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authorOliver Upton <oliver.upton@linux.dev>2025-03-05 12:26:33 -0800
committerOliver Upton <oliver.upton@linux.dev>2025-03-11 12:54:29 -0700
commita38b67d1518331a4147c52c4fa563846ea0969f9 (patch)
tree61e203bb4f9c30b457b7a55faf289de4bb4aeefe
parent6f34024d185e2fa6636c660431c4595a6529328d (diff)
KVM: arm64: Drop kvm_arm_pmu_available static key
With the PMUv3 cpucap, kvm_arm_pmu_available is no longer used in the hot path of guest entry/exit. On top of that, guest support for PMUv3 may not correlate with host support for the feature, e.g. on IMPDEF hardware. Throw out the static key and just inspect the list of PMUs to determine if PMUv3 is supported for KVM guests. Tested-by: Janne Grunau <j@jannau.net> Reviewed-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20250305202641.428114-7-oliver.upton@linux.dev Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
-rw-r--r--arch/arm64/kernel/image-vars.h5
-rw-r--r--arch/arm64/kvm/arm.c4
-rw-r--r--arch/arm64/kvm/pmu-emul.c11
-rw-r--r--include/kvm/arm_pmu.h10
4 files changed, 10 insertions, 20 deletions
diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index ef3a69cc398e..e705c64138ce 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -112,11 +112,6 @@ KVM_NVHE_ALIAS(broken_cntvoff_key);
KVM_NVHE_ALIAS(__start___kvm_ex_table);
KVM_NVHE_ALIAS(__stop___kvm_ex_table);
-/* PMU available static key */
-#ifdef CONFIG_HW_PERF_EVENTS
-KVM_NVHE_ALIAS(kvm_arm_pmu_available);
-#endif
-
/* Position-independent library routines */
KVM_NVHE_ALIAS_HYP(clear_page, __pi_clear_page);
KVM_NVHE_ALIAS_HYP(copy_page, __pi_copy_page);
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index b8e55a441282..dc27d4eb503a 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -366,7 +366,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
r = get_num_wrps();
break;
case KVM_CAP_ARM_PMU_V3:
- r = kvm_arm_support_pmu_v3();
+ r = kvm_supports_guest_pmuv3();
break;
case KVM_CAP_ARM_INJECT_SERROR_ESR:
r = cpus_have_final_cap(ARM64_HAS_RAS_EXTN);
@@ -1388,7 +1388,7 @@ static unsigned long system_supported_vcpu_features(void)
if (!cpus_have_final_cap(ARM64_HAS_32BIT_EL1))
clear_bit(KVM_ARM_VCPU_EL1_32BIT, &features);
- if (!kvm_arm_support_pmu_v3())
+ if (!kvm_supports_guest_pmuv3())
clear_bit(KVM_ARM_VCPU_PMU_V3, &features);
if (!system_supports_sve())
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 62349b670cf9..120f48136a0f 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -17,8 +17,6 @@
#define PERF_ATTR_CFG1_COUNTER_64BIT BIT(0)
-DEFINE_STATIC_KEY_FALSE(kvm_arm_pmu_available);
-
static LIST_HEAD(arm_pmus);
static DEFINE_MUTEX(arm_pmus_lock);
@@ -26,6 +24,12 @@ 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]);
@@ -795,9 +799,6 @@ void kvm_host_pmu_init(struct arm_pmu *pmu)
entry->arm_pmu = pmu;
list_add_tail(&entry->entry, &arm_pmus);
- if (list_is_singular(&arm_pmus))
- static_branch_enable(&kvm_arm_pmu_available);
-
out_unlock:
mutex_unlock(&arm_pmus_lock);
}
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 3a8edd78240f..58fc7f932b3f 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -37,13 +37,7 @@ struct arm_pmu_entry {
struct arm_pmu *arm_pmu;
};
-DECLARE_STATIC_KEY_FALSE(kvm_arm_pmu_available);
-
-static __always_inline bool kvm_arm_support_pmu_v3(void)
-{
- return static_branch_likely(&kvm_arm_pmu_available);
-}
-
+bool kvm_supports_guest_pmuv3(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);
@@ -102,7 +96,7 @@ void kvm_pmu_nested_transition(struct kvm_vcpu *vcpu);
struct kvm_pmu {
};
-static inline bool kvm_arm_support_pmu_v3(void)
+static inline bool kvm_supports_guest_pmuv3(void)
{
return false;
}