Re: Status of pci passthrough work?

[Thomas Fjellstrom <tfjellstrom@shaw.ca>]

On Sunday 28 September 2008, Amit Shah wrote:
> * 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.

Once the trees are updated?

> > 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.

What does the kernel supporting it help a person wanting to use it to pass 
through devices to guests if kvm doesn't support it? Also, what would the 
kernel use it for in that case?

> > > >> 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.

Its rather hard to find the patches from before I joined the list, most 
archives don't keep attachments.

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Thanks for the heads up, and all the work on this stuff :)

-- 
Thomas Fjellstrom
tfjellstrom@shaw.ca