linux-kernel - Re: [PATCH v1] x86/smp: Set up exception handling before cr4

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Message-ID: <cc4eae31-e4fd-4052-939f-57b203c53927@intel.com>
Date: Mon, 9 Feb 2026 07:14:38 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Xin Li <xin@...or.com>, Sohil Mehta <sohil.mehta@...el.com>
Cc: linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
 bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
 peterz@...radead.org, andrew.cooper3@...rix.com, nikunj@....com,
 thomas.lendacky@....com, seanjc@...gle.com, stable@...r.kernel.org
Subject: Re: [PATCH v1] x86/smp: Set up exception handling before cr4_init()

On 2/9/26 00:16, Xin Li wrote:
> I’m not sure if Dave also wants to make BSP/AP boot code symmetric
> at the same time 😉

It's perfectly fine to do things one bit at a time. In this case,
cr4_init() is does two different things underneath the covers depending
on the state of CR pinning. If CR pinning as a feature is kicked out
influencing the early CPU boot code at _all_, then it certainly helps
the goal if making the AP/BSP code more symmetric.

So I very much prefer doing things one bit at a time, if we can.