921ed9dea2 100644
> --- a/Documentation/virt/kvm/devices/vcpu.rst
> +++ b/Documentation/virt/kvm/devices/vcpu.rst
> @@ -57,6 +57,9 @@ Returns:
> hardware PMU, or interrupt number not set (non-GICv5
> guests, only)
> -EBUSY PMUv3 already initialized
> + -EINVAL Partitioning enabled without explicitly configuring
> + fewer than max_counters via
> + KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS
> ======= ======================================================
>
> Request the initialization of the PMUv3. If using the PMUv3 with an in-kernel
> @@ -162,7 +165,8 @@ the cpu field to the processor id.
> -EFAULT Error accessing the value pointed to by addr
> -ENODEV PMUv3 not supported or GIC not initialized
> -EINVAL No PMUv3 explicitly selected, or value of N out of
> - range
> + range (or N >= max_counters when partitioning is
> + enabled)
"No PMUv3 explicitly selected, or value of N > max_counters, or N >
max_counters - 1 when partitioning is enabled".
That might be clearer, otherwise it seems like max_counters being
relevant to "out of range" only applies to when partitioning is enabled,
not that it's max_counters all the time but one is -1.
^ permalink raw reply [flat|nested] 31+ messages in thread
* Re: [PATCH v9 20/22] KVM: arm64: Add vCPU device attr to partition the PMU
2026-09-30 15:27 ` James Clark
@ 2026-10-01 21:21 ` Colton Lewis
0 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-10-01 21:21 UTC (permalink / raw)
To: James Clark
Cc: Colton Lewis, Marc Zyngier, Oliver Upton, Oliver Upton,
Joey Gouly, Suzuki K Poulose, Zenghui Yu, Fuad Tabba,
Catalin Marinas, Will Deacon, Mark Rutland, Paolo Bonzini,
Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Robin Murphy, Zide Chen, Alexandru Elisei,
Ganapatrao Kulkarni, Mingwei Zhang, Jonathan Corbet,
Russell King, Shuah Khan, linux-perf-users, linux-kselftest,
linux-doc, linux-kernel, kvm, kvmarm, linux-arm-kernel
Hi James,
On Wed, Sep 30, 2026 at 04:27:27PM +0100, James Clark wrote:
> > @@ -77,7 +80,9 @@ Parameters: in:imaan address of a u32 value (N)
> > Returns:
> > ======= ====================================================
> > -EBUSY PMUv3 already initialized, or a vCPU has already run
> > - -EINVAL No PMUv3 explicitly selected, or value of N out of range
> > + -EINVAL No PMUv3 explicitly selected, or value of N out of
> > + range (>= max_counters when partitioning is
> > + enabled)
>
> "No PMUv3 explicitly selected, or value of N > max_counters, or N >
> max_counters - 1 when partitioning is enabled".
>
> That might be clearer, otherwise it seems like max_counters being relevant
> to "out of range" only applies to when partitioning is enabled, not that
> it's max_counters all the time but one is -1.
Agreed, that reads much better. I will update it to your phrasing in
v10.
Thanks,
Colton
^ permalink raw reply [flat|nested] 31+ messages in thread
* [PATCH v9 21/22] KVM: selftests: Add find_bit to KVM library
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (19 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 20/22] KVM: arm64: Add vCPU device attr to partition the PMU Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-24 17:29 ` [PATCH v9 22/22] KVM: arm64: selftests: Add test case for Partitioned PMU Colton Lewis
` (2 subsequent siblings)
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
Add lib/find_bit.c to the KVM selftests build using the same wrapper
pattern as lib/rbtree.c so selftests that depend on find_bit helpers
link cleanly when built standalone.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
tools/testing/selftests/kvm/Makefile.kvm | 1 +
tools/testing/selftests/kvm/lib/find_bit.c | 2 ++
2 files changed, 3 insertions(+)
create mode 100644 tools/testing/selftests/kvm/lib/find_bit.c
diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 96bab7002d39e..cfd1a4fe09ec4 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -5,6 +5,7 @@ all:
LIBKVM += lib/assert.c
LIBKVM += lib/elf.c
+LIBKVM += lib/find_bit.c
LIBKVM += lib/guest_modes.c
LIBKVM += lib/io.c
LIBKVM += lib/kvm_util.c
diff --git a/tools/testing/selftests/kvm/lib/find_bit.c b/tools/testing/selftests/kvm/lib/find_bit.c
new file mode 100644
index 0000000000000..5534248c663f7
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/find_bit.c
@@ -0,0 +1,2 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "../../../../lib/find_bit.c"
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* [PATCH v9 22/22] KVM: arm64: selftests: Add test case for Partitioned PMU
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (20 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 21/22] KVM: selftests: Add find_bit to KVM library Colton Lewis
@ 2026-09-24 17:29 ` Colton Lewis
2026-09-30 15:25 ` [PATCH v9 00/22] ARM64 PMU Partitioning James Clark
2026-09-30 15:26 ` James Clark
23 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-09-24 17:29 UTC (permalink / raw)
To: kvm, kvmarm, linux-arm-kernel
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, James Clark,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel,
Colton Lewis
Extend arm64/vpmu_counter_access to run all PMU counter access,
PMCR.N validation, and overflow interrupt tests against both the
emulated vPMU and the Partitioned PMU.
