Re: 2.6.23-rc8-mm1, -rc7-mm1 kill audio on HP nx6325

Re: 2.6.23-rc8-mm1, -rc7-mm1 kill audio on HP nx6325

[Andrew Morton]

On Tue, 25 Sep 2007 13:53:51 +0200 "Rafael J. Wysocki" <rjw@sisk.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 &&

Andi's taking a bit of time off, so we may need to park this until he
resurfaces.

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

[Jan Beulich]

>>> Andrew Morton <akpm@linux-foundation.org> 25.09.07 18:08 >>>
>On Tue, 25 Sep 2007 13:53:51 +0200 "Rafael J. Wysocki" <rjw@sisk.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

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

[Thomas Gleixner]

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