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Date:   Mon, 4 Jun 2018 19:34:19 +0300
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Anshuman Khandual <khandual@linux.vnet.ibm.com>,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
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        elfring@users.sourceforge.net, david@gibson.dropbear.id.au,
        jasowang@redhat.com, mpe@ellerman.id.au
Subject: Re: [RFC V2] virtio: Add platform specific DMA API translation for
 virito devices
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On Mon, Jun 04, 2018 at 11:14:36PM +1000, Benjamin Herrenschmidt wrote:
> On Mon, 2018-06-04 at 05:55 -0700, Christoph Hellwig wrote:
> > On Mon, Jun 04, 2018 at 03:43:09PM +0300, Michael S. Tsirkin wrote:
> > > Another is that given the basic functionality is in there, optimizations
> > > can possibly wait until per-device quirks in DMA API are supported.
> > 
> > We have had per-device dma_ops for quite a while.
> 
> I've asked Ansuman to start with a patch that converts virtio to use
> DMA ops always, along with an init quirk to hookup "direct" ops when
> the IOMMU flag isn't set.
> 
> This will at least remove that horrid duplication of code path we have
> in there.
> 
> Then we can just involve the arch in that init quirk so we can chose an
> alternate set of ops when running a secure VM.
> 
> This is completely orthogonal to whether an iommu exist qemu side or
> not, and should be entirely solved on the Linux side.
> 
> Cheers,
> Ben.

Sounds good to me.

-- 
MST