linux-kernel - Re: [PATCH 02/10] KVM: x86: nSVM: Add VALID_GPAT flag to kvm_svm_nested_state

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Message-ID: <aWgJv154AfkrvqfQ@google.com>
Date: Wed, 14 Jan 2026 13:25:19 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Jim Mattson <jmattson@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, Shuah Khan <shuah@...nel.org>, Joerg Roedel <joro@...tes.org>, 
	Avi Kivity <avi@...hat.com>, Alexander Graf <agraf@...e.de>, 
	"Radim Krčmář" <rkrcmar@...hat.com>, David Hildenbrand <david@...nel.org>, Cathy Avery <cavery@...hat.com>, 
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 02/10] KVM: x86: nSVM: Add VALID_GPAT flag to kvm_svm_nested_state_hdr

On Mon, Jan 12, 2026, Jim Mattson wrote:
>  /* for KVM_CAP_NESTED_STATE */
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index a0e5bf1aba52..ed24e08d2d21 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -1769,6 +1769,7 @@ static int svm_get_nested_state(struct kvm_vcpu *vcpu,
>  	/* First fill in the header and copy it out.  */
>  	if (is_guest_mode(vcpu)) {
>  		kvm_state.hdr.svm.vmcb_pa = svm->nested.vmcb12_gpa;
> +		kvm_state.hdr.svm.flags = KVM_STATE_SVM_VALID_GPAT;

Assuming this survives to v2, make this:

		kvm_state.hdr.svm.flags |= KVM_STATE_SVM_VALID_GPAT;

both to communicate that there's no pre-existing bug where KVM doesn't initialize
flags, and so that there's less risk of clobbering others flags, e.g. if a new
flag is added in the future and is set before this point.

>  		kvm_state.size += KVM_STATE_NESTED_SVM_VMCB_SIZE;
>  		kvm_state.flags |= KVM_STATE_NESTED_GUEST_MODE;
>  
> -- 
> 2.52.0.457.g6b5491de43-goog
>