Re: [PATCH v2 09/15] KVM: x86: Refine the matching and clearing logic for supported_xss

[Yang, Weijiang]

On 1/28/2023 5:46 AM, Sean Christopherson wrote:
> On Thu, Nov 24, 2022, Yang Weijiang wrote:
> > From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
> > Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
> > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
> > ---
> >   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.

Will modify this patch.


> > -	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