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Date: Tue, 27 Sep 2011 18:38:49 +0200
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From: Takashi Iwai <tiwai@suse.de>
To: Yinghai Lu <yinghai.lu@oracle.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>, linux-kernel@vger.kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>, oneukum@suse.de, x86@kernel.org,
        Linux PM mailing list <linux-pm@lists.linux-foundation.org>,
        Ingo Molnar <mingo@redhat.com>
Subject: Re: S4 resume broken since 2.6.39 (3.1, too)
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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@sisk.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