Re: IOMMU and graphics cards

Dave Airlie
2009-07-06T21:36:12Z

On Mon, 6 Jul 2009, David Woodhouse wrote:

> On Mon, 2009-07-06 at 15:11 +0200, Joerg Roedel wrote:
> > Ok, cool, that sounds good. Which in-kernel DRM drivers break with IOMMU
> > for you? I'll may probably add a similar temporary workaround for AMD
> > IOMMU too...
>
> The Intel one definitely broke -- I don't know about the others. There
> are some old patches at http://people.freedesktop.org/~zhen/agp-mm-*
> which make it look like _all_ AGP drivers are broken.
>
> I wouldn't bother adding the workaround -- as I said, I'm planning to
> rip it out of 2.6.32 (and in linux-next as soon as it's reasonable to do
> so). Let's just let them fix it.

cc'ing Eric,

My memory of this is graphics becomes totally useless and can be 10x-50x
slower. I think ripping this out without the person doing the ripping
taking responsiblity for doing speed regression testing is totally insane.

I personally have no IOMMU hw from Intel or AMD and nobody has seen it fit
to supply me with any at any point in time, I'm not on the correct gravy
train. So I suspect the people with the hw will have to do the work and
the regression testing.

Dave.