linux-kernel - Re: [PATCHv3 03/14] cpu/hotplug: Add support for declaring CPU offlining not supported

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Message-ID: <20231121093105.ev77pgbssq6scugm@box.shutemov.name>
Date:   Tue, 21 Nov 2023 12:31:05 +0300
From:   "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
To:     "Huang, Kai" <kai.huang@...el.com>
Cc:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>, "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        "Nakajima, Jun" <jun.nakajima@...el.com>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Hunter, Adrian" <adrian.hunter@...el.com>,
        "thomas.lendacky@....com" <thomas.lendacky@....com>,
        "ashish.kalra@....com" <ashish.kalra@....com>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "seanjc@...gle.com" <seanjc@...gle.com>,
        "bhe@...hat.com" <bhe@...hat.com>,
        "linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>
Subject: Re: [PATCHv3 03/14] cpu/hotplug: Add support for declaring CPU
 offlining not supported

On Tue, Nov 21, 2023 at 02:15:59AM +0000, Huang, Kai wrote:
> On Wed, 2023-11-15 at 15:00 +0300, Kirill A. Shutemov wrote:
> > The ACPI MADT mailbox wakeup method doesn't allow to offline CPU after
> > it got woke up.
> > 
> > Currently offlining hotplug is prevented based on the confidential
> > computing attribute which is set for Intel TDX. But TDX is not
> > the only possible user of the wake up method. The MADT wakeup can be
> > implemented outside of a confidential computing environment. Offline
> > support is a property of the wakeup method, not the CoCo implementation.
> > 
> > Introduce cpu_hotplug_not_supported() that can be called to indicate
> > that CPU offlining should be disabled.
> 
> cpu_hotplug_not_supported() -> cpu_hotplug_disable_offlining().

Right.

> > 
> > This function is going to replace CC_ATTR_HOTPLUG_DISABLED for ACPI
> > MADT.
> 
> Is MADT too generic? MADT wakeup?

I'll replace it with "ACPI MADT wakeup method".

-- 
  Kiryl Shutsemau / Kirill A. Shutemov