KVM: x86/pmu: Zero out PMU metadata on AMD if PMU is disabled

Move the purging of common PMU metadata from intel_pmu_refresh() to
kvm_pmu_refresh(), and invoke the vendor refresh() hook if and only if
the VM is supposed to have a vPMU.

KVM already denies access to the PMU based on kvm->arch.enable_pmu, as
get_gp_pmc_amd() returns NULL for all PMCs in that case, i.e. KVM already
violates AMD's architecture by not virtualizing a PMU (kernels have long
since learned to not panic when the PMU is unavailable).  But configuring
the PMU as if it were enabled causes unwanted side effects, e.g. calls to
kvm_pmu_trigger_event() waste an absurd number of cycles due to the
all_valid_pmc_idx bitmap being non-zero.

Fixes: b1d66dad65dc ("KVM: x86/svm: Add module param to control PMU virtualization")
Reported-by: Konstantin Khorenko <khorenko@virtuozzo.com>
Closes: https://lore.kernel.org/all/20231109180646.2963718-2-khorenko@virtuozzo.com
Link: https://lore.kernel.org/r/20231110022857.1273836-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 09b0feb975c3b7dd639b8e326caf461d28562567..4d4366c6f7cd4d59d90730008707936a79c45e49 100644 (file)
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -749,6 +749,8 @@ static void kvm_pmu_reset(struct kvm_vcpu *vcpu)
  */
 void kvm_pmu_refresh(struct kvm_vcpu *vcpu)
 {
+       struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
+
        if (KVM_BUG_ON(kvm_vcpu_has_run(vcpu), vcpu->kvm))
                return;
 
@@ -758,8 +760,22 @@ void kvm_pmu_refresh(struct kvm_vcpu *vcpu)
         */
        kvm_pmu_reset(vcpu);
 
-       bitmap_zero(vcpu_to_pmu(vcpu)->all_valid_pmc_idx, X86_PMC_IDX_MAX);
-       static_call(kvm_x86_pmu_refresh)(vcpu);
+       pmu->version = 0;
+       pmu->nr_arch_gp_counters = 0;
+       pmu->nr_arch_fixed_counters = 0;
+       pmu->counter_bitmask[KVM_PMC_GP] = 0;
+       pmu->counter_bitmask[KVM_PMC_FIXED] = 0;
+       pmu->reserved_bits = 0xffffffff00200000ull;
+       pmu->raw_event_mask = X86_RAW_EVENT_MASK;
+       pmu->global_ctrl_mask = ~0ull;
+       pmu->global_status_mask = ~0ull;
+       pmu->fixed_ctr_ctrl_mask = ~0ull;
+       pmu->pebs_enable_mask = ~0ull;
+       pmu->pebs_data_cfg_mask = ~0ull;
+       bitmap_zero(pmu->all_valid_pmc_idx, X86_PMC_IDX_MAX);
+
+       if (vcpu->kvm->arch.enable_pmu)
+               static_call(kvm_x86_pmu_refresh)(vcpu);
 }
 
 void kvm_pmu_init(struct kvm_vcpu *vcpu)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index b41bdb0a099507b09d6e45734c3eac3096a481d0..a87f4725a9bedc069192a71fcce65d7194b2fa7c 100644 (file)
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -471,19 +471,6 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
        u64 counter_mask;
        int i;
 
-       pmu->nr_arch_gp_counters = 0;
-       pmu->nr_arch_fixed_counters = 0;
-       pmu->counter_bitmask[KVM_PMC_GP] = 0;
-       pmu->counter_bitmask[KVM_PMC_FIXED] = 0;
-       pmu->version = 0;
-       pmu->reserved_bits = 0xffffffff00200000ull;
-       pmu->raw_event_mask = X86_RAW_EVENT_MASK;
-       pmu->global_ctrl_mask = ~0ull;
-       pmu->global_status_mask = ~0ull;
-       pmu->fixed_ctr_ctrl_mask = ~0ull;
-       pmu->pebs_enable_mask = ~0ull;
-       pmu->pebs_data_cfg_mask = ~0ull;
-
        memset(&lbr_desc->records, 0, sizeof(lbr_desc->records));
 
        /*
@@ -495,8 +482,9 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
                return;
 
        entry = kvm_find_cpuid_entry(vcpu, 0xa);
-       if (!entry || !vcpu->kvm->arch.enable_pmu)
+       if (!entry)
                return;
+
        eax.full = entry->eax;
        edx.full = entry->edx;