linux-kernel - Re: [PATCH v7 10/22] x86/boot: Drop redundant RMPADJUST in SEV SVSM presence check

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Message-ID: <20250902120221.GEaLbczaZ1RPY7dGKH@fat_crate.local>
Date: Tue, 2 Sep 2025 14:02:21 +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 v7 10/22] x86/boot: Drop redundant RMPADJUST in SEV SVSM
 presence check

On Thu, Aug 28, 2025 at 12:22:13PM +0200, Ard Biesheuvel wrote:
> -		/*
> -		 * Running at VMPL0 is not required if an SVSM is present and the hypervisor
> -		 * supports the required SVSM GHCB events.
> -		 */
> -		if (ret &&
> -		    !(snp_vmpl && (hv_features & GHCB_HV_FT_SNP_MULTI_VMPL)))
> +		if (snp_vmpl > 0 && !(hv_features & GHCB_HV_FT_SNP_MULTI_VMPL))

Yeah, it is unsigned:

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 973ca206794a..808211b09424 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -415,7 +415,7 @@ void sev_enable(struct boot_params *bp)
 		 * Running at VMPL0 is required unless an SVSM is present and
 		 * the hypervisor supports the required SVSM GHCB events.
 		 */
-		if (snp_vmpl > 0 && !(hv_features & GHCB_HV_FT_SNP_MULTI_VMPL))
+		if (snp_vmpl && !(hv_features & GHCB_HV_FT_SNP_MULTI_VMPL))
 			sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_NOT_VMPL0);
 	}
 
-- 
Regards/Gruss,
    Boris.

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