Date: Tue, 19 Apr 2016 20:49:48 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
        "qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>, peterx@redhat.com,
        Cornelia Huck <cornelia.huck@de.ibm.com>,
        Stefan Hajnoczi <stefanha@redhat.com>, Kevin Wolf <kwolf@redhat.com>,
        Amit Shah <amit.shah@redhat.com>, qemu-block@nongnu.org,
        Jason Wang <jasowang@redhat.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Wei Liu <wei.liu2@citrix.com>,
        Linux Virtualization <virtualization@lists.linux-foundation.org>,
        kvm list <kvm@vger.kernel.org>
Subject: Re: [PATCH RFC] fixup! virtio: convert to use DMA api
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On Tue, Apr 19, 2016 at 12:26:44PM -0400, David Woodhouse wrote:
> On Tue, 2016-04-19 at 19:20 +0300, Michael S. Tsirkin wrote:
> > 
> > > I thought that PLATFORM served that purpose.? Woudn't the host
> > > advertise PLATFORM support and, if the guest doesn't ack it, the host
> > > device would skip translation?? Or is that problematic for vfio?
> > 
> > Exactly that's problematic for security.
> > You can't allow guest driver to decide whether device skips security.
> 
> Right. Because fundamentally, this *isn't* a property of the endpoint
> device, and doesn't live in virtio itself.
> 
> It's a property of the platform IOMMU, and lives there.

It's a property of the hypervisor virtio implementation, and lives there.

-- 
MST