linux-kernel - Re: [patch 0/4] x86: PAT followup - Incremental changes and bug fixes

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Date:	Thu, 17 Jan 2008 23:26:34 +0100
From:	"Andreas Herrmann3" <andreas.herrmann3@....com>
To:	"Ingo Molnar" <mingo@...e.hu>
cc:	"Venki Pallipadi" <venkatesh.pallipadi@...el.com>, ak@....de,
	ebiederm@...ssion.com, rdreier@...co.com,
	torvalds@...ux-foundation.org, gregkh@...e.de, airlied@...net.ie,
	davej@...hat.com, tglx@...utronix.de, hpa@...or.com,
	akpm@...ux-foundation.org, arjan@...radead.org,
	jesse.barnes@...el.com, davem@...emloft.net,
	linux-kernel@...r.kernel.org, suresh.b.siddha@...el.com
Subject: Re: [patch 0/4] x86: PAT followup - Incremental changes and bug
 fixes

On Thu, Jan 17, 2008 at 10:42:28PM +0100, Andreas Herrmann3 wrote:
> On Thu, Jan 17, 2008 at 10:13:08PM +0100, Ingo Molnar wrote:
> > 
> > * Andreas Herrmann3 <andreas.herrmann3@....com> wrote:
> > 
> > > Yes.
> > > 
> > > Meanwhile I have figured out that it is some ACPI stuff that maps the 
> > > page cached. I've changed the ioremap's in drivers/acpi/osl.c to 
> > > ioremap_nocache. See attached patch.
> > > 
> > > Now the machine boots without conflicts.
> > 
> > ah, nice!
> > 
> > but in general we must be robust enough in this case and just degrade 
> > any overlapping page to UC (and emit a warning perhaps) - instead of 
> > failing the ioremap and thus failing the driver (and the bootup).
> > 
> > Does my third patch (which falls back to UC in case of attribute 
> > conflicts, also attached below) instead of your ioremap_nocache() patch 
> > solve your bootup problem too?
> 
> I'll check this asap


So, now that I've avoided this tiny NULL-pointer-dereference, the system boots
fine as well with your (slightly modified) patch. See dmesg attached.


Andreas

View attachment "dmesg.log" of type "text/plain" (22892 bytes)