linux-kernel - Re: nouveau, linux3.7-rc3: BUG: unable to handle kernel paging request at fffffffffffffff8

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Date:	Mon, 5 Nov 2012 08:40:38 +0000
From:	Dave Airlie <airlied@...il.com>
To:	Antonio Ospite <ospite@...denti.unina.it>
Cc:	dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
	Ben Skeggs <bskeggs@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: nouveau, linux3.7-rc3: BUG: unable to handle kernel paging
 request at fffffffffffffff8

On Mon, Nov 5, 2012 at 8:29 AM, Antonio Ospite <ospite@...denti.unina.it> wrote:
> On Mon, 29 Oct 2012 23:16:24 +0100
> Antonio Ospite <ospite@...denti.unina.it> wrote:
>
>> Hi,
>>
>> I am experiencing a bug with nouveau with linux-3.7-rc3 (and since rc1),
>> my video adapter is the one integrated on the MSI M3N78-VM motherboard
>> (hence x86_64):
>>
> [...]
>> [ 1943.858601] BUG: unable to handle kernel paging request at fffffffffffffff8
>> [ 1943.858669] IP: [<ffffffffa031a67a>] nouveau_mm_head+0x30/0x127 [nouveau]
>> [ 1943.858779] PGD 160d067 PUD 160e067 PMD 0
>> [ 1943.858803] Oops: 0000 [#1] SMP
> [..]
>> [ 1943.860018] Call Trace:
>> [ 1943.860019]  [<ffffffff810fa13d>] ? kmem_cache_alloc_trace+0xbf/0xcf
>> [ 1943.860019]  [<ffffffff81060f13>] ? should_resched+0x5/0x23
>> [ 1943.860019]  [<ffffffffa032a10a>] ? nv50_fb_vram_new+0xc5/0x1f2 [nouveau]
>
> Ben, I cannot reproduce the crash with 3.7-rc4, I spotted commits
> a7dbf00 and 5cad16a which seem to be related to the problem I was
> having; would you mind elaborating a bit about what you think was
> causing the crash on my side? Maybe the chipset used on this motherboard
> doesn't support some feature? And how did you figured out from the logs?
>

5cad16acd25b16681a060d28d10eeacf98d07701 is the actual fix

The chipset hasn't got Z compression support, and the oops once decoded pointed
out the new code was trying to allocate Z tags from a NULL memory block. The old
code use to allocate an empty memory block instead of NULL, and it got
lost in the
rewrite, Ben just fixed it to allow empty memory blocks again.

Dave.
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