Introduce enum vpmu_impl (EMULATED_VPMU vs. PARTITIONED_VPMU) and thread
it through the test setup helpers to configure
KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION and
KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS when testing the Partitioned PMU.
Skip out-of-bounds counter access exception tests when the PMU is
partitioned, as hardware does not guarantee an UNDEFINED exception on
accesses to unimplemented counters.
Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
.../selftests/kvm/arm64/vpmu_counter_access.c | 129 ++++++++++++++----
1 file changed, 99 insertions(+), 30 deletions(-)
diff --git a/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c b/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
index 22223395969e0..811f8156cea3c 100644
--- a/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
+++ b/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c
@@ -25,12 +25,27 @@
/* The cycle counter bit position that's common among the PMU registers */
#define ARMV8_PMU_CYCLE_IDX 31
+enum pmu_impl {
+ EMULATED,
+ PARTITIONED
+};
+
+const char *pmu_impl_str[] = {
+ "Emulated",
+ "Partitioned"
+};
+
struct vpmu_vm {
struct kvm_vm *vm;
struct kvm_vcpu *vcpu;
};
+struct guest_context {
+ bool pmu_partitioned;
+};
+
static struct vpmu_vm vpmu_vm;
+static struct guest_context guest_context;
struct pmreg_sets {
u64 set_reg_id;
@@ -331,11 +346,16 @@ static void test_access_invalid_pmc_regs(struct pmc_accessor *acc, int pmc_idx)
/*
* Reading/writing the event count/type registers should cause
* an UNDEFINED exception.
+ *
+ * If the pmu is partitioned, we can't guarantee it because
+ * hardware doesn't.
*/
- TEST_EXCEPTION(ESR_ELx_EC_UNKNOWN, acc->read_cntr(pmc_idx));
- TEST_EXCEPTION(ESR_ELx_EC_UNKNOWN, acc->write_cntr(pmc_idx, 0));
- TEST_EXCEPTION(ESR_ELx_EC_UNKNOWN, acc->read_typer(pmc_idx));
- TEST_EXCEPTION(ESR_ELx_EC_UNKNOWN, acc->write_typer(pmc_idx, 0));
+ if (!guest_context.pmu_partitioned) {
+ TEST_EXCEPTION(ESR_ELx_EC_UNKNOWN, acc->read_cntr(pmc_idx));
+ TEST_EXCEPTION(ESR_ELx_EC_UNKNOWN, acc->write_cntr(pmc_idx, 0));
+ TEST_EXCEPTION(ESR_ELx_EC_UNKNOWN, acc->read_typer(pmc_idx));
+ TEST_EXCEPTION(ESR_ELx_EC_UNKNOWN, acc->write_typer(pmc_idx, 0));
+ }
/*
* The bit corresponding to the (unimplemented) counter in
* {PMCNTEN,PMINTEN,PMOVS}{SET,CLR} registers should be RAZ.
