[PATCH 04/15] KVM: x86/pmu: Add PMC bitmap accessor helpers

[Zide Chen]

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

pmu->all_valid_pmc_mask already holds a bitmap indicating both fixed
and general-purpose counters, and loops over valid counters can be
done via pmu->all_valid_pmc_mask 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@xxxxxxxxxxxxxxx>
Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
Signed-off-by: Zide Chen <zide.chen@xxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |  5 ++-
 arch/x86/kvm/pmu.h              | 55 +++++++++++++++++++++++++++++----
 2 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 395b6f20e9ac..f648dc168685 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -643,7 +643,10 @@ struct kvm_pmu {
 		DECLARE_BITMAP(reprogram_pmi, X86_PMC_IDX_MAX);
 		atomic64_t __reprogram_pmi;
 	};
-	DECLARE_BITMAP(all_valid_pmc_mask, X86_PMC_IDX_MAX);
+	union {
+		DECLARE_BITMAP(all_valid_pmc_mask, X86_PMC_IDX_MAX);
+		u64 all_valid_pmc_mask64;
+	};
 	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.h b/arch/x86/kvm/pmu.h
index cdbefda844b9..95dc95a9ae37 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -88,6 +88,32 @@ 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->all_valid_pmc_mask64 &
+	       GENMASK_ULL(KVM_MAX_NR_GP_COUNTERS - 1, 0);
+}
+
+static inline unsigned long kvm_fixed_pmc_mask(struct kvm_pmu *pmu)
+{
+	return (pmu->all_valid_pmc_mask64 >> KVM_FIXED_PMC_BASE_IDX) &
+		GENMASK_ULL(KVM_MAX_NR_FIXED_COUNTERS - 1, 0);
+}
+
+static inline bool kvm_gp_pmc_supported(struct kvm_pmu *pmu, unsigned int idx)
+{
+	unsigned long bitmap = kvm_gp_pmc_mask(pmu);
+
+	return idx < KVM_MAX_NR_GP_COUNTERS && test_bit(idx, &bitmap);
+}
+
+static inline bool kvm_fixed_pmc_supported(struct kvm_pmu *pmu, unsigned int idx)
+{
+	unsigned long bitmap = kvm_fixed_pmc_mask(pmu);
+
+	return idx < KVM_MAX_NR_FIXED_COUNTERS && test_bit(idx, &bitmap);
+}
+
 /*
  * 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 +130,11 @@ 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_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_fixed_pmc_supported(pmu, idx))
 		return &pmu->fixed_counters[idx];
 
 	return NULL;
@@ -120,6 +146,17 @@ static inline struct kvm_pmc *kvm_pmc_idx_to_pmc(struct kvm_pmu *pmu, int idx)
 			continue;				\
 		else						\
 
+/*
+ * @mask must be an lvalue of type unsigned long because for_each_set_bit()
+ * takes its address.
+ *
+ * @type is token-pasted into KVM_MAX_NR_##type##_COUNTERS to match one of the
+ * counter defines, e.g. GP, FIXED, AMD_GP, INTEL_GP, or INTEL_FIXED. This
+ * reflects what KVM supports, not the underlying host's PMU capabilities.
+ */
+#define kvm_for_each_set_pmc_idx(i, mask, type)		\
+	for_each_set_bit((i), &(mask), KVM_MAX_NR_##type##_COUNTERS)
+
 static inline u64 pmc_bitmask(struct kvm_pmc *pmc)
 {
 	struct kvm_pmu *pmu = pmc_to_pmu(pmc);
@@ -168,9 +205,12 @@ 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_gp_pmc_supported(pmu, index))
+			return NULL;
 
 		return &pmu->gp_counters[index];
 	}
@@ -183,9 +223,12 @@ 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_fixed_pmc_supported(pmu, index))
+			return NULL;
 
 		return &pmu->fixed_counters[index];
 	}
-- 
2.54.0