linux-kernel - Re: -tip tree resume fail, bisect to 5bd5a45(x86: Add NX protection for kernel data)

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Date:	Fri, 26 Nov 2010 18:31:44 +0100
From:	mat <castet.matthieu@...e.fr>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Siarhei Liakh <sliakh.lkml@...il.com>,
	Xuxian Jiang <jiang@...ncsu.edu>, Ingo Molnar <mingo@...e.hu>,
	Arjan van de Ven <arjan@...radead.org>,
	lkml <linux-kernel@...r.kernel.org>, tglx <tglx@...utronix.de>
Subject: Re: -tip tree resume fail, bisect to 5bd5a45(x86: Add NX protection
 for kernel data)

Le Tue, 23 Nov 2010 23:55:27 +0100,
mat <castet.matthieu@...e.fr> a écrit :

> Le Mon, 22 Nov 2010 17:42:47 +0100,
> Andi Kleen <andi@...stfloor.org> a écrit :
> 
> > > That seems to be a S3 specific code path, that won't fix anything.
> > > Simply do:
> > > 
> > > echo 0 > /sys/devices/system/cpu/cpu1/online;
> > > echo 1 > /sys/devices/system/cpu/cpu1/online;
> > > 
> > > and your machine will explode..
> > 
> > The SMP startup trampoline is copied I believe
> > and only executed in real mode without page tables.
> > 
> > So it's perhaps not the trampoline, but the early startup 
> > code that ends up being broken.
> yes :
> acpi wakeup code and smp trampoline are copied in low memory (first
> 1MB).
> 
> So they can't end up int the kernel data mapping ?
> 
> So it should something else.
> 
> I will try to investigate on this.
> 
Unfortunately on my laptop supporting NX, suspend to ram seems broken
(even without this patch) and I got only one core, so I am unable to
test it.

Does cpu suspend/resume is broken ? Or it is only S3 ?

If yes, are there any interesting trace if we suspend only one core with
sysfs.

Thanks,

Matthieu
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