linux-kernel - Re: [PATCH v4 2/4] x86/sev: Change snp_guest_issue_request's fw

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Date:   Fri, 28 Oct 2022 09:45:09 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Dionna Glaze <dionnaglaze@...gle.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Joerg Roedel <jroedel@...e.de>,
        Peter Gonda <pgonda@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH v4 2/4] x86/sev: Change snp_guest_issue_request's fw_err

On 10/24/22 17:46, Dionna Glaze wrote:
> The GHCB specification declares that the firmware error value for a
> guest request will be stored in the lower 32 bits of EXIT_INFO_2.
> The upper 32 bits are for the VMM's own error code. The fw_err argument
> is thus a misnomer, and callers will need access to all 64 bits.
> 
> The type of unsigned long also causes problems, since sw_exit_info2 is
> u64 (unsigned long long) vs the argument's previous unsigned long*.
> The signature change requires the follow-up change to
> drivers/virt/coco/sev-guest to use the new expected type in order to
> compile.
> 
> The firmware might not even be called, so we bookend the call with the
> no firmware call error and clearing the error.
> 
> Cc: Tom Lendacky <Thomas.Lendacky@....com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Joerg Roedel <jroedel@...e.de>
> Cc: Peter Gonda <pgonda@...gle.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> 
> Fixes: d5af44dde546 ("x86/sev: Provide support for SNP guest request NAEs")
> Signed-off-by: Dionna Glaze <dionnaglaze@...gle.com>

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

> ---
>   arch/x86/include/asm/sev.h |  4 ++--
>   arch/x86/kernel/sev.c      | 10 ++++++----
>   2 files changed, 8 insertions(+), 6 deletions(-)
>