@@ -399,7 +419,7 @@ static void guest_code(u64 expected_pmcr_n)
}
/* Create a VM that has one vCPU with PMUv3 configured. */
-static void create_vpmu_vm(void *guest_code)
+static void create_vpmu_vm(void *guest_code, enum pmu_impl impl)
{
struct kvm_vcpu_init init;
u8 pmuver, ec;
@@ -409,6 +429,13 @@ static void create_vpmu_vm(void *guest_code)
.attr = KVM_ARM_VCPU_PMU_V3_IRQ,
.addr = (u64)&irq,
};
+ u32 partition = (impl == PARTITIONED);
+ struct kvm_device_attr part_attr = {
+ .group = KVM_ARM_VCPU_PMU_V3_CTRL,
+ .attr = KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION,
+ .addr = (uint64_t)&partition
+ };
+ int ret;
/* The test creates the vpmu_vm multiple times. Ensure a clean state */
memset(&vpmu_vm, 0, sizeof(vpmu_vm));
@@ -436,6 +463,15 @@ static void create_vpmu_vm(void *guest_code)
"Unexpected PMUVER (0x%x) on the vCPU with PMUv3", pmuver);
vcpu_ioctl(vpmu_vm.vcpu, KVM_SET_DEVICE_ATTR, &irq_attr);
+
+ ret = __vcpu_has_device_attr(
+ vpmu_vm.vcpu, KVM_ARM_VCPU_PMU_V3_CTRL, KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION);
+ if (!ret) {
+ vcpu_ioctl(vpmu_vm.vcpu, KVM_SET_DEVICE_ATTR, &part_attr);
+ guest_context.pmu_partitioned = partition;
+ pr_debug("Set PMU partitioning: %d\n", partition);
+ }
+
}
static void destroy_vpmu_vm(void)
@@ -461,13 +497,14 @@ static void run_vcpu(struct kvm_vcpu *vcpu, u64 pmcr_n)
}
}
-static void test_create_vpmu_vm_with_nr_counters(unsigned int nr_counters, bool expect_fail)
+static void test_create_vpmu_vm_with_nr_counters(
+ unsigned int nr_counters, enum pmu_impl impl, bool expect_fail)
{
struct kvm_vcpu *vcpu;
unsigned int prev;
int ret;
- create_vpmu_vm(guest_code);
+ create_vpmu_vm(guest_code, impl);
vcpu = vpmu_vm.vcpu;
prev = get_pmcr_n(vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0)));
@@ -475,21 +512,24 @@ static void test_create_vpmu_vm_with_nr_counters(unsigned int nr_counters, bool
ret = __vcpu_device_attr_set(vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS, &nr_counters);
- if (expect_fail)
+ if (expect_fail) {
TEST_ASSERT(ret && errno == EINVAL,
"Setting more PMU counters (%u) than available (%u) unexpectedly succeeded",
nr_counters, prev);
- else
- TEST_ASSERT(!ret, KVM_IOCTL_ERROR(KVM_SET_DEVICE_ATTR, ret));
+ return;
+ }
+
+ TEST_ASSERT(!ret, KVM_IOCTL_ERROR(KVM_SET_DEVICE_ATTR, ret));
vcpu_device_attr_set(vcpu, KVM_ARM_VCPU_PMU_V3_CTRL, KVM_ARM_VCPU_PMU_V3_INIT, NULL);
+ sync_global_to_guest(vpmu_vm.vm, guest_context);
}
/*
* Create a guest with one vCPU, set the PMCR_EL0.N for the vCPU to @pmcr_n,
* and run the test.
*/
-static void run_access_test(u64 pmcr_n)
+static void run_access_test(u64 pmcr_n, enum pmu_impl impl)
{
u64 sp;
struct kvm_vcpu *vcpu;
@@ -497,7 +537,7 @@ static void run_access_test(u64 pmcr_n)
pr_debug("Test with pmcr_n %lu\n", pmcr_n);
- test_create_vpmu_vm_with_nr_counters(pmcr_n, false);
+ test_create_vpmu_vm_with_nr_counters(pmcr_n, impl, false);
vcpu = vpmu_vm.vcpu;
/* Save the initial sp to restore them later to run the guest again */
@@ -531,14 +571,14 @@ static struct pmreg_sets validity_check_reg_sets[] = {
* Create a VM, and check if KVM handles the userspace accesses of
* the PMU register sets in @validity_check_reg_sets[] correctly.
*/
-static void run_pmregs_validity_test(u64 pmcr_n)
+static void run_pmregs_validity_test(u64 pmcr_n, enum pmu_impl impl)
{
int i;
struct kvm_vcpu *vcpu;
u64 set_reg_id, clr_reg_id, reg_val;
u64 valid_counters_mask, max_counters_mask;
- test_create_vpmu_vm_with_nr_counters(pmcr_n, false);
+ test_create_vpmu_vm_with_nr_counters(pmcr_n, impl, false);
vcpu = vpmu_vm.vcpu;
valid_counters_mask = get_counters_mask(pmcr_n);
@@ -588,11 +628,11 @@ static void run_pmregs_validity_test(u64 pmcr_n)
* the vCPU to @pmcr_n, which is larger than the host value.
