Re: [Intel-gfx] [Announcement] 2015-Q3 release of XenGT - a Mediated Graphics Passthrough Solution from Intel

From: Jike Song
Date: Thu Nov 19 2015 - 21:58:58 EST

On 11/19/2015 11:52 PM, Alex Williamson wrote:
On Thu, 2015-11-19 at 15:32 +0000, Stefano Stabellini wrote:
On Thu, 19 Nov 2015, Jike Song wrote:
Hi Alex, thanks for the discussion.

In addition to Kevin's replies, I have a high-level question: can VFIO
be used by QEMU for both KVM and Xen?

No. VFIO cannot be used with Xen today. When running on Xen, the IOMMU
is owned by Xen.

Right, but in this case we're talking about device MMUs, which are owned
by the device driver which I think is running in dom0, right? This
proposal doesn't require support of the system IOMMU, the dom0 driver
maps IOVA translations just as it would for itself. We're largely
proposing use of the VFIO API to provide a common interface to expose a
PCI(e) device to QEMU, but what happens in the vGPU vendor device and
IOMMU backends is specific to the device and perhaps even specific to
the hypervisor. Thanks,

Let me conclude this, and please correct me in case of any misread: the
vGPU interface between kernel and QEMU will be through VFIO, with a new
VFIO backend (instead of the existing type1), for both KVMGT and XenGT?


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