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References: <20221104230040.2346862-1-dionnaglaze@google.com> <20221104230040.2346862-3-dionnaglaze@google.com>
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From:   Peter Gonda <pgonda@google.com>
Date:   Fri, 4 Nov 2022 19:33:02 -0600
Message-ID: <CAMkAt6oCnHWbDBnrszw3rSBHmLj8Mqou0m6Sjt0Ov67QNd5kHg@mail.gmail.com>
Subject: Re: [PATCH v8 2/4] x86/sev: Change snp_guest_issue_request's fw_err
To:     Dionna Glaze <dionnaglaze@google.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        Tom Lendacky <Thomas.Lendacky@amd.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Joerg Roedel <jroedel@suse.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Venu Busireddy <venu.busireddy@oracle.com>,
        Michael Roth <michael.roth@amd.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Michael Sterritt <sterritt@google.com>
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On Fri, Nov 4, 2022 at 5:01 PM Dionna Glaze <dionnaglaze@google.com> 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@amd.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Joerg Roedel <jroedel@suse.de>
> Cc: Peter Gonda <pgonda@google.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Venu Busireddy <venu.busireddy@oracle.com>
> Cc: Michael Roth <michael.roth@amd.com>
> Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
> Cc: Michael Sterritt <sterritt@google.com>
>
> Fixes: d5af44dde546 ("x86/sev: Provide support for SNP guest request NAEs")
> Signed-off-by: Dionna Glaze <dionnaglaze@google.com>

Reviewed-by: Peter Gonda <pgonda@google.com