linux-kernel - Re: [PATCH RFC] fixup! virtio: convert to use DMA api

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Date:	Tue, 19 Apr 2016 12:26:44 -0400
From:	David Woodhouse <dwmw2@...radead.org>
To:	"Michael S. Tsirkin" <mst@...hat.com>,
	Andy Lutomirski <luto@...capital.net>
Cc:	"qemu-devel@...gnu.org Developers" <qemu-devel@...gnu.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Paolo Bonzini <pbonzini@...hat.com>, peterx@...hat.com,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Stefan Hajnoczi <stefanha@...hat.com>,
	Kevin Wolf <kwolf@...hat.com>,
	Amit Shah <amit.shah@...hat.com>, qemu-block@...gnu.org,
	Jason Wang <jasowang@...hat.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Wei Liu <wei.liu2@...rix.com>,
	Linux Virtualization <virtualization@...ts.linux-foundation.org>,
	kvm list <kvm@...r.kernel.org>
Subject: Re: [PATCH RFC] fixup! virtio: convert to use DMA api

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.

-- 
dwmw2


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