* The attempt should fail as @pmcr_n is too big to set for the vCPU.
*/
-static void run_error_test(u64 pmcr_n)
+static void run_error_test(u64 pmcr_n, enum pmu_impl impl)
{
- pr_debug("Error test with pmcr_n %lu (larger than the host)\n", pmcr_n);
+ pr_debug("Error test with pmcr_n %lu (larger than the host allows)\n", pmcr_n);
- test_create_vpmu_vm_with_nr_counters(pmcr_n, true);
+ test_create_vpmu_vm_with_nr_counters(pmcr_n, impl, true);
destroy_vpmu_vm();
}
@@ -600,21 +640,26 @@ static void run_error_test(u64 pmcr_n)
* Return the default number of implemented PMU event counters excluding
* the cycle counter (i.e. PMCR_EL0.N value) for the guest.
*/
-static u64 get_pmcr_n_limit(void)
+static u64 get_pmcr_n_limit(enum pmu_impl impl)
{
- u64 pmcr;
+ u64 pmcr, n;
- create_vpmu_vm(guest_code);
+ create_vpmu_vm(guest_code, impl);
pmcr = vcpu_get_reg(vpmu_vm.vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0));
destroy_vpmu_vm();
- return get_pmcr_n(pmcr);
+
+ n = get_pmcr_n(pmcr);
+ if (impl == PARTITIONED && n > 0)
+ return n - 1;
+
+ return n;
}
static bool kvm_supports_nr_counters_attr(void)
{
bool supported;
- create_vpmu_vm(NULL);
+ create_vpmu_vm(NULL, EMULATED);
supported = !__vcpu_has_device_attr(vpmu_vm.vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS);
destroy_vpmu_vm();
@@ -622,22 +667,46 @@ static bool kvm_supports_nr_counters_attr(void)
return supported;
}
-int main(void)
+static bool kvm_supports_partition_attr(void)
+{
+ bool supported;
+
+ create_vpmu_vm(NULL, EMULATED);
+ supported = !__vcpu_has_device_attr(vpmu_vm.vcpu, KVM_ARM_VCPU_PMU_V3_CTRL,
+ KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION);
+ destroy_vpmu_vm();
+
+ return supported;
+}
+
+void test_pmu(enum pmu_impl impl)
{
u64 i, pmcr_n;
- TEST_REQUIRE(kvm_has_cap(KVM_CAP_ARM_PMU_V3));
- TEST_REQUIRE(kvm_supports_vgic_v3());
- TEST_REQUIRE(kvm_supports_nr_counters_attr());
+ pr_info("Testing PMU: Implementation = %s\n", pmu_impl_str[impl]);
+
+ pmcr_n = get_pmcr_n_limit(impl);
+ pr_debug("PMCR_EL0.N: Limit = %lu\n", pmcr_n);
- pmcr_n = get_pmcr_n_limit();
for (i = 0; i <= pmcr_n; i++) {
- run_access_test(i);
- run_pmregs_validity_test(i);
+ run_access_test(i, impl);
+ run_pmregs_validity_test(i, impl);
}
for (i = pmcr_n + 1; i < ARMV8_PMU_MAX_COUNTERS; i++)
- run_error_test(i);
+ run_error_test(i, impl);
+}
+
+int main(void)
+{
+ TEST_REQUIRE(kvm_has_cap(KVM_CAP_ARM_PMU_V3));
+ TEST_REQUIRE(kvm_supports_vgic_v3());
+ TEST_REQUIRE(kvm_supports_nr_counters_attr());
+
+ test_pmu(EMULATED);
+
+ if (kvm_supports_partition_attr() && get_pmcr_n_limit(EMULATED) > 0)
+ test_pmu(PARTITIONED);
return 0;
}
--
2.56.0.rc1.310.g51773c2048-goog
^ permalink raw reply [flat|nested] 31+ messages in thread* Re: [PATCH v9 00/22] ARM64 PMU Partitioning
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (21 preceding siblings ...)
2026-09-24 17:29 ` [PATCH v9 22/22] KVM: arm64: selftests: Add test case for Partitioned PMU Colton Lewis
@ 2026-09-30 15:25 ` James Clark
2026-10-01 21:33 ` Colton Lewis
2026-09-30 15:26 ` James Clark
23 siblings, 1 reply; 31+ messages in thread
From: James Clark @ 2026-09-30 15:25 UTC (permalink / raw)
To: Colton Lewis
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel, kvm,
kvmarm, linux-arm-kernel
On 24/09/2026 18:29, Colton Lewis wrote:
> This series creates a new PMU scheme on ARM, a partitioned PMU that
> allows reserving a subset of counters for more direct guest access,
> significantly reducing overhead. More details, including performance
> benchmarks, can be read in the v1 cover letter linked below.
