linux-kernel - Re: [PATCH][RFC v3] x86, hotplug: Use hlt instead of mwait if invoked from disable_nonboot

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Date:	Thu, 07 Jul 2016 09:38:14 +0100
From:	James Morse <james.morse@....com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Chen Yu <yu.c.chen@...el.com>
CC:	linux-pm@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Pavel Machek <pavel@....cz>,
	Borislav Petkov <bp@...e.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Len Brown <lenb@...nel.org>,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][RFC v3] x86, hotplug: Use hlt instead of mwait if invoked
 from disable_nonboot_cpus

Hi Rafael,

On 07/07/16 01:33, Rafael J. Wysocki wrote:
> Below is my sort of version of this (untested) and I did it this way, because
> the issue is specific to resume from hibernation (the workaround need not be
> applied anywhere else) and the hibernate_resume_nonboot_cpu_disable() thing may
> be useful to arm64 too if I'm not mistaken (James?).

Yes, we will always need to do something extra (based on data in the
arch_hibernation_header) to resume if CPU0 was offline, or kexec meant we no
longer know which CPU the firmware will boot us on.


> Actually, if arm64 uses it too, the __weak implementation can be dropped,
> because it will be possible to make it depend on ARCH_HIBERNATION_HEADER
> (x86 and arm64 are the only users of that).

Heh, I avoided that as it felt too much like a hack!



Thanks,

James