[PATCH v10 08/10] KVM: arm64: coresight: Give TRBE enabled state to KVM

[James Clark <james.clark@linaro.org>]

Currently in nVHE, KVM has to check if TRBE is enabled on every guest
switch even if it was never used. Because it's a debug feature and is
more likely to not be used than used, give KVM the TRBE buffer status to
allow a much simpler and faster do-nothing path in the hyp.

Protected mode now disables trace regardless of TRBE (because
trfcr_while_in_guest is always 0), which was not previously done.
However, it continues to flush whenever the buffer is enabled
regardless of the filter status. This avoids the hypothetical case of a
host that had disabled the filter but not flushed which would arise if
only doing the flush when the filter was enabled.

Signed-off-by: James Clark <james.clark@linaro.org>
---
 arch/arm64/include/asm/kvm_host.h            |  9 +++
 arch/arm64/kvm/debug.c                       | 32 +++++++++-
 arch/arm64/kvm/hyp/nvhe/debug-sr.c           | 63 ++++++++++++--------
 drivers/hwtracing/coresight/coresight-trbe.c |  3 +
 4 files changed, 79 insertions(+), 28 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index fb252d540850..b244ec44bd3a 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -612,6 +612,8 @@ struct cpu_sve_state {
 struct kvm_host_data {
 #define KVM_HOST_DATA_FLAG_HAS_SPE	0
 #define KVM_HOST_DATA_FLAG_HAS_TRBE	1
+#define KVM_HOST_DATA_FLAG_TRBE_ENABLED			2
+#define KVM_HOST_DATA_FLAG_EL1_TRACING_CONFIGURED	3
 	unsigned long flags;
 
 	struct kvm_cpu_context host_ctxt;
@@ -657,6 +659,9 @@ struct kvm_host_data {
 		u64 mdcr_el2;
 	} host_debug_state;
 
+	/* Guest trace filter value */
+	u64 trfcr_while_in_guest;
+
 	/* Number of programmable event counters (PMCR_EL0.N) for this CPU */
 	unsigned int nr_event_counters;
 };
@@ -1381,6 +1386,8 @@ static inline bool kvm_pmu_counter_deferred(struct perf_event_attr *attr)
 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);
 #else
 static inline void kvm_set_pmu_events(u64 set, struct perf_event_attr *attr) {}
 static inline void kvm_clr_pmu_events(u64 clr) {}
@@ -1388,6 +1395,8 @@ static inline bool kvm_set_pmuserenr(u64 val)
 {
 	return false;
 }
+static inline void kvm_enable_trbe(void) {}
+static inline void kvm_disable_trbe(void) {}
 #endif
 
 void kvm_vcpu_load_vhe(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index 1ee2fd765b62..e1ac3d2a65be 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -309,7 +309,33 @@ void kvm_init_host_debug_data(void)
 	    !(read_sysreg_s(SYS_PMBIDR_EL1) & PMBIDR_EL1_P))
 		host_data_set_flag(HAS_SPE);
 
-	if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_TraceBuffer_SHIFT) &&
-	    !(read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_EL1_P))
-		host_data_set_flag(HAS_TRBE);
+	if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_TraceFilt_SHIFT)) {
+		/* Force disable trace in protected mode in case of no TRBE */
+		if (is_protected_kvm_enabled())
+			host_data_set_flag(EL1_TRACING_CONFIGURED);
+
+		if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_TraceBuffer_SHIFT) &&
+		    !(read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_EL1_P))
+			host_data_set_flag(HAS_TRBE);
+	}
+}
+
+void kvm_enable_trbe(void)
+{
+	if (has_vhe() || is_protected_kvm_enabled() ||
+	    WARN_ON_ONCE(preemptible()))
+		return;
+
+	host_data_set_flag(TRBE_ENABLED);
+}
+EXPORT_SYMBOL_GPL(kvm_enable_trbe);
+
+void kvm_disable_trbe(void)
+{
+	if (has_vhe() || is_protected_kvm_enabled() ||
+	    WARN_ON_ONCE(preemptible()))
+		return;
+
+	host_data_clear_flag(TRBE_ENABLED);
 }
+EXPORT_SYMBOL_GPL(kvm_disable_trbe);
diff --git a/arch/arm64/kvm/hyp/nvhe/debug-sr.c b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
index 858bb38e273f..2f4a4f5036bb 100644
--- a/arch/arm64/kvm/hyp/nvhe/debug-sr.c
+++ b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
@@ -51,32 +51,45 @@ static void __debug_restore_spe(u64 pmscr_el1)
 	write_sysreg_el1(pmscr_el1, SYS_PMSCR);
 }
 
-static void __debug_save_trace(u64 *trfcr_el1)
+static void __trace_do_switch(u64 *saved_trfcr, u64 new_trfcr)
 {
-	*trfcr_el1 = 0;
+	*saved_trfcr = read_sysreg_el1(SYS_TRFCR);
+	write_sysreg_el1(new_trfcr, SYS_TRFCR);
+}
 
