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    Subject[PATCH 09/15] KVM: x86: Refine the matching and clearing logic for supported_xss
    Date
    From: Paolo Bonzini <pbonzini@redhat.com>

    Refine the code path of the existing clearing of supported_xss in this way:
    initialize the supported_xss with the filter of KVM_SUPPORTED_XSS mask and
    update its value in a bit clear manner (rather than bit setting).

    Suggested-by: Sean Christopherson <seanjc@google.com>
    Signed-off-by: Like Xu <like.xu@linux.intel.com>
    Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
    Message-Id: <20220517154100.29983-10-weijiang.yang@intel.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    ---
    arch/x86/kvm/vmx/vmx.c | 5 +++--
    arch/x86/kvm/x86.c | 6 +++++-
    2 files changed, 8 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
    index 77bad663d804..32e41bd217e3 100644
    --- a/arch/x86/kvm/vmx/vmx.c
    +++ b/arch/x86/kvm/vmx/vmx.c
    @@ -7717,9 +7717,10 @@ static __init void vmx_set_cpu_caps(void)
    kvm_cpu_cap_set(X86_FEATURE_UMIP);

    /* CPUID 0xD.1 */
    - kvm_caps.supported_xss = 0;
    - if (!cpu_has_vmx_xsaves())
    + if (!cpu_has_vmx_xsaves()) {
    kvm_cpu_cap_clear(X86_FEATURE_XSAVES);
    + kvm_caps.supported_xss = 0;
    + }

    /* CPUID 0x80000001 and 0x7 (RDPID) */
    if (!cpu_has_vmx_rdtscp()) {
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index b3d2a7ad1d18..19cb5840300b 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -213,6 +213,8 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs;
    | XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
    | XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE)

    +#define KVM_SUPPORTED_XSS 0
    +
    u64 __read_mostly host_efer;
    EXPORT_SYMBOL_GPL(host_efer);

    @@ -11965,8 +11967,10 @@ int kvm_arch_hardware_setup(void *opaque)

    rdmsrl_safe(MSR_EFER, &host_efer);

    - if (boot_cpu_has(X86_FEATURE_XSAVES))
    + if (boot_cpu_has(X86_FEATURE_XSAVES)) {
    rdmsrl(MSR_IA32_XSS, host_xss);
    + kvm_caps.supported_xss = host_xss & KVM_SUPPORTED_XSS;
    + }

    kvm_init_pmu_capability();

    --
    2.27.0
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