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Date: Wed, 24 Apr 2024 00:36:18 +0300
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Subject: Re: [PATCH v14 28/22] [SQUASH] KVM: SEV: Provide support for
 SNP_EXTENDED_GUEST_REQUEST NAE event
From: "Jarkko Sakkinen" <jarkko@kernel.org>
To: "Michael Roth" <michael.roth@amd.com>, <kvm@vger.kernel.org>
References: <20240421180122.1650812-1-michael.roth@amd.com>
 <20240423162144.1780159-1-michael.roth@amd.com>
 <20240423162144.1780159-6-michael.roth@amd.com>
In-Reply-To: <20240423162144.1780159-6-michael.roth@amd.com>

On Tue Apr 23, 2024 at 7:21 PM EEST, Michael Roth wrote:
> Ensure an error is returned if a non-SNP guest attempts to issue an
> Extended Guest Request. Also add input validation for RAX/RBX.
>
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> ---
>  arch/x86/kvm/svm/sev.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 2b30b3b0eec8..ff64ed8df301 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -3297,6 +3297,11 @@ static int sev_es_validate_vmgexit(struct vcpu_svm=
 *svm)
>  			goto vmgexit_err;
>  		break;
>  	case SVM_VMGEXIT_EXT_GUEST_REQUEST:
> +		if (!sev_snp_guest(vcpu->kvm))
> +			goto vmgexit_err;
> +		if (!kvm_ghcb_rax_is_valid(svm) ||
> +		    !kvm_ghcb_rbx_is_valid(svm))
> +			goto vmgexit_err;

Hmm... maybe I'm ignoring something but why this is not just:

	if (!sev_snp_guest(vcpu->kvm) ||
	    !kvm_ghcb_rax_is_valid(svm) ||
	    !kvm_ghcb_rbx_is_valid(svm)))

since they branch to the same location.

BR, Jarkko