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

Alex Williamson
2010-07-11T18:37:20Z

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.

> 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,

Alex