KVM: x86/pmu: Disallow legacy LBRs if architectural LBRs are available

[ Upstream commit 098f4c061ea10b777033b71c10bd9fd706820ee9 ]

Disallow enabling LBR support if the CPU supports architectural LBRs.
Traditional LBR support is absent on CPU models that have architectural
LBRs, and KVM doesn't yet support arch LBRs, i.e. KVM will pass through
non-existent MSRs if userspace enables LBRs for the guest.

Cc: stable@vger.kernel.org
Cc: Yang Weijiang <weijiang.yang@intel.com>
Cc: Like Xu <like.xu.linux@gmail.com>
Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Fixes: be635e34c284 ("KVM: vmx/pmu: Expose LBR_FMT in the MSR_IA32_PERF_CAPABILITIES")
Tested-by: Like Xu <likexu@tencent.com>
Link: https://lore.kernel.org/r/20230128001427.2548858-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 8ad5992f61340e144f7116b341884f578023f246..5db21d9ef671044e7d2700751f974493f2e89c40 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7714,9 +7714,11 @@ static u64 vmx_get_perf_capabilities(void)
        if (boot_cpu_has(X86_FEATURE_PDCM))
                rdmsrl(MSR_IA32_PERF_CAPABILITIES, host_perf_cap);
 
-       x86_perf_get_lbr(&lbr);
-       if (lbr.nr)
-               perf_cap |= host_perf_cap & PMU_CAP_LBR_FMT;
+       if (!cpu_feature_enabled(X86_FEATURE_ARCH_LBR)) {
+               x86_perf_get_lbr(&lbr);
+               if (lbr.nr)
+                       perf_cap |= host_perf_cap & PMU_CAP_LBR_FMT;
+       }
 
        if (vmx_pebs_supported()) {
                perf_cap |= host_perf_cap & PERF_CAP_PEBS_MASK;