linux-kernel - Re: [PATCHv7 16/16] x86/acpi: Add support for CPU offlining for ACPI MADT wakeup method

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Message-ID: <87jzmvcw0f.ffs@tglx>
Date: Fri, 23 Feb 2024 11:31:12 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Ingo Molnar
 <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
 <dave.hansen@...ux.intel.com>, x86@...nel.org
Cc: "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, "Kirill A. Shutemov"
 <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCHv7 16/16] x86/acpi: Add support for CPU offlining for
 ACPI MADT wakeup method

On Mon, Feb 12 2024 at 12:44, Kirill A. Shutemov wrote:
> MADT Multiprocessor Wakeup structure version 1 brings support of CPU
> offlining: BIOS provides a reset vector where the CPU has to jump to
> for offlining itself. The new TEST mailbox command can be used to test
> whether the CPU offlined itself which means the BIOS has control over
> the CPU and can online it again via the ACPI MADT wakeup method.
>
> Add CPU offling support for the ACPI MADT wakeup method by implementing
> custom cpu_die(), play_dead() and stop_this_cpu() SMP operations.
>
> CPU offlining makes is possible to hand over secondary CPUs over kexec,
> not limiting the second kernel to a single CPU.
>
> The change conforms to the approved ACPI spec change proposal. See the
> Link.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Link: https://lore.kernel.org/all/13356251.uLZWGnKmhe@kreacher
> Acked-by: Kai Huang <kai.huang@...el.com>
> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>