-	/* Check if the TRBE is enabled */
-	if (!(read_sysreg_s(SYS_TRBLIMITR_EL1) & TRBLIMITR_EL1_E))
-		return;
-	/*
-	 * Prohibit trace generation while we are in guest.
-	 * Since access to TRFCR_EL1 is trapped, the guest can't
-	 * modify the filtering set by the host.
-	 */
-	*trfcr_el1 = read_sysreg_el1(SYS_TRFCR);
-	write_sysreg_el1(0, SYS_TRFCR);
-	isb();
-	/* Drain the trace buffer to memory */
-	tsb_csync();
+static bool __trace_needs_drain(void)
+{
+	if (is_protected_kvm_enabled() && host_data_test_flag(HAS_TRBE))
+		return read_sysreg_s(SYS_TRBLIMITR_EL1) & TRBLIMITR_EL1_E;
+
+	return host_data_test_flag(TRBE_ENABLED);
 }
 
-static void __debug_restore_trace(u64 trfcr_el1)
+static bool __trace_needs_switch(void)
 {
-	if (!trfcr_el1)
-		return;
+	return host_data_test_flag(TRBE_ENABLED) ||
+	       host_data_test_flag(EL1_TRACING_CONFIGURED);
+}
+
+static void __trace_switch_to_guest(void)
+{
+	/* Unsupported with TRBE so disable */
+	if (host_data_test_flag(TRBE_ENABLED))
+		*host_data_ptr(trfcr_while_in_guest) = 0;
+
+	__trace_do_switch(host_data_ptr(host_debug_state.trfcr_el1),
+			  *host_data_ptr(trfcr_while_in_guest));
 
-	/* Restore trace filter controls */
-	write_sysreg_el1(trfcr_el1, SYS_TRFCR);
+	if (__trace_needs_drain()) {
+		isb();
+		tsb_csync();
+	}
+}
+
+static void __trace_switch_to_host(void)
+{
+	__trace_do_switch(host_data_ptr(trfcr_while_in_guest),
+			  *host_data_ptr(host_debug_state.trfcr_el1));
 }
 
 void __debug_save_host_buffers_nvhe(struct kvm_vcpu *vcpu)
@@ -84,9 +97,9 @@ void __debug_save_host_buffers_nvhe(struct kvm_vcpu *vcpu)
 	/* Disable and flush SPE data generation */
 	if (host_data_test_flag(HAS_SPE))
 		__debug_save_spe(host_data_ptr(host_debug_state.pmscr_el1));
-	/* Disable and flush Self-Hosted Trace generation */
-	if (host_data_test_flag(HAS_TRBE))
-		__debug_save_trace(host_data_ptr(host_debug_state.trfcr_el1));
+
+	if (__trace_needs_switch())
+		__trace_switch_to_guest();
 }
 
 void __debug_switch_to_guest(struct kvm_vcpu *vcpu)
@@ -98,8 +111,8 @@ void __debug_restore_host_buffers_nvhe(struct kvm_vcpu *vcpu)
 {
 	if (host_data_test_flag(HAS_SPE))
 		__debug_restore_spe(*host_data_ptr(host_debug_state.pmscr_el1));
-	if (host_data_test_flag(HAS_TRBE))
-		__debug_restore_trace(*host_data_ptr(host_debug_state.trfcr_el1));
+	if (__trace_needs_switch())
+		__trace_switch_to_host();
 }
 
 void __debug_switch_to_host(struct kvm_vcpu *vcpu)
diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
index 03d3695ba5aa..a728802d2206 100644
--- a/drivers/hwtracing/coresight/coresight-trbe.c
+++ b/drivers/hwtracing/coresight/coresight-trbe.c
@@ -17,6 +17,7 @@
 
 #include <asm/barrier.h>
 #include <asm/cpufeature.h>
+#include <linux/kvm_host.h>
 #include <linux/vmalloc.h>
 
 #include "coresight-self-hosted-trace.h"
@@ -221,6 +222,7 @@ static inline void set_trbe_enabled(struct trbe_cpudata *cpudata, u64 trblimitr)
 	 */
 	trblimitr |= TRBLIMITR_EL1_E;
 	write_sysreg_s(trblimitr, SYS_TRBLIMITR_EL1);
+	kvm_enable_trbe();
 
 	/* Synchronize the TRBE enable event */
 	isb();
@@ -239,6 +241,7 @@ static inline void set_trbe_disabled(struct trbe_cpudata *cpudata)
 	 */
 	trblimitr &= ~TRBLIMITR_EL1_E;
 	write_sysreg_s(trblimitr, SYS_TRBLIMITR_EL1);
+	kvm_disable_trbe();
 
 	if (trbe_needs_drain_after_disable(cpudata))
 		trbe_drain_buffer();
-- 
2.34.1