Reset vcpu->arch.perf_capabilities to 0 if PDCM is disabled in guest cpuid. Without this, there is an issue in live migration. In particular, to migrate a VM with no PDCM enabled, VMM on the source is able to retrieve a non-zero value by reading the MSR_IA32_PERF_CAPABILITIES. However, VMM on the target is unable to set the value. This creates confusions on the user side. Fundamentally, it is because vcpu->arch.perf_capabilities as the cached value of MSR_IA32_PERF_CAPABILITIES is incorrect, and there is nothing wrong on the kvm_get_msr_common() which just reads vcpu->arch.perf_capabilities. Fix the issue by adding the reset code in kvm_vcpu_after_set_cpuid(), i.e. early in VM setup time. Cc: Aaron Lewis <aaronlewis@xxxxxxxxxx> Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx> --- arch/x86/kvm/cpuid.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index adba49afb5fe..416bee03c42a 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -369,6 +369,9 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu); vcpu->arch.reserved_gpa_bits = kvm_vcpu_reserved_gpa_bits_raw(vcpu); + /* Reset MSR_IA32_PERF_CAPABILITIES guest value to 0 if PDCM is off. */ + if (!guest_cpuid_has(vcpu, X86_FEATURE_PDCM)) + vcpu->arch.perf_capabilities = 0; kvm_pmu_refresh(vcpu); vcpu->arch.cr4_guest_rsvd_bits = __cr4_reserved_bits(guest_cpuid_has, vcpu); -- 2.43.0.429.g432eaa2c6b-goog
