linux-kernel - Re: [PATCH v5 1/2] KVM: SVM: Convert plain error code numbers to defines

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Message-ID: <Z75EHspU4ZPcqw0U@google.com>
Date: Tue, 25 Feb 2025 14:28:46 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Melody Wang <huibo.wang@....com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, KVM <kvm@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, Tom Lendacky <thomas.lendacky@....com>, 
	Paluri PavanKumar <pavankumar.paluri@....com>, Pavan Kumar Paluri <papaluri@....com>
Subject: Re: [PATCH v5 1/2] KVM: SVM: Convert plain error code numbers to defines

On Tue, Feb 25, 2025, Melody Wang wrote:
> Convert VMGEXIT SW_EXITINFO1 codes from plain numbers to proper defines.
> 
> No functionality changed.
> 
> Signed-off-by: Melody Wang <huibo.wang@....com>
> Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
> Reviewed-by: Pavan Kumar Paluri <papaluri@....com>
> ---
>  arch/x86/include/asm/sev-common.h |  8 ++++++++
>  arch/x86/kvm/svm/sev.c            | 12 ++++++------
>  arch/x86/kvm/svm/svm.c            |  2 +-
>  3 files changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
> index dcbccdb280f9..3aca97d22cdc 100644
> --- a/arch/x86/include/asm/sev-common.h
> +++ b/arch/x86/include/asm/sev-common.h
> @@ -211,6 +211,14 @@ struct snp_psc_desc {
>  
>  #define GHCB_RESP_CODE(v)		((v) & GHCB_MSR_INFO_MASK)
>  
> +/*
> + * Error codes of the GHCB SW_EXITINFO1 related to GHCB input that can be

The use of "Error codes" is confusing due to a psuedo-conflict with the below
comment for the "Error codes" for malformed input.

On that topic, the comment for _those_ error codes is a bad example, and shouldn't
be used as the basis for copy+paste.  Most notably, it doesn't explicitly state
that the values are *defined* by the GHCB.

> + * communicated back to the guest
> + */
> +#define GHCB_HV_RESP_NO_ACTION		0
> +#define GHCB_HV_RESP_ISSUE_EXCEPTION	1
> +#define GHCB_HV_RESP_MALFORMED_INPUT	2
> +
>  /*
>   * Error codes related to GHCB input that can be communicated back to the guest
>   * by setting the lower 32-bits of the GHCB SW_EXITINFO1 field to 2.

Now that GHCB_HV_RESP_MALFORMED_INPUT is properly defined, this comment can refer
to "malformed input (see above)" instead of open coding '2'.