From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [RFC V2] virtio: Add platform specific DMA API translation for
	virito devices
Date: Fri, 15 Jun 2018 02:16:24 -0700
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To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: robh@kernel.org, cohuck@redhat.com, pawel.moll@arm.com, Tom Lendacky <thomas.lendacky@amd.com>, "Michael S. Tsirkin" <mst@redhat.com>, Ram Pai <linuxram@us.ibm.com>, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Christoph Hellwig <hch@infradead.org>, joe@perches.com, "Rustad,
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On Wed, Jun 13, 2018 at 11:11:01PM +1000, Benjamin Herrenschmidt wrote:
> Actually ... the stuff in lib/dma-direct.c seems to be just it, no ?
> 
> There's no cache flushing and there's no architecture hooks that I can
> see other than the AMD security stuff which is probably fine.
> 
> Or am I missing something ?

You are missing the __phys_to_dma arch hook that allows architectures
to adjust the dma address.  Various systems have offsets, or even
multiple banks with different offsets there.  Most of them don't
use the dma-direct code yet (working on it), but there are a few
examples in the tree already.