Re: [Qemu-devel] [0/13] RFC: Guest visible IOMMU

[David Gibson]

On Thu, Mar 22, 2012 at 02:50:25PM +0100, Wei Wang wrote:
> On 03/22/2012 03:14 AM, David Gibson wrote:
> >Here's another version of my series implementing the nevessary
> >framework for emulation of guest-visible IOMMUs.  I've incorporated
> >the feedback from the last posting.  I'm fairly confident that
> >preliminary patches 1-3 are ready to go in, the rest might still need
> >more consideration.
> >
> >In particular, if anyone has thoughts on how to handle the case where
> >an IOMMU mapping is invalidated by the guest where a qemu-side device
> >currently has that piece of IOVA-space dma_memory_map()ed, I'd be
> >interested to hear it.
> >
> >
> >
> 
> Hi David,
> I am Xen developer. Currently I am working on a hardware based iommu
> emulation for amd iommu v2 systems (we need this to enable iommuv2
> drivers in guest OS and therefore to passthroug gpgpu to hvm guest).
> In this work, only a virtual iommu device has to be registered on
> qemu bus and dma translations are still performed by iommu hardware.
> So I wonder if it is possible that I could integrate my work with
> yours. I had a proof-of-concept patch for qemu:
> 
> http://lists.xen.org/archives/html/xen-devel/2011-12/msg01269.html
> 
> my last post was:
> http://lists.xen.org/archives/html/xen-devel/2012-03/msg00591.html

I'd be very glad to see AMD IOMMU support integrated with my
infrastructure.  Eduard - Gabriel's original patch series included an
AMD IOMMU emulation, but since I'm not really familiar with that
IOMMU, and don't have the hardware to test it, I didn't feel confident
to attempt porting it to my new infrastructure.

I notice that you seem to be aiming mostly at pass-through.
Pass-through has some complications of its own - this patch series was
aimed firstly at IOMMU emulation, although I'm also concerned with
pass-through (we're currently struggling with how best to handle
pass-through for pSeries machines).

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson