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

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Date:	Tue, 27 Sep 2011 18:56:44 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	Yinghai Lu <yinghai.lu@...cle.com>, 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 Tuesday, September 27, 2011, Takashi Iwai wrote:
> 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 :)

I wonder.  Does hibernation work on the machine in question with
acpi_sleep=nonvs and if so, is the problem reproducible with this
setting?

Rafael
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