linux-kernel - Re: [PATCH] KVM: x86: Restore update of required xstate size in guest's CPUID

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Message-ID: <bec6f18e-510e-c5bd-b5b4-d9e188153bc7@redhat.com>
Date:   Sat, 9 May 2020 14:51:28 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>
Subject: Re: [PATCH] KVM: x86: Restore update of required xstate size in
 guest's CPUID

On 09/05/20 01:37, Sean Christopherson wrote:
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 35845704cf57a..cd708b0b460a0 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -84,11 +84,13 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
>  				   kvm_read_cr4_bits(vcpu, X86_CR4_PKE));
>  
>  	best = kvm_find_cpuid_entry(vcpu, 0xD, 0);
> -	if (!best)
> +	if (!best) {
>  		vcpu->arch.guest_supported_xcr0 = 0;
> -	else
> +	} else {
>  		vcpu->arch.guest_supported_xcr0 =
>  			(best->eax | ((u64)best->edx << 32)) & supported_xcr0;
> +		best->ebx = xstate_required_size(vcpu->arch.xcr0, false);
> +	}
>  
>  	best = kvm_find_cpuid_entry(vcpu, 0xD, 1);
>  	if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
> -- 2.26.0

Ugh, I'll write a testcase as penance.  Squashed, thanks.

Paolo