linux-kernel - Re: [Fastboot] [RFC] [PATCH 10/16] x86

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Date:	Wed, 15 Nov 2006 19:28:36 -0500
From:	Vivek Goyal <vgoyal@...ibm.com>
To:	linux kernel mailing list <linux-kernel@...r.kernel.org>
Cc:	akpm@...l.org, rjw@...k.pl, pavel@...e.cz, ebiederm@...ssion.com,
	hpa@...or.com, Reloc Kernel List <fastboot@...ts.osdl.org>,
	magnus.damm@...il.com, ak@...e.de, Don Zickus <dzickus@...hat.com>,
	Linda Wang <lwang@...hat.com>
Subject: Re: [Fastboot] [RFC] [PATCH 10/16] x86_64: 64bit PIC ACPI wakeup

On Wed, Nov 15, 2006 at 04:24:11PM -0500, Vivek Goyal wrote:
> On Mon, Nov 13, 2006 at 11:43:14AM -0500, Vivek Goyal wrote:
> > 
> > 
> > - Killed lots of dead code
> > - Improve the cpu sanity checks to verify long mode
> >   is enabled when we wake up.
> > - Removed the need for modifying any existing kernel page table.
> > - Moved wakeup_level4_pgt into the wakeup routine so we can
> >   run the kernel above 4G.
> > - Increased the size of the wakeup routine to 8K.
> > - Renamed the variables to use the 64bit register names.
> > - Lots of misc cleanups to match trampoline.S
> > 
> > I don't have a configuration I can test this but it compiles cleanly
> > and it should work, the code is very similar to the SMP trampoline,
> > which I have tested.  At least now the comments about still running in
> > low memory are actually correct.
> > 
> > Vivek has tested this patch for suspend to memory and it works fine.
> > 
> 
> More update. Got hold of another machine and suspend/resume seems to be
> facing problems.
> 
> With 2.6.19-rc5-git2
> --------------------
> - echo 3 > /proc/acpi/sleep (Suspend to memory takes place)
> - Press power button (System tries to come back but fails in MPT adapter
> 			initialization)
> 
> With 2.6.19-rc5-git2 + Reloc patches
> ------------------------------------
> - echo 3 > /proc/acpi/sleep (Suspend to memory takes place)
> - Press power button (Fan powers on but nothing additional is displayed on
> 			serial console.)
> 
> Will do a bisect and try to isolate the problem.
> 

Ok. In the new code NX bit protection feature is not being enabled and that
seems to be causing the problem. I checked and enabled the NX bit feature
in EFER in wakeup.S and it starts working.

I think my new machine supports NX bit protection feature and if while
resuming if I don't enable that feature back probably it must have caused
a GPF while loading the page tables which have got NX bit set. (A guess).

I know that previous machine I was testing on does not support NX bit
feature and that could be the reason that previous machine did not run into
the problems.

Thanks
Vivek
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