linux-kernel - Re: [PATCH] x86/cpufeatures: Correct LKGS feature flag description

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Message-ID: <20251015154911.GCaO_Cd0XNyE8bi5Db@fat_crate.local>
Date: Wed, 15 Oct 2025 17:49:11 +0200
From: Borislav Petkov <bp@...en8.de>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: Xin Li <xin@...or.com>, Borislav Petkov <bp@...nel.org>,
	Xin Li <xin3.li@...el.com>, X86 ML <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/cpufeatures: Correct LKGS feature flag description

On Wed, Oct 15, 2025 at 08:44:55AM -0700, H. Peter Anvin wrote:
> >> Except that that is also wrong, because that's not all of what the instruction does. "Load user space GS" is really what it does, despite the initiate historical naming.
> >> 
> >
> >Do you mean the load of GS attributes by LKGS is still missing?
> 
> Yes. It's really a modified MOV GS,... instruction that loads the base, limit, selector, and attributes; it just loads the base into a different place.

Ok, "Load user space GS base" it is. Considering how you can't load any other
GS.base due to it GPing for CPL > 0.

-- 
Regards/Gruss,
    Boris.

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