Messages in this thread | | | Date | Wed, 19 Jan 2022 15:25:25 +0800 | Subject | Re: [PATCH] KVM: x86: Update the states size cpuid even if XCR0/IA32_XSS is reset | From | Like Xu <> |
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On 19/1/2022 2:30 am, Sean Christopherson wrote: > On Mon, Jan 17, 2022, Like Xu wrote: >> From: Like Xu <likexu@tencent.com> >> >> XCR0 is reset to 1 by RESET but not INIT and IA32_XSS is zeroed by >> both RESET and INIT. In both cases, the size in bytes of the XSAVE >> area containing all states enabled by XCR0 or (XCRO | IA32_XSS) >> needs to be updated. >> >> Fixes: a554d207dc46 ("KVM: X86: Processor States following Reset or INIT") >> Signed-off-by: Like Xu <likexu@tencent.com> >> --- >> arch/x86/kvm/x86.c | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index 76b4803dd3bd..5748a57e1cb7 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -11134,6 +11134,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) >> struct kvm_cpuid_entry2 *cpuid_0x1; >> unsigned long old_cr0 = kvm_read_cr0(vcpu); >> unsigned long new_cr0; >> + bool need_update_cpuid = false; >> >> /* >> * Several of the "set" flows, e.g. ->set_cr0(), read other registers >> @@ -11199,6 +11200,8 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) >> >> vcpu->arch.msr_misc_features_enables = 0; >> >> + if (vcpu->arch.xcr0 != XFEATURE_MASK_FP) >> + need_update_cpuid = true; >> vcpu->arch.xcr0 = XFEATURE_MASK_FP; >> } >> >> @@ -11216,6 +11219,8 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) >> cpuid_0x1 = kvm_find_cpuid_entry(vcpu, 1, 0); >> kvm_rdx_write(vcpu, cpuid_0x1 ? cpuid_0x1->eax : 0x600); >> >> + if (vcpu->arch.ia32_xss) >> + need_update_cpuid = true; > > This means that kvm_set_msr_common()'s handling of MSR_IA32_XSS also needs to > update kvm_update_cpuid_runtime(). And then for bnoth XCR0 and XSS, I would very > strongly prefer that use the helpers to write the values and let the helpers call
Looks good to me and let me apply it in the next version.
> kvm_update_cpuid_runtime(). Yes, that will mean kvm_update_cpuid_runtime() may be > called multiple times during INIT, but that's already true (CR4), and this isn't > exactly a fast path.
An undisclosed lazy mechanism is under analyzed for performance gains.
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 55518b7d3b96..22d4b1d15e94 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -11256,7 +11256,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) > > vcpu->arch.msr_misc_features_enables = 0; > > - vcpu->arch.xcr0 = XFEATURE_MASK_FP; > + __kvm_set_xcr(vcpu, 0, XFEATURE_MASK_FP); > } > > /* All GPRs except RDX (handled below) are zeroed on RESET/INIT. */ > @@ -11273,7 +11273,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) > cpuid_0x1 = kvm_find_cpuid_entry(vcpu, 1, 0); > kvm_rdx_write(vcpu, cpuid_0x1 ? cpuid_0x1->eax : 0x600); > > - vcpu->arch.ia32_xss = 0; > + __kvm_set_msr(vcpu, MSR_IA32_XSS, 0, true); > > static_call(kvm_x86_vcpu_reset)(vcpu, init_event); > >
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