linux-kernel - Re: S4 resume broken since 2.6.39 (3.1, too)

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Message-ID: <4E813464.80105@oracle.com>
Date:	Mon, 26 Sep 2011 19:26:44 -0700
From:	Yinghai Lu <yinghai.lu@...cle.com>
To:	Takashi Iwai <tiwai@...e.de>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org,
	"H. Peter Anvin" <hpa@...or.com>, oneukum@...e.de, x86@...nel.org,
	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: S4 resume broken since 2.6.39 (3.1, too)

On 09/22/2011 11:11 AM, Takashi Iwai wrote:

> At Thu, 22 Sep 2011 07:33:17 -0700,
> Yinghai Lu wrote:
>>
>> On Wed, Sep 21, 2011 at 11:48 AM, Rafael J. Wysocki <rjw@...k.pl> wrote:
>>> It looks like init_memory_mapping() is sometimes called with "end"
>>> beyond the last mapped PFN and it explodes when we try to write stuff to
>>> that address during image restoration.
>>>
>>> IOW, the Yinghai's assumption that init_memory_mapping() would always be
>>> called with a "good end" on x86_64 was overomptimistic.
>>
>> for 64bit x86, kernel_physical_mapping_init() will use
>> map_low_page()/call early_memmap() to access ram for page_table that is above
>> rather last mapped PFN.
>>
>> the point is:
>> on system with 64g, usable ram will be [0,2048m), [4g, 64g)
>> init_memory_mapping will be called two times for them.
>> before putting page_table high,
>> page table will be two parts: one is just below 512M, and one below 2048m.
>> after putting page_table high,
>> page table will be two parts: one is just below 2048M, and one below 64G.
> 
> So, how can this change break S4 resume?


not sure.

seems resume has it's own page table during transition...


> Any hint for further debugging?


you may try to insert dead loop in arch/x86/power/hibernate_asm_64.S::restore_image or core_restore_code

to see which part cause reset.

Yinghai


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