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Date: Thu, 22 Sep 2011 20:11:56 +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 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?
Any hint for further debugging?


thanks,

Takashi