Received-SPF: pass (google.com: domain of linux-kernel+bounces-96955-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Precedence: bulk
MIME-Version: 1.0
References: <CAGdbjmK9WoOQSbKUvcTdLJDW-RB=qe2tHFDZ-MeD266xZOxh7w@mail.gmail.com>
 <20240222202404.36206-1-kevinloughlin@google.com> <CAMj1kXFsX1HZ3=x1cjN0-7i5EV9LXkSrAW22dc1wERUaTdAMaA@mail.gmail.com>
 <20240308110043.GEZerv21Qj10Q7-8p5@fat_crate.local>
In-Reply-To: <20240308110043.GEZerv21Qj10Q7-8p5@fat_crate.local>
From: Ard Biesheuvel <ardb@kernel.org>
Date: Fri, 8 Mar 2024 12:44:31 +0100
Message-ID: <CAMj1kXFe48dUtNkCDG0PcmeGhYfvr5HJ8sucuNGwCJ1XDKw03Q@mail.gmail.com>
Subject: Re: [PATCH v2] x86/kernel: skip ROM range scans and validation for
 SEV-SNP guests
To: Borislav Petkov <bp@alien8.de>
Cc: Kevin Loughlin <kevinloughlin@google.com>, acdunlap@google.com, 
	alexander.shishkin@linux.intel.com, andrisaar@google.com, bhe@redhat.com, 
	brijesh.singh@amd.com, dave.hansen@linux.intel.com, dionnaglaze@google.com, 
	grobler@google.com, hpa@zytor.com, jacobhxu@google.com, jpoimboe@kernel.org, 
	kai.huang@intel.com, linux-kernel@vger.kernel.org, michael.roth@amd.com, 
	mingo@redhat.com, peterz@infradead.org, pgonda@google.com, 
	ross.lagerwall@citrix.com, sidtelang@google.com, tglx@linutronix.de, 
	thomas.lendacky@amd.com, x86@kernel.org, ytcoode@gmail.com
Content-Type: text/plain; charset="UTF-8"

On Fri, 8 Mar 2024 at 12:01, Borislav Petkov <bp@alien8.de> wrote:
>
> On Fri, Mar 08, 2024 at 11:30:50AM +0100, Ard Biesheuvel wrote:
> > Agree with the analysis and the conclusion. However, this will need to
> > be split into generic and x86 specific changes, given that the DMI
> > code is shared between all architectures, and explicitly checking for
> > SEV-SNP support in generic code is not appropriate.
> >
> > So what we will need is:
>
> I was actually thinking of:
>
>         x86_init.resources.probe_roms = snp_probe_roms;
>
> and snp_probe_roms() is an empty stub.
>
> Problem solved without ugly sprinkling of checks everywhere.
>

Indeed. Setting the override could be done in
init_hypervisor_platform(), which is called right before from
setup_arch().