Re: Status of pci passthrough work?

[Amit Shah <amit.shah@redhat.com>]

* On Saturday 27 Sep 2008 13:27:46 Thomas Fjellstrom wrote:
> On Saturday 27 September 2008, Han, Weidong wrote:
> > Thomas Fjellstrom wrote:
> > > On Saturday 27 September 2008, Han, Weidong wrote:
> > >> Hi Thomas,
> > >>
> > >> the patches of passthrough/VT-d on kvm.git are already checked in.
> > >> With Amit's userspace patches, you can assign device to guest. You
> > >> can have a try.
> > >
> > > Does that mean I need VT-d support in hardware? All I have to test
> > > with right now is an AMD Phenom X4  with a 780g+sb700 system. Don't
> > > think it has an iommu, and I'd find it odd if the intel VT-d code
> > > "just worked" on amd's hardware.
> >
> > Yes, currently you need VT-d support in hardware to assign device.
>
> So I take it the PV-DMA (or pv-dma doesn't do what I think it does...) or
> the other 1:1 device pass through work isn't working right now?

pvdma does work, but the most recent patches aren't yet published (I should do 
that). It will work for simple devices.

1:1 will also work.

> It's something I'd really like to use, but I don't have access to a
> platform with a hardware iommu. Though I might be able to pick up a
> replacement board for my new server with the SB750 southbridge which
> supposedly has AMD's new iommu hardware in it, but I haven't seen any
> evidence that kvm or linux supports it.

Linux 2.6.27 onwards supports AMD IOMMU. kvm (and device assignment) support 
for AMD IOMMU doesn't exist yet, but work is planned to start soon.

> > >> Thomas Fjellstrom wrote:
> > >>> I'm very interested in being able to pass a few devices through to
> > >>> kvm guests. I'm wondering what exactly is working now, and how I
> > >>> can start testing it?
> > >>>
> > >>> the latest kvm release doesn't seem to include any support for it in
> > >>> userspace, so I can't test it with that...

The userspace patch is undergoing pre-merge revisions.

I'll send out an email once I get my git trees synced up to my working 
revisions.

In the meantime, you can use the patches from the list.