KVM: VMX: Adjust number of LBR records for PERF_CAPABILITIES at refresh

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Now that the PMU is refreshed when MSR_IA32_PERF_CAPABILITIES is written
by host userspace, zero out the number of LBR records for a vCPU during
PMU refresh if PMU_CAP_LBR_FMT is not set in PERF_CAPABILITIES instead of
handling the check at run-time.

guest_cpuid_has() is expensive due to the linear search of guest CPUID
entries, intel_pmu_lbr_is_enabled() is checked on every VM-Enter, _and_
simply enumerating the same "Model" as the host causes KVM to set the
number of LBR records to a non-zero value.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220727233424.2968356-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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Sean Christopherson 2022-07-27 23:34:24 +00:00 • committed by Paolo Bonzini

parent 7de8e5b6b1

commit 6348aafa8d

2 changed files with 8 additions and 11 deletions

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12

arch/x86/kvm/vmx/pmu_intel.c

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7

arch/x86/kvm/vmx/vmx.h

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