[lkml]   [2009]   [Jul]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: IOMMU and graphics cards
    On Mon, Jul 06, 2009 at 10:35:59PM +0100, Dave Airlie wrote:
    > 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*
    > > 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.

    Are you sure that using the dma-api has such an performance impact? I've
    heard from other people that switching to dma-api with amd iommu had no
    significant performance impact.

    > 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.

    You just need to switch to dma-api. You don't need an iommu to test.
    Most bugs in such code can also be found and eliminated using the
    dma-api debugging interface.


    | Advanced Micro Devices GmbH
    Operating | Karl-Hammerschmidt-Str. 34, 85609 Dornach bei München
    System |
    Research | Geschäftsführer: Thomas M. McCoy, Giuliano Meroni
    Center | Sitz: Dornach, Gemeinde Aschheim, Landkreis München
    | Registergericht München, HRB Nr. 43632

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2009-07-07 11:01    [W:0.026 / U:10.260 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site