>
> There is no longer a kernel command line parameter
> (`arm_pmuv3.reserved_host_counters`); PMU partitioning is now completely
> controlled via the KVM API using `KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION`
> and `KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS` vCPU device attributes. When
> partitioning is enabled for a VM, userspace must explicitly configure a
> guest event counter count strictly less than the maximum general-purpose
> counters implemented by the PMU (leaving at least one general-purpose
> counter for the host) prior to calling `KVM_ARM_VCPU_PMU_V3_INIT`. A QEMU
> patch demonstrating how to use the uAPI is sent separately.
>
> An overview of what this series accomplishes was presented at KVM
> Forum 2025. Slides [1] and video [2] are linked below.
>
> v9:
>
> * Rebase on top of v7.3-rc4.
>
> * Drop the `arm_pmuv3.reserved_host_counters` module parameter so
> partitioning is completely controlled via the KVM vCPU device
> attribute uAPI (`KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION` and
> `KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS`), and document the new
> attribute and counter allocation rules in
> `Documentation/virt/kvm/devices/vcpu.rst` (James Clark).
>
> * Move the dynamic counter allocation mask (`cntr_mask`) from global
> `struct arm_pmu` to per-CPU `struct pmu_hw_events` (`cpuc->cntr_mask`)
> in a dedicated `drivers/perf` patch, fixing multi-pCPU counter
> reservation clobbering on vCPU migration and eliminating the
> `cpu_pm_pmu_setup()` cpuidle `WARN_ON_ONCE` (Zide Chen, James Clark).
>
> * Synchronously propagate trapped guest writes to `PMEVTYPER<n>_EL0`
> and `PMCCFILTR_EL0` to hardware via `kvm_pmu_apply_single_event_filter()`
> when guest-owned, fixing in-guest `perf stat` event count skew across
> runs (James Clark, Sashiko AI Review).
>
> * Refactor `armv8pmu_can_use_pmccntr()` and `armv8pmu_get_event_idx()`
> to check `cntr_mask` inside `armv8pmu_can_use_pmccntr()` and un-nest
> the 64-bit user-access check so cycle events fall back cleanly to
> general-purpose counters when `PMCCNTR_EL0` is reserved by a guest
> (Robin Murphy).
>
> * Restrict the lazy transition to `VCPU_PMU_ACCESS_GUEST_OWNED` to when
> the guest actively enables counting (`PMCR_EL0.E = 1` or setting guest
> counter bits in `PMCNTENSET_EL0` / `PMINTENSET_EL1`), preventing guest
> boot-time PMU probing from prematurely claiming hardware counters and
> triggering spurious host counter preemption warnings (James Clark).
>
> * Fix patch dependency ordering and series bisectability across all
> commits, removing intermediate `max_guest_counters` / `hw_cntr_impl`
> churn and squashing the selftest exception relaxation into the
> Partitioned PMU selftest patch (James Clark).
>
> * Fix compiler warning for `struct arm_pmu` declaration in
> `include/kvm/arm_pmu.h` (kernel test robot) and guard
> `kvm_pmu_host_counter_mask()` when KVM is compiled in but not active
> (wuyifan).
>
> * Track physical CPU PMU residency in `vcpu->arch.pmu.loaded_on_cpu`
> separately from `VCPU_PMU_ACCESS_GUEST_OWNED`, and toggle
> `MDCR_EL2.HPME` via `kvm_pmu_host_start()` / `kvm_pmu_host_stop()`
> instead of `PMCR_EL0.E` when starting/stopping host perf events while
> a partitioned guest is loaded.
>
> * Allow `kvm_vcpu_pmu_resync_el0()` to resynchronize VHE EL0 event
> filters (`PMEVTYPER<n>_EL0.U`) in process context and order
> `kvm_pmu_put()` before `kvm_vcpu_pmu_restore_host()` in
> `kvm_arch_vcpu_put()`.
>
> * Address additional Sashiko AI Review findings:
> - Check `idx - 1` against `cpuc->cntr_mask` in `armv8pmu_get_chain_idx()`
> to prevent 64-bit chained host events from crossing an odd `HPMN`
> partition boundary, and use `cpuc->cntr_mask` in
> `armv8pmu_enable_user_access()`.
