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    SubjectRe: [PATCH] Export shmem_file_setup and shmem_getpage for DRM-GEM
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    On Thursday, August 21, 2008 6:42 am Jerome Glisse wrote:
    > On Tue, 19 Aug 2008 11:50:11 -0700
    >
    > Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
    > > As for in-kernel stuff, as long as we keep the GEM shmem hooks separate
    > > from the actual bookkeeping (like we do now with i915_gem_create_ioctl()
    > > vs drm_gem_object_alloc() for example) we should be able to do the
    > > in-kernel stuff w/o jumping through too many VFS/VM hoops. That would
    > > also assume we don't care about swapping in the in-kernel case, which we
    > > don't; we want to pin the kernel allocated frame buffer and other memory
    > > anyway, so using the internal functions should be fine.
    >
    > What about suspend to disk ? How do we save such buffers ?

    We'll have to deal with it like other kernel memory, or in the case of cards
    with VRAM maybe have a special hook that copies out the front buffer.
    Depends on how Dave implemented the GEM stuff on a device with VRAM (I
    haven't looked yet).

    > Btw i think that GTT looks a lot like IOMMU, i don't know the IOMMU kernel
    > side API that much, but from memory i think that you have call to ask IOMMU
    > mapping why not do somethings like that for GTT ?
    >
    > You get normal mapping of object diret but userspace can ask some kind of
    > GTT mapping on a given object. Anyway new flag on fd sounds good enough
    > too.

    At a high level that's pretty much what we're doing. We already have to map
    things through the GTT in the kernel for pwrite/pread etc., so that code is
    done. It's just exposing it to userspace that's a bit of a pain, since we
    have an all-ioctl interface...

    --
    Jesse Barnes, Intel Open Source Technology Center


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