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

commit 098f4c061ea10b777033b71c10bd9fd706820ee9 upstream.

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index cb547a083381273ecf96e0d2917768033d18287e..663e8a6f03b3bc38ec56aa7b46520f6088dd1c6e 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7749,9 +7749,11 @@ 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;