This is a note to let you know that I've just added the patch titled
KVM: x86/pmu: Disallow legacy LBRs if architectural LBRs are available
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-pmu-disallow-legacy-lbrs-if-architectural-lbrs-are-available.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 098f4c061ea10b777033b71c10bd9fd706820ee9 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@xxxxxxxxxx>
Date: Sat, 28 Jan 2023 00:14:27 +0000
Subject: KVM: x86/pmu: Disallow legacy LBRs if architectural LBRs are available
From: Sean Christopherson <seanjc@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Cc: Yang Weijiang <weijiang.yang@xxxxxxxxx>
Cc: Like Xu <like.xu.linux@xxxxxxxxx>
Reported-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Fixes: be635e34c284 ("KVM: vmx/pmu: Expose LBR_FMT in the MSR_IA32_PERF_CAPABILITIES")
Tested-by: Like Xu <likexu@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230128001427.2548858-1-seanjc@xxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d7bf14abdba1..c18f74899f01 100644
--- 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;
--
2.40.1
Patches currently in stable-queue which might be from seanjc@xxxxxxxxxx are
queue-6.1/kvm-x86-pmu-disallow-legacy-lbrs-if-architectural-lbrs-are-available.patch
queue-6.1/kvm-nvmx-emulate-nops-in-l2-and-pause-if-it-s-not-intercepted.patch
