linux-kernel - Re: [PATCH]: x86_64, audio: Fix system panic when DMA

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Date:	Thu, 02 May 2013 10:29:33 +0200
From:	David Henningsson <david.henningsson@...onical.com>
To:	Mike Travis <travis@....com>
CC:	Stephen Warren <swarren@...dia.com>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>,
	Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
	Russ Anderson <rja@....com>
Subject: Re: [PATCH]: x86_64, audio: Fix system panic when DMA > 40 bits

On 05/02/2013 08:36 AM, Mike Travis wrote:
>
>
> On 5/1/2013 11:20 PM, David Henningsson wrote:
>> On 05/01/2013 09:04 PM, Mike Travis wrote:
>>> The audio driver mistakenly allows 64 bit addresses to be created for
>>> the audio driver on Nvidia GPUs.  Unfortunately, the hardware normally
>>> only supports up to 40 bits of DMA.  This can cause system panics as
>>> well as misdirected data when the address is > 40 bits as the upper
>>> part the address is truncated.
>>
>> Thanks for this patch. Stephen Warren, is this something you can
>> confirm/deny, and do you know what range of hardware this actually
>> applies to?
>
> The dma_mask can be read from the gpu device's pci entry.  I know it's
> a stretch to try to link to that but past history has shown that it
> ranges from 36 to 40 bits.

Ok, so the below patch is some kind of workaround, as we don't currently 
take the dma_mask into account correctly? Or put in another way, would 
it be possible/better to actually read the dma_mask and use that instead 
of just clamping at 32 bit?

>
>>
>>>
>>> Signed-off-by: Mike Travis <travis@....com>
>>> Reviewed-by: Mike Habeck <habeck@....com>
>>> ---
>>>    sound/pci/hda/hda_intel.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
>>> index bcd40ee..45eb165 100644
>>> --- a/sound/pci/hda/hda_intel.c
>>> +++ b/sound/pci/hda/hda_intel.c
>>> @@ -615,7 +615,7 @@ enum {
>>>    /* quirks for Nvidia */
>>>    #define AZX_DCAPS_PRESET_NVIDIA \
>>>        (AZX_DCAPS_NVIDIA_SNOOP | AZX_DCAPS_RIRB_DELAY |
>>> AZX_DCAPS_NO_MSI |\
>>> -     AZX_DCAPS_ALIGN_BUFSIZE)
>>> +     AZX_DCAPS_ALIGN_BUFSIZE | AZX_DCAPS_NO_64BIT)
>>>
>>>    #define AZX_DCAPS_PRESET_CTHDA \
>>>        (AZX_DCAPS_NO_MSI | AZX_DCAPS_POSFIX_LPIB |
>>> AZX_DCAPS_4K_BDLE_BOUNDARY)
>>>
>>
>>
>>
>



-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic
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