linux-kernel - Re: [PATCH v3 2/2] x86/sev: Get the AP jump table address from secrets page

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Date:   Fri, 22 Apr 2022 10:15:08 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Michael Roth <michael.roth@....com>, linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Kees Cook <keescook@...omium.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Venu Busireddy <venu.busireddy@...cle.com>,
        Joerg Roedel <jroedel@...e.de>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v3 2/2] x86/sev: Get the AP jump table address from
 secrets page

On 4/22/22 08:56, Michael Roth wrote:
> From: Brijesh Singh <brijesh.singh@....com>
> 
> The GHCB specification section 2.7 states that when SEV-SNP is enabled,
> a hypervisor must provide the AP jump table physical address through

I missed this on the first version. It's not the hypervisor, but the guest 
BIOS that directly provides the AP jump table physical address, in our 
case OVMF sets the address in the SNP secrets page. This allows 
communication between UEFI/BIOS and OS without hypervisor involvement.

> the SNP secrets pages.
> 
> Fixes: 0afb6b660a6b ("x86/sev: Use SEV-SNP AP creation to start secondary CPUs")
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> [ mroth: improve error handling when ioremap()/memremap() return NULL ]
> [ mroth: don't mix function calls with declarations ]
> [ mroth: add missing __init ]
> Signed-off-by: Michael Roth <michael.roth@....com>

With the commit message change:

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