linux-kernel - Re: [RFC PATCH 40/56] x86/alternative: Use sync_core_nmi

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Message-ID: <20251016185811.GH3289052@noisy.programming.kicks-ass.net>
Date: Thu, 16 Oct 2025 20:58:11 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: "Kaplan, David" <David.Kaplan@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"H . Peter Anvin" <hpa@...or.com>, Alexander Graf <graf@...zon.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 40/56] x86/alternative: Use sync_core_nmi_safe()

On Thu, Oct 16, 2025 at 06:56:41PM +0000, Kaplan, David wrote:

> > About faster, no. But MFENCE has the benefit of not causing VMEXITs and
> > also not being IRET, so I'm not opposed to you using that as an AMD
> > version of SERIALIZE for the time being.
> 
> Ok.  Btw, how long has Intel supported SERIALIZE?

I'm not sure.. its fairly new, so

> Do we even need a 'mov-cr2' version of sync_core or could we say that
> dynamic mitigations requires a CPU capable of either a serializing
> MFENCE or SERIALIZE.

don't think we can get away with that, alas.