Commit 145dfad9 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: VMX: Advertise PMU LBRs if and only if perf supports LBRs 



Advertise LBR support to userspace via MSR_IA32_PERF_CAPABILITIES if and
only if perf fully supports LBRs.  Perf may disable LBRs (by zeroing the
number of LBRs) even on platforms the allegedly support LBRs, e.g. if
probing any LBR MSRs during setup fails.

Fixes: be635e34 ("KVM: vmx/pmu: Expose LBR_FMT in the MSR_IA32_PERF_CAPABILITIES")
Reported-by: default avatarLike Xu <like.xu.linux@gmail.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20221006000314.73240-3-seanjc@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 73536338

arch/x86/kvm/vmx/capabilities.h

+3 −1
Original line number Diff line number Diff line
@@ -400,6 +400,7 @@ static inline bool vmx_pebs_supported(void) 
static inline u64 vmx_get_perf_capabilities(void)

{

	u64 perf_cap = PMU_CAP_FW_WRITES;

	struct x86_pmu_lbr lbr;

	u64 host_perf_cap = 0;



	if (!enable_pmu)
@@ -408,6 +409,7 @@ static inline u64 vmx_get_perf_capabilities(void) 
	if (boot_cpu_has(X86_FEATURE_PDCM))

		rdmsrl(MSR_IA32_PERF_CAPABILITIES, host_perf_cap);



	if (x86_perf_get_lbr(&lbr) >= 0 && lbr.nr)

		perf_cap |= host_perf_cap & PMU_CAP_LBR_FMT;



	if (vmx_pebs_supported()) {