linux-kernel - Re: [PATCH V3] KVM: SEV: Update SEV-ES shutdown intercepts with more metadata

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Date:   Thu, 7 Sep 2023 16:56:46 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Peter Gonda <pgonda@...gle.com>, kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3] KVM: SEV: Update SEV-ES shutdown intercepts with more
 metadata

On 9/7/23 11:24, Peter Gonda wrote:
> Currently if an SEV-ES VM shuts down userspace sees KVM_RUN struct with
> only the INVALID_ARGUMENT. This is a very limited amount of information
> to debug the situation. Instead KVM can return a
> KVM_EXIT_SHUTDOWN to alert userspace the VM is shutting down and
> is not usable any further.
> 
> Signed-off-by: Peter Gonda <pgonda@...gle.com>
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Suggested-by: Tom Lendacky <thomas.lendacky@....com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Sean Christopherson <seanjc@...gle.com>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: x86@...nel.org
> Cc: kvm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>   arch/x86/kvm/svm/svm.c | 15 +++++++--------
>   1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 956726d867aa..114afc897465 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -2127,12 +2127,6 @@ static int shutdown_interception(struct kvm_vcpu *vcpu)
>   	struct kvm_run *kvm_run = vcpu->run;
>   	struct vcpu_svm *svm = to_svm(vcpu);
>   
> -	/*
> -	 * The VM save area has already been encrypted so it
> -	 * cannot be reinitialized - just terminate.
> -	 */
> -	if (sev_es_guest(vcpu->kvm))
> -		return -EINVAL;
>   
>   	/*
>   	 * VMCB is undefined after a SHUTDOWN intercept.  INIT the vCPU to put
> @@ -2141,9 +2135,14 @@ static int shutdown_interception(struct kvm_vcpu *vcpu)
>   	 * userspace.  At a platform view, INIT is acceptable behavior as
>   	 * there exist bare metal platforms that automatically INIT the CPU
>   	 * in response to shutdown.
> +	 *
> +	 * The VM save area for SEV-ES guests has already been encrypted so it
> +	 * cannot be reinitialized, i.e. synthesizing INIT is futile.
>   	 */
> -	clear_page(svm->vmcb);
> -	kvm_vcpu_reset(vcpu, true);
> +	if (!sev_es_guest(vcpu->kvm)) {
> +		clear_page(svm->vmcb);
> +		kvm_vcpu_reset(vcpu, true);
> +	}
>   
>   	kvm_run->exit_reason = KVM_EXIT_SHUTDOWN;
>   	return 0;