[Xen-devel] Re: mthca use of dma_sync_single is bogus

[Lukas Hejtmanek <xhejtman@xxxxxxxxxxx>]

On Tue, Jul 10, 2007 at 12:24:02PM -0700, Roland Dreier wrote:
> Sorry, I was a little confusing.  The implementations may be different
> but in general there is no real difference between consistent and
> coherent memory.  Using either pci_alloc_consistent() or
> dma_alloc_coherent() will exhaust the same small pool of address space
> on powerpc 4xx for example.

I thought that consistent only refers to physically contiguous area whereas
coherent refers to memory where no barrier need to be used. But I may be
wrong.

Anyway, with my patch, I can turn off swiotlb and I'm still able to load
ib_mthca cleanly in DomU. On the other hand, Xen bug me about DMA bug in
ib_ipoib, there may be another problem with dma_sync_single().

> Seems pretty ugly, especially given that Xen is not upstream.  I think
> the Xen tree should just carry such patches, at least until Xen is
> merged.  Even then I'm quite dubious about having two code paths for this.

OK, I will keep it for my own.

-- 
Lukáš Hejtmánek

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