> - Latch live hardware `PMOVSSET_EL0` overflow bits for guest counters
> with IRQs disabled (`local_irq_save()`) in `kvm_pmu_part_overflow_status()`
> and during trapped guest accesses to `PMOVS{SET,CLR}_EL0`.
> - Add mandatory `isb()` barriers after control-plane system register
> writes (`mdcr_el2`, `pmcntenclr_el0`, `pmintenclr_el1`), preserve
> guest `PMSELR_EL0` / `PMUSERENR_EL0` when `MDCR_EL2.TPM == 0`, and
> restore host `PMCR_EL0` control flags on `kvm_pmu_put()`.
>
> v8:
> https://lore.kernel.org/kvmarm/20260612192909.1153907-1-coltonlewis@google.com/
>
> v7:
> https://lore.kernel.org/kvmarm/20260504211813.1804997-1-coltonlewis@google.com/
>
> v6:
> https://lore.kernel.org/kvmarm/20260209221414.2169465-1-coltonlewis@google.com/
>
> v5:
> https://lore.kernel.org/kvmarm/20251209205121.1871534-1-coltonlewis@google.com/
>
> v4:
> https://lore.kernel.org/kvmarm/20250714225917.1396543-1-coltonlewis@google.com/
>
> v3:
> https://lore.kernel.org/kvm/20250626200459.1153955-1-coltonlewis@google.com/
>
> v2:
> https://lore.kernel.org/kvm/20250620221326.1261128-1-coltonlewis@google.com/
>
> v1:
> https://lore.kernel.org/kvm/20250602192702.2125115-1-coltonlewis@google.com/
>
> [1] https://gitlab.com/qemu-project/kvm-forum/-/raw/main/_attachments/2025/Optimizing__itvHkhc.pdf
> [2] https://www.youtube.com/watch?v=YRzZ8jMIA6M&list=PLW3ep1uCIRfxwmllXTOA2txfDWN6vUOHp&index=9
>
> Colton Lewis (21):
> arm64: cpufeature: Add cpucap for HPMN0
> KVM: arm64: Reorganize PMU functions
> perf: arm_pmuv3: Generalize counter bitmasks
> perf: arm_pmuv3: Move counter allocation mask to per-CPU struct
> pmu_hw_events
> perf: arm_pmuv3: Check cntr_mask before using pmccntr
> perf: arm_pmuv3: Allocate counter indices from high to low
> KVM: arm64: Add initial scaffolding for Partitioned PMU
> KVM: arm64: Set up FGT for Partitioned PMU
> KVM: arm64: Add Partitioned PMU register trap handlers
> KVM: arm64: Set up MDCR_EL2 to handle a Partitioned PMU
> KVM: arm64: Context swap Partitioned PMU guest registers
> KVM: arm64: Enforce PMU event filter at vcpu_load()
> perf: Add perf_pmu_resched_update()
> KVM: arm64: Allow kvm_vcpu_pmu_resync_el0() to resync filters in
> process context
> KVM: arm64: Apply dynamic guest counter reservations
> KVM: arm64: Implement lazy PMU context swaps
> perf: arm_pmuv3: Handle IRQs for Partitioned PMU guest counters
> KVM: arm64: Detect overflows for the Partitioned PMU
> KVM: arm64: Add vCPU device attr to partition the PMU
> KVM: selftests: Add find_bit to KVM library
> KVM: arm64: selftests: Add test case for Partitioned PMU
>
> Marc Zyngier (1):
> KVM: arm64: Reorganize PMU includes
>
> Documentation/virt/kvm/devices/vcpu.rst | 42 +-
> arch/arm/include/asm/arm_pmuv3.h | 16 +
> arch/arm64/include/asm/arm_pmuv3.h | 7 +-
> arch/arm64/include/asm/kvm_host.h | 18 +-
> arch/arm64/include/asm/kvm_types.h | 6 +-
> arch/arm64/include/uapi/asm/kvm.h | 2 +
> arch/arm64/kernel/cpufeature.c | 10 +-
> arch/arm64/kvm/Makefile | 2 +-
> arch/arm64/kvm/arm.c | 4 +-
> arch/arm64/kvm/config.c | 49 +-
> arch/arm64/kvm/debug.c | 41 +-
> arch/arm64/kvm/pmu-direct.c | 636 ++++++++++++++
> arch/arm64/kvm/pmu-emul.c | 718 +---------------
> arch/arm64/kvm/pmu.c | 787 +++++++++++++++++-
> arch/arm64/kvm/sys_regs.c | 334 ++++++--
> arch/arm64/tools/cpucaps | 1 +
> arch/arm64/tools/sysreg | 6 +-
> drivers/perf/arm_pmu.c | 7 +-
> drivers/perf/arm_pmuv3.c | 97 ++-
> include/kvm/arm_pmu.h | 93 ++-
> include/linux/perf/arm_pmu.h | 2 +
> include/linux/perf/arm_pmuv3.h | 14 +-
> include/linux/perf_event.h | 3 +
> kernel/events/core.c | 31 +-
> tools/include/perf/arm_pmuv3.h | 12 +-
> tools/testing/selftests/kvm/Makefile.kvm | 1 +
> .../selftests/kvm/arm64/vpmu_counter_access.c | 129 ++-
> tools/testing/selftests/kvm/lib/find_bit.c | 2 +
> 28 files changed, 2200 insertions(+), 870 deletions(-)
> create mode 100644 arch/arm64/kvm/pmu-direct.c
> create mode 100644 tools/testing/selftests/kvm/lib/find_bit.c
>
>
> base-commit: 93f51579e7df248780214094418f205253383cc5
Hi Colton,
Looks good to me, everything seems to be working now:
Tested-by: James Clark <james.clark@linaro.org>
There are still a few Sashiko comments though, and one critical one
about racing with pseudo-NMI PMU interrupts that looked reasonable. I
tried to test it and reproduce an actual issue but couldn't, so maybe
it's bogus.
^ permalink raw reply [flat|nested] 31+ messages in thread* Re: [PATCH v9 00/22] ARM64 PMU Partitioning
2026-09-30 15:25 ` [PATCH v9 00/22] ARM64 PMU Partitioning James Clark
@ 2026-10-01 21:33 ` Colton Lewis
0 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-10-01 21:33 UTC (permalink / raw)
To: James Clark
Cc: Colton Lewis, Marc Zyngier, Oliver Upton, Oliver Upton,
Joey Gouly, Suzuki K Poulose, Zenghui Yu, Fuad Tabba,
Catalin Marinas, Will Deacon, Mark Rutland, Paolo Bonzini,
Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Robin Murphy, Zide Chen, Alexandru Elisei,
Ganapatrao Kulkarni, Mingwei Zhang, Jonathan Corbet,
Russell King, Shuah Khan, linux-perf-users, linux-kselftest,
linux-doc, linux-kernel, kvm, kvmarm, linux-arm-kernel
Hi James,
On Wed, Sep 30, 2026 at 04:25:36PM +0100, James Clark wrote:
> Looks good to me, everything seems to be working now:
>
> Tested-by: James Clark <james.clark@linaro.org>
Thank you for testing and for all the reviews!
> There are still a few Sashiko comments though, and one critical one about
> racing with pseudo-NMI PMU interrupts that looked reasonable. I tried to
> test it and reproduce an actual issue but couldn't, so maybe it's bogus.
The "Critical" Sashiko comment on Patch 19/22 (claiming that clearing
hardware PMOVSSET_EL0 loses overflow bits because the guest has direct
untrapped access to PMOVSSET_EL0) is a false positive: Patch 09/22 sets
HDFGRTR_EL2_PMOVS and HDFGWTR_EL2_PMOVS (and without FGT, MDCR_EL2.TPM
is set), so guest accesses to PMOVSSET_EL0 and PMOVSCLR_EL0 always trap
to pmu_reg_read() / pmu_reg_write().
The pseudo-NMI race comments on Patch 11/22 and Patch 19/22 are
theoretically possible in a narrow 2-instruction RMW window because
local_irq_save() does not mask GICv3 pseudo-NMIs, which explains why it
wasn't reproducible in practice. In v10 I will make the PMOVSSET_EL0
shadow updates and vcpu->arch.mdcr_el2 assignment atomic, and address
the other valid Sashiko findings.
Thanks,
Colton
^ permalink raw reply [flat|nested] 31+ messages in thread
* Re: [PATCH v9 00/22] ARM64 PMU Partitioning
2026-09-24 17:29 [PATCH v9 00/22] ARM64 PMU Partitioning Colton Lewis
` (22 preceding siblings ...)
