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

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Date:	Tue, 27 Sep 2011 18:38:49 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Yinghai Lu <yinghai.lu@...cle.com>
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)

At Mon, 26 Sep 2011 19:26:44 -0700,
Yinghai Lu wrote:
> 
> 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.

That's the answer I was afraid of :)


Takashi
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