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[Qemu-devel] Re: [RFC PATCH 0/5] QEMU VFIO device assignment


From: Avi Kivity
Subject: [Qemu-devel] Re: [RFC PATCH 0/5] QEMU VFIO device assignment
Date: Sun, 11 Jul 2010 21:43:37 +0300
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On 07/11/2010 09:37 PM, Alex Williamson wrote:
On Sun, 2010-07-11 at 21:17 +0300, Avi Kivity wrote:
On 07/11/2010 09:09 PM, Alex Williamson wrote:
The following series implements QEMU device assignment using the
proposed VFIO/UIOMMU kernel interfaces.  See the last patch for
further vfio description.  I've tested this on the v2 VFIO patch,
with a number of fixes hacked in along the way.  I'll update when
Tom releases a new version of VFIO.  Hopefully this will provide
some support for the usefulness of such an interfaces.  Thanks,


What's the plan for supporting this alongside the existing kvm device
assignment code?

vfio will only exist in very new kernels, so we have to support the old
code for a while to give people chance to adjust (say 12-18 months).
I was thinking that vfio device assignment might be the qemu acceptable
version of device assignment, and we can let kvm style device assignment
live out it's remaining time in the qemu-kvm tree, before it gets
deprecated.

Definitely, the effort to make qemu-kvm device assignment mergable probably isn't worth it.

Ideally we'd have compatible command line syntax with qemu choosing vfio
if available and falling back to kvm device assignment if not.
Ideally, yes, but I'm not sure how how feasible that is.  For the
command line root user, the syntax is nearly same (s/pci-assign/vfio/),
but once we start trying to do libvirt based assignment, passing vfiofd
&  uiommufd, it will need to know the difference anyway.  Thanks,

I see. Well, we can probably live with two separate invocations, users who assign devices should be savvy or use libvirt.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.




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