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

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Message-ID: <svpuqhoglv7s2wtu754i4oicowueen47vq6eobjbznsromb4m3@4h7vy346n4ak>
Date: Wed, 24 Apr 2024 17:35:46 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Borislav Petkov <bp@...en8.de>
Cc: 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 03:50:52PM +0200, Borislav Petkov wrote:
> On Wed, Apr 24, 2024 at 11:38:42AM +0300, Kirill A. Shutemov wrote:
> > It was wrong from beginning. If ACPI MADT wake up method is used on the
> > platform, we cannot handle offline, regardless if it is TDX or not.
> 
> Sounds to me like this fact should be a prominent part of the commit
> message and these 1-4 patches should be carved out as a separate set
> fixing that ACPI MADT thing and I should take them separately now...?
> 
> 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.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov