On 28/7/2022 7:34 am, Sean Christopherson wrote:
Refresh the PMU if userspace modifies MSR_IA32_PERF_CAPABILITIES. KVM
consumes the vCPU's PERF_CAPABILITIES when enumerating PEBS support, but
relies on CPUID updates to refresh the PMU. I.e. KVM will do the wrong
thing if userspace stuffs PERF_CAPABILITIES _after_ setting guest CPUID.
Unwise userspace should reap its consequences if it does not break KVM or host.
When a guest feature can be defined/controlled by multiple KVM APIs entries,
(such as SET_CPUID2, msr_feature, KVM_CAP, module_para), should KVM
define the priority of these APIs (e.g. whether they can override each other) ?
Removing this ambiguity ensures consistency in the architecture and behavior of
all KVM features.
Any further performance optimizations can be based on these finalized values as
you do.
Opportunistically fix a curly-brace indentation.
Fixes: c59a1f106f5c ("KVM: x86/pmu: Add IA32_PEBS_ENABLE MSR emulation for extended PEBS")
Cc: Like Xu <like.xu.linux@xxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5366f884e9a7..362c538285db 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3543,9 +3543,9 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 1;
vcpu->arch.perf_capabilities = data;
-
+ kvm_pmu_refresh(vcpu);
I had proposed this diff but was met with silence.
return 0;
- }
+ }
case MSR_EFER:
return set_efer(vcpu, msr_info);
case MSR_K7_HWCR:
