lkml.org 
[lkml]   [2022]   [Jun]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    Subject[PATCH v5 07/15] KVM: VMX: Add helper to check if the guest PMU has PERF_GLOBAL_CTRL
    From
    Add a helper to check of the guest PMU has PERF_GLOBAL_CTRL, which is
    unintuitive _and_ diverges from Intel's architecturally defined behavior.
    Even worse, KVM currently implements the check using two different, but
    equivalent checksand , _and_ there has been at least one attempt to add a
    _third_ flavor.

    Link: https://lore.kernel.org/all/Yk4ugOETeo%2FqDRbW@google.com
    Signed-off-by: Sean Christopherson <seanjc@google.com>
    ---
    arch/x86/kvm/vmx/pmu_intel.c | 4 ++--
    arch/x86/kvm/vmx/vmx.h | 12 ++++++++++++
    2 files changed, 14 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
    index 5b85320fc9f1..6ce3b066f7d9 100644
    --- a/arch/x86/kvm/vmx/pmu_intel.c
    +++ b/arch/x86/kvm/vmx/pmu_intel.c
    @@ -111,7 +111,7 @@ static bool intel_pmc_is_enabled(struct kvm_pmc *pmc)
    {
    struct kvm_pmu *pmu = pmc_to_pmu(pmc);

    - if (pmu->version < 2)
    + if (!intel_pmu_has_perf_global_ctrl(pmu))
    return true;

    return test_bit(pmc->idx, (unsigned long *)&pmu->global_ctrl);
    @@ -208,7 +208,7 @@ static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr, bool host_initiat
    case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
    if (host_initiated)
    return true;
    - return pmu->version > 1;
    + return intel_pmu_has_perf_global_ctrl(pmu);
    break;
    case MSR_IA32_PEBS_ENABLE:
    if (host_initiated)
    diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
    index 576fed7e33de..215f17eb6732 100644
    --- a/arch/x86/kvm/vmx/vmx.h
    +++ b/arch/x86/kvm/vmx/vmx.h
    @@ -91,6 +91,18 @@ union vmx_exit_reason {
    u32 full;
    };

    +static inline bool intel_pmu_has_perf_global_ctrl(struct kvm_pmu *pmu)
    +{
    + /*
    + * Architecturally, Intel's SDM states that IA32_PERF_GLOBAL_CTRL is
    + * supported if "CPUID.0AH: EAX[7:0] > 0", i.e. if the PMU version is
    + * greater than zero. However, KVM only exposes and emulates the MSR
    + * to/for the guest if the guest PMU supports at least "Architectural
    + * Performance Monitoring Version 2".
    + */
    + return pmu->version > 1;
    +}
    +
    #define vcpu_to_lbr_desc(vcpu) (&to_vmx(vcpu)->lbr_desc)
    #define vcpu_to_lbr_records(vcpu) (&to_vmx(vcpu)->lbr_desc.records)

    --
    2.36.1.255.ge46751e96f-goog
    \
     
     \ /
      Last update: 2022-06-08 03:35    [W:4.130 / U:0.040 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site