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Date:   Mon, 10 Sep 2018 10:53:16 +0200
From:   Gerd Hoffmann <kraxel@redhat.com>
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Jiandi An <jiandi@amd.com>, brijesh.singh@amd.com,
        srikar@linux.vnet.ibm.com, "Michael S. Tsirkin" <mst@redhat.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Will Deacon <will.deacon@arm.com>,
        virtualization@lists.linux-foundation.org, paulus@samba.org,
        elfring@users.sourceforge.net,
        Anshuman Khandual <khandual@linux.vnet.ibm.com>,
        robh@kernel.org, jean-philippe.brucker@arm.com, mpe@ellerman.id.au,
        thomas.lendacky@amd.com, marc.zyngier@arm.com, linuxram@us.ibm.com,
        david@gibson.dropbear.id.au, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, joe@perches.com, jiandi.an@amd.com,
        robin.murphy@arm.com, haren@linux.vnet.ibm.com
Subject: Re: [RFC 0/4] Virtio uses DMA API for all devices
Message-ID: <20180910085316.yzjbvoohqhdng2vb@sirius.home.kraxel.org>
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> > this to set the VIRTIO_F_IOMMU_PLATFORM flag. But for example
> > QEMU has the use of iommu_platform attribute disabled for virtio-gpu
> > device.  So would also like to move towards not having to specify
> > the VIRTIO_F_IOMMU_PLATFORM flag.
> 
> Specifying VIRTIO_F_IOMMU_PLATFORM is the right thing for your 
> platform given that you can't directly use physical addresses.
> Please fix qemu so that virtio-gpu works with VIRTIO_F_IOMMU_PLATFORM.

This needs both host and guest side changes btw.

Guest side patch is in drm-misc (a3b815f09bb8) and should land in the
next merge window.

Host side patches are here:
  https://git.kraxel.org/cgit/qemu/log/?h=sirius/virtio-gpu-iommu

Should also land in the next qemu version.

cheers,
  Gerd