Re: [Qemu-devel] Re: [PATCH 2 of 5] add can_dma/post_dma for direct IO

Avi Kivity
2008-12-15T06:25:06Z

Anthony Liguori wrote:
>>
>> I Wouldn't be surprised if some machines had a large memory mapped IO
>> space. Most of it might not be actively used, but once you start
>> considering 64-bit machines on 32-bit hosts these allocations would
>> become problematic.
>>
>
> At some level, any DMA API would fall apart here. Certain IO
> operations simply cannot be split (such as network send). If you pass
> don't pass a flag to the map function that says you can handle partial
> results, you must cope with map() returning NULL (by dropping the
> packet).
>

... and then you must cope with it. In all non-network dma clients. Or
in the dma api.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.