[alsa-devel] [PATCH]: x86_64, audio: Fix system panic when DMA > 40 bits

[Mike Travis]

On 5/2/2013 11:20 AM, Stephen Warren wrote:
> On 05/02/2013 12:20 AM, 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?
> 
> It's certainly plausible that the GPU's internal physical addresses are
> less than a full 64-bits, and this probably affects PCI accesses too.
> 

I haven't noticed any other problems with MMIOH accesses.  The
problem of DMA32 addresses certainly affects us though audio is
not a high priority on UV(*) except in specific applications (like
Media Servers, etc.]  Accesses to the GPU and GPGPU are much more
common.

(* http://www.sgi.com/products/servers/uv/)