[PATCH v3 04/18] KVM: x86/pmu: Add PMC bitmap accessor helpers

[Zide Chen <zide.chen@intel.com>]

pmu->nr_arch_{gp,fixed}_counters is not able to represent that a PMU
may include non-contiguous GP or fixed counters.

pmu->pmc_exists already holds a bitmap indicating both fixed and
general-purpose counters, and loops over valid counters can be done via
pmu->pmc_exists alone. Extend it to a union so that the u64 alias is
available for convenient mask arithmetic operations.

Add the necessary helpers to prepare for bitmap-based PMC counter
implementation.

No functional change intended.

Co-developed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Zide Chen <zide.chen@intel.com>
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
---
v3:
- Add BUILD_BUG_ON(). (Jim)
v2:
- Rename kvm_{gp,fixed}_pmc_supported() to kvm_is_{gp,fixed}_pmc_supported()
  and simplify them by removing the temporary bitmap. (Sean)
- Split kvm_for_each_set_pmc_idx() to kvm_for_each_gp_counter()
  and kvm_for_each_fixed_counter(). (Sean)
---
 arch/x86/include/asm/kvm_host.h |  5 +++-
 arch/x86/kvm/pmu.c              |  2 ++
 arch/x86/kvm/pmu.h              | 53 +++++++++++++++++++++++++++++----
 3 files changed, 53 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b8875ed5502c..4f192429ed93 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -595,7 +595,10 @@ struct kvm_pmu {
 		DECLARE_BITMAP(reprogram_pmi, X86_PMC_IDX_MAX);
 		atomic64_t __reprogram_pmi;
 	};
-	DECLARE_BITMAP(pmc_exists, X86_PMC_IDX_MAX);
+	union {
+		DECLARE_BITMAP(pmc_exists, X86_PMC_IDX_MAX);
+		u64 pmc_exists64;
+	};
 	DECLARE_BITMAP(pmc_in_use, X86_PMC_IDX_MAX);
 
 	DECLARE_BITMAP(pmc_counting_instructions, X86_PMC_IDX_MAX);
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index cbd63329cf13..5e174d95f3b7 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -1024,6 +1024,8 @@ void kvm_pmu_init(struct kvm_vcpu *vcpu)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
 
+	BUILD_BUG_ON(sizeof(pmu->pmc_exists) != sizeof(pmu->pmc_exists64));
+
 	memset(pmu, 0, sizeof(*pmu));
 	kvm_pmu_call(init)(vcpu);
 }
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index 090c9bbb74f4..016935c3a8ec 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -88,6 +88,30 @@ static inline bool kvm_vcpu_has_mediated_pmu(struct kvm_vcpu *vcpu)
 	return enable_mediated_pmu && vcpu_to_pmu(vcpu)->version;
 }
 
+static inline unsigned long kvm_gp_pmc_mask(struct kvm_pmu *pmu)
+{
+	return pmu->pmc_exists64 &
+	       GENMASK_ULL(KVM_MAX_NR_GP_COUNTERS - 1, 0);
+}
+
+static inline unsigned long kvm_fixed_pmc_mask(struct kvm_pmu *pmu)
+{
+	return (pmu->pmc_exists64 >> KVM_FIXED_PMC_BASE_IDX) &
+	       GENMASK_ULL(KVM_MAX_NR_FIXED_COUNTERS - 1, 0);
+}
+
+static inline bool kvm_is_gp_pmc_supported(struct kvm_pmu *pmu, unsigned int idx)
+{
+	return idx < KVM_MAX_NR_GP_COUNTERS &&
+	       test_bit(idx, pmu->pmc_exists);
+}
+
+static inline bool kvm_is_fixed_pmc_supported(struct kvm_pmu *pmu, unsigned int idx)
+{
+	return idx < KVM_MAX_NR_FIXED_COUNTERS &&
+	       test_bit(KVM_FIXED_PMC_BASE_IDX + idx, pmu->pmc_exists);
+}
+
 /*
  * KVM tracks all counters in 64-bit bitmaps, with general purpose counters
  * mapped to bits 31:0 and fixed counters mapped to 63:32, e.g. fixed counter 0
@@ -104,11 +128,11 @@ static inline bool kvm_vcpu_has_mediated_pmu(struct kvm_vcpu *vcpu)
  */
 static inline struct kvm_pmc *kvm_pmc_idx_to_pmc(struct kvm_pmu *pmu, int idx)
 {
-	if (idx < pmu->nr_arch_gp_counters)
+	if (kvm_is_gp_pmc_supported(pmu, idx))
 		return &pmu->gp_counters[idx];
 
 	idx -= KVM_FIXED_PMC_BASE_IDX;
-	if (idx >= 0 && idx < pmu->nr_arch_fixed_counters)
+	if (kvm_is_fixed_pmc_supported(pmu, idx))
 		return &pmu->fixed_counters[idx];
 
 	return NULL;
@@ -120,6 +144,17 @@ static inline struct kvm_pmc *kvm_pmc_idx_to_pmc(struct kvm_pmu *pmu, int idx)
 			continue;				\
 		else						\
 
+/*
+ * @mask is expected to be a scalar unsigned long derived from pmu->pmc_exists,
+ * which is already constrained by KVM_MAX_NR_{AMD,INTEL}_{GP,FIXED}_COUNTERS,
+ * so iteration up to KVM's maximum counter count is safe.
+ */
+#define kvm_for_each_gp_counter(i, mask)	\
+	for_each_set_bit((i), &(mask), KVM_MAX_NR_GP_COUNTERS)
+
+#define kvm_for_each_fixed_counter(i, mask)	\
+	for_each_set_bit((i), &(mask), KVM_MAX_NR_FIXED_COUNTERS)
+
 static inline u64 pmc_bitmask(struct kvm_pmc *pmc)
 {
 	struct kvm_pmu *pmu = pmc_to_pmu(pmc);
@@ -168,9 +203,12 @@ static inline bool kvm_valid_perf_global_ctrl(struct kvm_pmu *pmu,
 static inline struct kvm_pmc *get_gp_pmc(struct kvm_pmu *pmu, u32 msr,
 					 u32 base)
 {
-	if (msr >= base && msr < base + pmu->nr_arch_gp_counters) {
+	if (msr >= base && msr < base + KVM_MAX_NR_GP_COUNTERS) {
 		u32 index = array_index_nospec(msr - base,
-					       pmu->nr_arch_gp_counters);
+					       KVM_MAX_NR_GP_COUNTERS);
+
+		if (!kvm_is_gp_pmc_supported(pmu, index))
+			return NULL;
 
 		return &pmu->gp_counters[index];
 	}
@@ -183,9 +221,12 @@ static inline struct kvm_pmc *get_fixed_pmc(struct kvm_pmu *pmu, u32 msr)
 {
 	int base = MSR_CORE_PERF_FIXED_CTR0;
 
-	if (msr >= base && msr < base + pmu->nr_arch_fixed_counters) {
+	if (msr >= base && msr < base + KVM_MAX_NR_FIXED_COUNTERS) {
 		u32 index = array_index_nospec(msr - base,
-					       pmu->nr_arch_fixed_counters);
+					       KVM_MAX_NR_FIXED_COUNTERS);
+
+		if (!kvm_is_fixed_pmc_supported(pmu, index))
+			return NULL;
 
 		return &pmu->fixed_counters[index];
 	}
-- 
2.56.0