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| author | Sean Christopherson <seanjc@google.com> | 2022-10-06 02:03:07 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-11-09 18:31:11 +0100 |
| commit | 0b9ca98b722969660ad98b39f766a561ccb39f5f (patch) | |
| tree | 8124d277785370e6c261066f94dfb63633abebd7 /arch/x86/kvm/vmx/capabilities.h | |
| parent | Merge tag 'kvm-s390-master-6.1-1' of https://git.kernel.org/pub/scm/linux/ker... (diff) | |
| download | linux-0b9ca98b722969660ad98b39f766a561ccb39f5f.tar.xz linux-0b9ca98b722969660ad98b39f766a561ccb39f5f.zip | |
perf/x86/core: Zero @lbr instead of returning -1 in x86_perf_get_lbr() stub
Drop the return value from x86_perf_get_lbr() and have the stub zero out
the @lbr structure instead of returning -1 to indicate "no LBR support".
KVM doesn't actually check the return value, and instead subtly relies on
zeroing the number of LBRs in intel_pmu_init().
Formalize "nr=0 means unsupported" so that KVM doesn't need to add a
pointless check on the return value to fix KVM's benign bug.
Note, the stub is necessary even though KVM x86 selects PERF_EVENTS and
the caller exists only when CONFIG_KVM_INTEL=y. Despite the name,
KVM_INTEL doesn't strictly require CPU_SUP_INTEL, it can be built with
any of INTEL || CENTAUR || ZHAOXIN CPUs.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20221006000314.73240-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/vmx/capabilities.h')
| -rw-r--r-- | arch/x86/kvm/vmx/capabilities.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h index 07254314f3dd..479124e49bbd 100644 --- a/arch/x86/kvm/vmx/capabilities.h +++ b/arch/x86/kvm/vmx/capabilities.h @@ -407,7 +407,8 @@ 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) + x86_perf_get_lbr(&lbr); + if (lbr.nr) perf_cap |= host_perf_cap & PMU_CAP_LBR_FMT; if (vmx_pebs_supported()) { |