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

[Avi Kivity]

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.