From: Pavel Machek <pavel@ucw.cz>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: linux-pm@vger.kernel.org, x86@kernel.org,
Chen Yu <yu.c.chen@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>, Borislav Petkov <bp@suse.de>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Len Brown <lenb@kernel.org>,
linux-kernel@vger.kernel.org, James Morse <james.morse@arm.com>
Subject: Re: [PATCH v2] x86 / hibernate: Use hlt_play_dead() when resuming from hibernation
Date: Thu, 28 Jul 2016 21:34:02 +0200 [thread overview]
Message-ID: <20160728193402.GD11657@amd> (raw)
In-Reply-To: <2496371.r57m45JVIP@vostro.rjw.lan>
On Thu 2016-07-14 03:55:23, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> On Intel hardware, native_play_dead() uses mwait_play_dead() by
> default and only falls back to the other methods if that fails.
> That also happens during resume from hibernation, when the restore
> (boot) kernel runs disable_nonboot_cpus() to take all of the CPUs
> except for the boot one offline.
>
> However, that is problematic, because the address passed to
> __monitor() in mwait_play_dead() is likely to be written to in the
> last phase of hibernate image restoration and that causes the "dead"
> CPU to start executing instructions again. Unfortunately, the page
> containing the address in that CPU's instruction pointer may not be
> valid any more at that point.
>
> First, that page may have been overwritten with image kernel memory
> contents already, so the instructions the CPU attempts to execute may
> simply be invalid. Second, the page tables previously used by that
> CPU may have been overwritten by image kernel memory contents, so the
> address in its instruction pointer is impossible to resolve then.
>
> A report from Varun Koyyalagunta and investigation carried out by
> Chen Yu show that the latter sometimes happens in practice.
>
> To prevent it from happening, temporarily change the smp_ops.play_dead
> pointer during resume from hibernation so that it points to a special
> "play dead" routine which uses hlt_play_dead() and avoids the
> inadvertent "revivals" of "dead" CPUs this way.
>
> A slightly unpleasant consequence of this change is that if the
> system is hibernated with one or more CPUs offline, it will generally
> draw more power after resume than it did before hibernation, because
> the physical state entered by CPUs via hlt_play_dead() is higher-power
> than the mwait_play_dead() one in the majority of cases. It is
> possible to work around this, but it is unclear how much of a problem
> that's going to be in practice, so the workaround will be implemented
> later if it turns out to be necessary.
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=106371
> Reported-by: Varun Koyyalagunta <cpudebug@centtech.com>
> Original-by: Chen Yu <yu.c.chen@intel.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
prev parent reply other threads:[~2016-07-28 19:34 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-28 9:16 [PATCH][RFC v3] x86, hotplug: Use hlt instead of mwait if invoked from disable_nonboot_cpus Chen Yu
2016-07-07 0:33 ` Rafael J. Wysocki
2016-07-07 2:50 ` Chen, Yu C
2016-07-07 16:03 ` James Morse
2016-07-07 8:38 ` James Morse
2016-07-07 12:25 ` Rafael J. Wysocki
2016-07-10 1:49 ` [PATCH] x86 / hibernate: Use hlt_play_dead() when resuming from hibernation Rafael J. Wysocki
2016-07-13 9:56 ` Pavel Machek
2016-07-13 10:29 ` Chen Yu
2016-07-13 12:01 ` Rafael J. Wysocki
2016-07-13 12:41 ` Rafael J. Wysocki
2016-07-28 19:33 ` Pavel Machek
2016-07-14 1:55 ` [PATCH v2] " Rafael J. Wysocki
2016-07-14 8:57 ` Ingo Molnar
2016-07-28 19:34 ` Pavel Machek [this message]
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