linux-kernel - Re: [RFC PATCH 1/5] x86/kexec: Do unconditional WBINVD for bare-metal in stop_this

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Message-ID: <c2b4886c449f96a423b2c0f0ec978550c16ef58e.camel@intel.com>
Date: Wed, 19 Mar 2025 21:42:57 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"Hansen, Dave" <dave.hansen@...el.com>, "Edgecombe, Rick P"
	<rick.p.edgecombe@...el.com>
CC: "Williams, Dan J" <dan.j.williams@...el.com>, "ashish.kalra@....com"
	<ashish.kalra@....com>, "dyoung@...hat.com" <dyoung@...hat.com>,
	"thomas.lendacky@....com" <thomas.lendacky@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Chatre,
 Reinette" <reinette.chatre@...el.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "pbonzini@...hat.com" <pbonzini@...hat.com>,
	"bhe@...hat.com" <bhe@...hat.com>, "Yamahata, Isaku"
	<isaku.yamahata@...el.com>, "nik.borisov@...e.com" <nik.borisov@...e.com>,
	"mingo@...hat.com" <mingo@...hat.com>, "dwmw@...zon.co.uk"
	<dwmw@...zon.co.uk>, "hpa@...or.com" <hpa@...or.com>, "sagis@...gle.com"
	<sagis@...gle.com>, "peterz@...radead.org" <peterz@...radead.org>,
	"bp@...en8.de" <bp@...en8.de>, "tglx@...utronix.de" <tglx@...utronix.de>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [RFC PATCH 1/5] x86/kexec: Do unconditional WBINVD for bare-metal
 in stop_this_cpu()

On Wed, 2025-03-19 at 09:41 -0700, Hansen, Dave wrote:
> As for kexec vs. PAT memtypes, there are only even theoretical issues on
> old hardware.  They _theoretically_ need a WBINVD at kexec. But there
> might be enough other things happening during kexec (including other
> WBINVD's) to keep us from getting bitten in practice.

From this perspective, I think it makes sense to do WBINVD for bare-metal
machines anyway?  Perhaps I can mention this in the changelog?