Re: [PATCH 15/19] kvm: x86: Save and restore guest XFD_ERR properly

[Paolo Bonzini]

On 12/8/21 01:03, Yang Zhong wrote:
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -219,6 +219,11 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
>   		kvm_apic_set_version(vcpu);
>   	}
>   
> +	/* Enable saving guest XFD_ERR */
> +	best = kvm_find_cpuid_entry(vcpu, 7, 0);
> +	if (best && cpuid_entry_has(best, X86_FEATURE_AMX_TILE))
> +		vcpu->arch.guest_fpu.xfd_err = 0;
> +

This is incorrect.  Instead it should check whether leaf 0xD includes 
any dynamic features.

Paolo