linux-kernel - Re: [PATCH v6 10/22] x86/boot: Drop redundant RMPADJUST in SEV SVSM presence check

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Message-ID: <20250811063026.GMaJmOAoo-PhdXcLZX@fat_crate.local>
Date: Mon, 11 Aug 2025 08:30:26 +0200
From: Borislav Petkov <bp@...en8.de>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org, x86@...nel.org,
	Ard Biesheuvel <ardb@...nel.org>, Ingo Molnar <mingo@...nel.org>,
	Kevin Loughlin <kevinloughlin@...gle.com>,
	Tom Lendacky <thomas.lendacky@....com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Nikunj A Dadhania <nikunj@....com>
Subject: Re: [PATCH v6 10/22] x86/boot: Drop redundant RMPADJUST in SEV SVSM
 presence check

On Tue, Jul 22, 2025 at 09:27:19AM +0200, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@...nel.org>
> 
> snp_vmpl will be assigned a non-zero value when executing at a VMPL
> other than 0, and this is inferred from a call to RMPADJUST, which only
> works when running at VMPL0.
> 
> This means that testing snp_vmpl is sufficient, and there is no need to
> perform the same check again.

Remind me again pls: the startup code is going to be executed unconditionally,
even by the decompressor, right?

Because if it is an alternative path, we can't do the below.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette