Messages in this thread | | | Subject | Re: [PATCH] KVM: x86: add hint to skip hidden rdpkru under kvm_load_host_xsave_state | From | Paolo Bonzini <> | Date | Fri, 7 May 2021 18:52:11 +0200 |
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Nice one. The patch can be made simpler though (I think).
On 07/05/21 18:44, Jon Kohler wrote: @@ -122,7 +124,7 @@ static inline u32 rdpkru(void) > return 0; > } > > -static inline void __write_pkru(u32 pkru) > +static inline void __write_pkru(u32 pkru, bool skip_comparison) > { > } > #endif > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index cebdaa1e3cf5..cd95adbd140c 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -912,10 +912,10 @@ void kvm_load_guest_xsave_state(struct kvm_vcpu *vcpu) > } > > if (static_cpu_has(X86_FEATURE_PKU) && > - (kvm_read_cr4_bits(vcpu, X86_CR4_PKE) || > - (vcpu->arch.xcr0 & XFEATURE_MASK_PKRU)) && > - vcpu->arch.pkru != vcpu->arch.host_pkru) > - __write_pkru(vcpu->arch.pkru); > + vcpu->arch.pkru != vcpu->arch.host_pkru && > + ((vcpu->arch.xcr0 & XFEATURE_MASK_PKRU) || > + kvm_read_cr4_bits(vcpu, X86_CR4_PKE))) > + __write_pkru(vcpu->arch.pkru, false);
This can be optimized as well, can't it? This means that the only case that needs the rdpkru is in switch_fpu_finish, and __write_pkru can be removed completely:
- do the rdpkru+wrpkru in switch_fpu_finish
- just use wrpkru in KVM
Paolo
> } > EXPORT_SYMBOL_GPL(kvm_load_guest_xsave_state); > > @@ -925,11 +925,11 @@ void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu) > return; > > if (static_cpu_has(X86_FEATURE_PKU) && > - (kvm_read_cr4_bits(vcpu, X86_CR4_PKE) || > - (vcpu->arch.xcr0 & XFEATURE_MASK_PKRU))) { > + ((vcpu->arch.xcr0 & XFEATURE_MASK_PKRU) || > + kvm_read_cr4_bits(vcpu, X86_CR4_PKE))) { > vcpu->arch.pkru = rdpkru(); > if (vcpu->arch.pkru != vcpu->arch.host_pkru) > - __write_pkru(vcpu->arch.host_pkru); > + __write_pkru(vcpu->arch.host_pkru, true); > } > > if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE)) { > -- > 2.30.1 (Apple Git-130) >
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