RE: [PATCH v4 18/21] kvm: x86: Add support for getting/setting expanded xstate buffer

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> From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Sent: Wednesday, January 5, 2022 4:46 AM
> 
> On 1/4/22 20:46, Sean Christopherson wrote:
> > On Wed, Dec 29, 2021, Yang Zhong wrote:
> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> >> index bdf89c28d2ce..76e1941db223 100644
> >> --- a/arch/x86/kvm/x86.c
> >> +++ b/arch/x86/kvm/x86.c
> >> @@ -4296,6 +4296,11 @@ int kvm_vm_ioctl_check_extension(struct kvm
> *kvm, long ext)
> >>   		else
> >>   			r = 0;
> >>   		break;
> >> +	case KVM_CAP_XSAVE2:
> >> +		r = kvm->vcpus[0]->arch.guest_fpu.uabi_size;
> >
> > a) This does not compile against kvm/queue.
> >
> >     arch/x86/kvm/x86.c: In function ‘kvm_vm_ioctl_check_extension’:
> >     arch/x86/kvm/x86.c:4317:24: error: ‘struct kvm’ has no member named
> ‘vcpus’
> >      4317 |                 r = kvm->vcpus[0]->arch.guest_fpu.uabi_size;
> >
> > b) vcpu0 is not guaranteed to be non-NULL at this point.
> 
> Yang, you can post an incremental patch for this.  You can use the
> highest bit of the guest-permitted xcr0 (i.e. the OR of KVM's supported
> XCR0 an the guest-permitted dynamic features) and pass it to cpuid(0xD).
> 

Will do, except one correction that 'OR' should be 'AND' here. 😊

Thanks
Kevin




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