linux-kernel - Re: [PATCH] KVM: SEV: Fix uninitialized firmware error code

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Date: Wed, 15 May 2024 15:02:25 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Michael Roth <michael.roth@....com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Paolo Bonzini <pbonzini@...hat.com>, linux-coco@...ts.linux.dev,
	Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH] KVM: SEV: Fix uninitialized firmware error code

On Mon, May 13, 2024 at 12:27:04PM -0500, Michael Roth wrote:
> The current code triggers a clang warning due to passing back an
> uninitialized firmware return code in cases where an attestation request
> is aborted before getting sent to userspace. Since firmware has not been
> involved at this point the appropriate value is 0.
> 
> Reported-by: Nathan Chancellor <nathan@...nel.org>
> Closes: https://lore.kernel.org/kvm/20240513151920.GA3061950@thelio-3990X/
> Fixes: 32fde9e18b3f ("KVM: SEV: Provide support for SNP_EXTENDED_GUEST_REQUEST NAE event")
> Signed-off-by: Michael Roth <michael.roth@....com>

This obviously resolves the warning:

Tested-by: Nathan Chancellor <nathan@...nel.org> # build

> ---
>  arch/x86/kvm/svm/sev.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 57c2c8025547..59c0d89a4d52 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -4048,7 +4048,6 @@ static int snp_begin_ext_guest_req(struct kvm_vcpu *vcpu)
>  	int vmm_ret = SNP_GUEST_VMM_ERR_GENERIC;
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  	unsigned long data_npages;
> -	sev_ret_code fw_err;
>  	gpa_t data_gpa;
>  
>  	if (!sev_snp_guest(vcpu->kvm))
> @@ -4075,7 +4074,7 @@ static int snp_begin_ext_guest_req(struct kvm_vcpu *vcpu)
>  	return 0; /* forward request to userspace */
>  
>  abort_request:
> -	ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, SNP_GUEST_ERR(vmm_ret, fw_err));
> +	ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, SNP_GUEST_ERR(vmm_ret, 0));
>  	return 1; /* resume guest */
>  }
>  
> -- 
> 2.25.1
>