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    SubjectRe: [PATCH v2 09/15] KVM: x86: Refine the matching and clearing logic for supported_xss
    On Thu, Nov 24, 2022, Yang Weijiang wrote:
    > 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: Paolo Bonzini <pbonzini@redhat.com>
    > Signed-off-by: Yang Weijiang <weijiang.yang@intel.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 9bd52ad3bbf4..2ab4c33b5008 100644
    > --- a/arch/x86/kvm/vmx/vmx.c
    > +++ b/arch/x86/kvm/vmx/vmx.c
    > @@ -7738,9 +7738,10 @@ static __init void vmx_set_cpu_caps(void)
    > kvm_cpu_cap_set(X86_FEATURE_UMIP);
    >
    > /* CPUID 0xD.1 */
    > - kvm_caps.supported_xss = 0;

    This needs to stay until VMX actually supports something.

    > - if (!cpu_has_vmx_xsaves())
    > + if (!cpu_has_vmx_xsaves()) {
    > kvm_cpu_cap_clear(X86_FEATURE_XSAVES);
    > + kvm_caps.supported_xss = 0;

    This is already handled in common KVM.

    > + }
    >
    > /* 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 74c858eaa1ea..889be0c9176d 100644
    > --- a/arch/x86/kvm/x86.c
    > +++ b/arch/x86/kvm/x86.c
    > @@ -217,6 +217,8 @@ 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);
    >
    > @@ -11999,8 +12001,10 @@ 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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