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

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>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d7bf14abdba1df6e91df8e96e23b935fe788b896..c18f74899f011d5a75b3f7cecf6d69e6388154f6 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7793,9 +7793,11 @@ 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;