linux-kernel - Re: [discuss] 2.6.23-rc8-mm1, -rc7-mm1 kill audio on HP nx6325

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Date:	Wed, 26 Sep 2007 08:32:59 +0100
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	"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

>>> Andrew Morton <akpm@...ux-foundation.org> 25.09.07 18:08 >>>
>On Tue, 25 Sep 2007 13:53:51 +0200 "Rafael J. Wysocki" <rjw@...k.pl> wrote:
>
>> Hi,
>> 
>> This patch from Andi:
>> 
>> x86_64-mm-cpa-einval.patch
>> 
>> makes the hda_intel audio driver stop working on my HP nx6325.
>> 
>> The following line appears in dmesg (from 2.6.23-rc7-mm1:
>> 
>> ALSA /home/rafael/src/mm/linux-2.6.23-rc7-mm1/sound/pci/hda/hda_intel.c:1755: hd
>> a-intel: ioremap error
>> 
>> and the driver doesn't work afterwards.
>> 
>> Still, I'm not sure if the patch above is wrong or rather it exposes a problem
>> in the driver.
>> 
>
>Mysterious.
>
>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).

Jan

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