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Message-Id: <1190794950.23376.21.camel@chaos>
Date: Wed, 26 Sep 2007 10:22:30 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Jan Beulich <jbeulich@...ell.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
"Rafael J. Wysocki" <rjw@...k.pl>, Andi Kleen <ak@...e.de>,
Takashi Iwai <tiwai@...e.de>,
LKML <linux-kernel@...r.kernel.org>, discuss@...-64.org
Subject: Re: [discuss] 2.6.23-rc8-mm1, -rc7-mm1 kill audio on HP nx6325
On Wed, 2007-09-26 at 08:32 +0100, Jan Beulich wrote:
> >ioremap_nocache() does __ioremap(..., _PAGE_PCD);, then __ioremap() does
> >ioremap_page_range(..., _PAGE_PCD | other_stuff) That's one.
> >
> >__ioremap() then does ioremap_change_attr(..., _PAGE_PCD);. That's two.
> >
> >So I _think_ we're setting _PAGE_PCD twice on those pte's? Unclear. The
> >implementation is rather different from i386, too.
> >
> >I dunno why __change_page_attr() failed though. Perhaps this, in
> >change_page_attr_addr():
> >
> > if (!kernel_map || pte_present(pfn_pte(0, prot))) {
> >
> >should be &&
>
> Definitely not, and this code has been that way for a while.
>
> I rather suspect this change
>
> - if (!kpte) return 0;
> + if (!kpte)
> + return -EINVAL;
>
> to be the reason for the failure (and I had already sent a comment to this
> respect to Andi upon his review request).
This change exposes the problem. The question is why we do not have a
page table entry for the address, which was mapped right before that.
tglx
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