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    Subject[PATCH 03/26] KVM: x86: Snapshot MSR index in a local variable when processing lists
    Date
    Snapshot the MSR index when processing the virtualized and emulated MSR
    lists in kvm_init_msr_list() to improve code readability, particularly
    in the RTIT and PerfMon MSR checks.

    No functional change intended.

    Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
    ---
    arch/x86/kvm/x86.c | 22 +++++++++++++---------
    1 file changed, 13 insertions(+), 9 deletions(-)

    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index 24597526b5de..3d4a5326d84e 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -5214,7 +5214,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
    static void kvm_init_msr_list(void)
    {
    struct x86_pmu_capability x86_pmu;
    - u32 dummy[2];
    + u32 dummy[2], msr_index;
    unsigned i;

    BUILD_BUG_ON_MSG(INTEL_PMC_MAX_FIXED != 4,
    @@ -5227,14 +5227,16 @@ static void kvm_init_msr_list(void)
    num_msr_based_features = 0;

    for (i = 0; i < ARRAY_SIZE(msrs_to_save_all); i++) {
    - if (rdmsr_safe(msrs_to_save_all[i], &dummy[0], &dummy[1]) < 0)
    + msr_index = msrs_to_save_all[i];
    +
    + if (rdmsr_safe(msr_index, &dummy[0], &dummy[1]) < 0)
    continue;

    /*
    * Even MSRs that are valid in the host may not be exposed
    * to the guests in some cases.
    */
    - switch (msrs_to_save_all[i]) {
    + switch (msr_index) {
    case MSR_IA32_BNDCFGS:
    if (!kvm_mpx_supported())
    continue;
    @@ -5262,17 +5264,17 @@ static void kvm_init_msr_list(void)
    break;
    case MSR_IA32_RTIT_ADDR0_A ... MSR_IA32_RTIT_ADDR3_B:
    if (!kvm_x86_ops->pt_supported() ||
    - msrs_to_save_all[i] - MSR_IA32_RTIT_ADDR0_A >=
    + msr_index - MSR_IA32_RTIT_ADDR0_A >=
    intel_pt_validate_hw_cap(PT_CAP_num_address_ranges) * 2)
    continue;
    break;
    case MSR_ARCH_PERFMON_PERFCTR0 ... MSR_ARCH_PERFMON_PERFCTR0 + 17:
    - if (msrs_to_save_all[i] - MSR_ARCH_PERFMON_PERFCTR0 >=
    + if (msr_index - MSR_ARCH_PERFMON_PERFCTR0 >=
    min(INTEL_PMC_MAX_GENERIC, x86_pmu.num_counters_gp))
    continue;
    break;
    case MSR_ARCH_PERFMON_EVENTSEL0 ... MSR_ARCH_PERFMON_EVENTSEL0 + 17:
    - if (msrs_to_save_all[i] - MSR_ARCH_PERFMON_EVENTSEL0 >=
    + if (msr_index - MSR_ARCH_PERFMON_EVENTSEL0 >=
    min(INTEL_PMC_MAX_GENERIC, x86_pmu.num_counters_gp))
    continue;
    break;
    @@ -5280,14 +5282,16 @@ static void kvm_init_msr_list(void)
    break;
    }

    - msrs_to_save[num_msrs_to_save++] = msrs_to_save_all[i];
    + msrs_to_save[num_msrs_to_save++] = msr_index;
    }

    for (i = 0; i < ARRAY_SIZE(emulated_msrs_all); i++) {
    - if (!kvm_x86_ops->has_emulated_msr(emulated_msrs_all[i]))
    + msr_index = emulated_msrs_all[i];
    +
    + if (!kvm_x86_ops->has_emulated_msr(msr_index))
    continue;

    - emulated_msrs[num_emulated_msrs++] = emulated_msrs_all[i];
    + emulated_msrs[num_emulated_msrs++] = msr_index;
    }

    for (i = 0; i < ARRAY_SIZE(msr_based_features_all); i++) {
    --
    2.24.1
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