2026-09-30 15:25 ` [PATCH v9 00/22] ARM64 PMU Partitioning James Clark
@ 2026-09-30 15:26 ` James Clark
2026-10-01 21:33 ` Colton Lewis
23 siblings, 1 reply; 31+ messages in thread
From: James Clark @ 2026-09-30 15:26 UTC (permalink / raw)
To: Colton Lewis
Cc: Marc Zyngier, Oliver Upton, Oliver Upton, Joey Gouly,
Suzuki K Poulose, Zenghui Yu, Fuad Tabba, Catalin Marinas,
Will Deacon, Mark Rutland, Paolo Bonzini, Peter Zijlstra,
Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim,
Robin Murphy, Zide Chen, Alexandru Elisei, Ganapatrao Kulkarni,
Mingwei Zhang, Jonathan Corbet, Russell King, Shuah Khan,
linux-perf-users, linux-kselftest, linux-doc, linux-kernel, kvm,
kvmarm, linux-arm-kernel
On 24/09/2026 18:29, Colton Lewis wrote:
> This series creates a new PMU scheme on ARM, a partitioned PMU that
> allows reserving a subset of counters for more direct guest access,
> significantly reducing overhead. More details, including performance
> benchmarks, can be read in the v1 cover letter linked below.
>
> There is no longer a kernel command line parameter
> (`arm_pmuv3.reserved_host_counters`); PMU partitioning is now completely
> controlled via the KVM API using `KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION`
> and `KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS` vCPU device attributes. When
As far as I know there isn't a straightforward way to get the number of
hw counters from userspace. You have to either parse dmesg or attempt to
open incrementally more counters in a group until it fails.
This makes doing things like "use all counters for guest" or "reserve
two for the host" difficult. Maybe it's time to add a file to the PMU
that userspace can use query this.
^ permalink raw reply [flat|nested] 31+ messages in thread* Re: [PATCH v9 00/22] ARM64 PMU Partitioning
2026-09-30 15:26 ` James Clark
@ 2026-10-01 21:33 ` Colton Lewis
0 siblings, 0 replies; 31+ messages in thread
From: Colton Lewis @ 2026-10-01 21:33 UTC (permalink / raw)
To: James Clark
Cc: Colton Lewis, Marc Zyngier, Oliver Upton, Oliver Upton,
Joey Gouly, Suzuki K Poulose, Zenghui Yu, Fuad Tabba,
Catalin Marinas, Will Deacon, Mark Rutland, Paolo Bonzini,
Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Robin Murphy, Zide Chen, Alexandru Elisei,
Ganapatrao Kulkarni, Mingwei Zhang, Jonathan Corbet,
Russell King, Shuah Khan, linux-perf-users, linux-kselftest,
linux-doc, linux-kernel, kvm, kvmarm, linux-arm-kernel
Hi James,
On Wed, Sep 30, 2026 at 04:26:23PM +0100, James Clark wrote:
> On 24/09/2026 18:29, Colton Lewis wrote:
> > This series creates a new PMU scheme on ARM, a partitioned PMU that
> > allows reserving a subset of counters for more direct guest access,
> > significantly reducing overhead. More details, including performance
> > benchmarks, can be read in the v1 cover letter linked below.
> >
> > There is no longer a kernel command line parameter
> > (`arm_pmuv3.reserved_host_counters`); PMU partitioning is now completely
> > controlled via the KVM API using `KVM_ARM_VCPU_PMU_V3_ENABLE_PARTITION`
> > and `KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS` vCPU device attributes. When
>
> As far as I know there isn't a straightforward way to get the number of hw
> counters from userspace. You have to either parse dmesg or attempt to open
> incrementally more counters in a group until it fails.
>
> This makes doing things like "use all counters for guest" or "reserve two
> for the host" difficult. Maybe it's time to add a file to the PMU that
> userspace can use query this.
Inside a VMM, userspace can query the default PMCR_EL0.N via
KVM_GET_ONE_REG(SYS_PMCR_EL0) after KVM_ARM_VCPU_INIT (or
KVM_ARM_VCPU_PMU_V3_SET_PMU) and before calling
KVM_ARM_VCPU_PMU_V3_SET_NR_COUNTERS, since KVM initializes
nr_pmu_counters to the PMU's max_counters (which is how
vpmu_counter_access discovers the limit).
For users and management tools outside the VMM (e.g. choosing N to pass
on the QEMU command line), I agree it's awkward that
/sys/bus/event_source/devices/<pmu>/caps/ exposes slots and bus_width
but not the number of counters. I will add a patch to expose a caps
attribute for the number of counters in drivers/perf/arm_pmuv3.c.
Thanks,
Colton
^ permalink raw reply [flat|nested] 31+ messages in thread