linux-kernel - Re: [PATCH] [v2] PM / hibernate: Fix hibernation panic caused by inconsistent e820 map

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Message-ID: <20150917054027.GC6665@amd>
Date:	Thu, 17 Sep 2015 07:40:27 +0200
From:	Pavel Machek <pavel@....cz>
To:	Chen Yu <yu.c.chen@...el.com>
Cc:	rjw@...ysocki.net, len.brown@...el.com, mingo@...hat.com,
	yinghai@...nel.org, joeyli.kernel@...il.com,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [v2] PM / hibernate: Fix hibernation panic caused by
 inconsistent e820 map

Hi!

> PM: Image mismatch: memory size
> 
> This is also because BIOS provides different e820 memory map before/after
> hibernation, and linux regards it as invalid process and refuses to
> resume, in order to protect against data corruption. However,
> this check might be too strict, consider the following scenario:

Well... yes, the check is strict, but why is BIOS doing that? Can you
fix it instead?

> The hibernating system has a smaller memory capacity than
> the resuming system, and the former memory region is a subset of the
> latter, it should be allowed to resume. Here is a case for this
> situation:
> 
> before hibernation:
> 
> BIOS-e820: [mem 0x0000000020200000-0x0000000077517fff] usable
> BIOS-e820: [mem 0x0000000077518000-0x0000000077567fff] reserved
> Memory: 3871356K/4058428K available (7595K kernel code, 1202K rwdata,
> 3492K rodata, 1400K init, 1308K bss, 187072K reserved, 0K cma-reserved)
> 
> after hibernation:
> BIOS-e820: [mem 0x0000000020200000-0x000000007753ffff] usable
> BIOS-e820: [mem 0x0000000077540000-0x0000000077567fff] reserved
> Memory: 3871516K/4058588K available (7595K kernel code, 1202K rwdata,
> 3492K rodata, 1400K init, 1308K bss, 187072K reserved, 0K cma-reserved)
> 
> According to above data, the number of present_pages has increased by
> 40(thus 160K), linux will terminate the resuming process. But since
> [0x0000000020200000-0x0000000077517fff] is a subset of
> [0x0000000020200000-0x000000007753ffff], we should let system
> resume.

Ok, complex, but will work. But what happens in the opposite case? On
the next boot, bios gets you 160K less....

Can you do echo powerdown > /sys/power/disk to work around this?

								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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