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

To:	Lukas Hejtmanek <xhejtman@xxxxxxxxxxx>
Subject:	[Xen-devel] Re: mthca use of dma_sync_single is bogus
From:	Roland Dreier <rdreier@xxxxxxxxx>
Date:	Tue, 10 Jul 2007 12:08:43 -0700
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Cc:	Keir Fraser <keir@xxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, "Michael S. Tsirkin" <mst@xxxxxxxxxxxxxxxxxx>, general@xxxxxxxxxxxxxxxxxxxxx
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In-reply-to:	<20070710190018.GK3885@xxxxxxxxxxx> (Lukas Hejtmanek's message of "Tue, 10 Jul 2007 21:00:19 +0200")
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 > I think he spoke about coherent, didn't he? On i386/x86_64, the consistent 
 > and
 > coherent are the same but on some architectures they are not and I think that
 > using consistent (in particular pci_alloc_consistent) is exactly what should
 > be used. Keir also recommended to use this one.

coherent and consistent are synonyms.  It's confusing because there is
pci_alloc_consistent(), which is in general just a wrapper for
dma_alloc_coherent().

 > And moreover, it avoids using swiotlb and bounce buffers, I think. Am I 
 > right,
 > Keir?

Yes, but I'm not really willing to make things worse for standard i386
just to make Xen work a little better.

 - R.

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