linux-kernel - Re: [PATCH v2] x86/kernel: skip ROM range scans and validation for SEV-SNP guests

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Message-ID: <CAMj1kXFe48dUtNkCDG0PcmeGhYfvr5HJ8sucuNGwCJ1XDKw03Q@mail.gmail.com>
Date: Fri, 8 Mar 2024 12:44:31 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: Kevin Loughlin <kevinloughlin@...gle.com>, acdunlap@...gle.com, 
	alexander.shishkin@...ux.intel.com, andrisaar@...gle.com, bhe@...hat.com, 
	brijesh.singh@....com, dave.hansen@...ux.intel.com, dionnaglaze@...gle.com, 
	grobler@...gle.com, hpa@...or.com, jacobhxu@...gle.com, jpoimboe@...nel.org, 
	kai.huang@...el.com, linux-kernel@...r.kernel.org, michael.roth@....com, 
	mingo@...hat.com, peterz@...radead.org, pgonda@...gle.com, 
	ross.lagerwall@...rix.com, sidtelang@...gle.com, tglx@...utronix.de, 
	thomas.lendacky@....com, x86@...nel.org, ytcoode@...il.com
Subject: Re: [PATCH v2] x86/kernel: skip ROM range scans and validation for
 SEV-SNP guests

On Fri, 8 Mar 2024 at 12:01, Borislav Petkov <bp@...en8.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().