[ofa-general] Re: mthca use of dma_sync_single is bogus

Michael S. Tsirkin mst at dev.mellanox.co.il
Wed Jul 18 06:36:31 PDT 2007


> Quoting Roland Dreier <rdreier at cisco.com>:
> Subject: Re: [ofa-general] Re: mthca use of dma_sync_single is bogus
> 
>  > Hmm. This means there's no way to sync a range within
>  > mapping created with map_sg?
> 
> It doesn't seem that there is one right now at least.
> 
>  > > It actually doesn't look too bad to replace our use of pci_map_sg()
>  > > with dma_map_single(), at least at first glance.  I'll try to write a
>  > > patch later.
>  > 
>  > Well, the reason map_sg is there is presumably because on some
>  > architectures it's worth it to try and make the region contigious in DMA space.
>  > But I agree this seems the lesser evil at this point ...
> 
> Given that we're already trying to allocate big chunks of physically
> contiguous memory, I think that any virtual merging we get is likely
> to be of very small benefit.
> 
> It is kind of a shame to give this up though.

Did we reach any conclusion? Are you switching to map_single?

-- 
MST



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