linux-kernel - Re: [PATCHv10 03/18] cpu/hotplug: Add support for declaring CPU offlining not supported

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Message-ID: <20240418143709.GJZiEwFejGQY3jiwsp@fat_crate.local>
Date: Thu, 18 Apr 2024 16:37:09 +0200
From: Borislav Petkov <bp@...en8.de>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
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 03/18] cpu/hotplug: Add support for declaring CPU
 offlining not supported

On Tue, Apr 09, 2024 at 02:29:55PM +0300, Kirill A. Shutemov wrote:
> +/* Declare CPU offlining not supported */
> +void cpu_hotplug_disable_offlining(void)
> +{
> +	cpu_maps_update_begin();

"/*
 * The following two APIs (cpu_maps_update_begin/done) must be used when
 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
 */
void cpu_maps_update_begin(void)
.."

> +	cpu_hotplug_offline_disabled = true;

but this doesn't do that here.

Are we doing a one-off here for that variable or what?

> +	cpu_maps_update_done();

-- 
Regards/Gruss,
    Boris.

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