linux-kernel - Re: [PATCHv10 04/18] cpu/hotplug, x86/acpi: Disable CPU offlining for ACPI MADT wakeup

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Date: Wed, 24 Apr 2024 16:51:22 +0200
From: Borislav Petkov <bp@...en8.de>
To: Dave Hansen <dave.hansen@...el.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	Elena Reshetova <elena.reshetova@...el.com>,
	Jun Nakajima <jun.nakajima@...el.com>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Tom Lendacky <thomas.lendacky@....com>,
	"Kalra, Ashish" <ashish.kalra@....com>,
	Sean Christopherson <seanjc@...gle.com>,
	"Huang, Kai" <kai.huang@...el.com>, Baoquan He <bhe@...hat.com>,
	kexec@...ts.infradead.org, linux-coco@...ts.linux.dev,
	linux-kernel@...r.kernel.org, Tao Liu <ltao@...hat.com>
Subject: Re: [PATCHv10 04/18] cpu/hotplug, x86/acpi: Disable CPU offlining
 for ACPI MADT wakeup

On Wed, Apr 24, 2024 at 07:40:26AM -0700, Dave Hansen wrote:
> On 4/24/24 07:35, Kirill A. Shutemov wrote:
> >> Also, does this need to go to stable although it is kinda big for
> >> stable. If stable, do we need a smaller fix first which is backportable?
> > Correct me, if I am wrong, but I believe TDX guest is the only user of
> > ACPI MADT wake up method. At least it was added into kernel for TDX guest.
> > So it wouldn't fix anything user-visible. It might affect a future
> > platform that uses this wake up method, but it is a guessing game.
> 
> Yeah, the MADT wakeup is pretty funky, highly TDX specific, and not in
> use or planned to be _put_ into use anywhere else.

Then please make sure all that info is in the commit messages in the
next revision. Because as they are now, they're not even beginning to
explain what exactly is this fixing. /me thinking that this is some
generic fix needed in stable is case-in-point.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette