On Thu, Oct 24, 2019 at 02:18:59PM -0500, Rob Herring wrote:
Commit c40069cb7bd6 ("drm: add mmap() to drm_gem_object_funcs") introduced a GEM object mmap() hook which is expected to subtract the fake offset from vm_pgoff. However, for mmap() on dmabufs, there is not a fake offset.
To fix this, let's always call mmap() object callback with an offset of 0, and leave it up to drm_gem_mmap_obj() to remove the fake offset.
TTM still needs the fake offset, so we have to add it back until that's fixed.
Fixing ttm looks easy, there are not many calls to drm_vma_node_start() the ttm code. Can look into this when I'm back from kvm forum @ lyon.
int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo) { ttm_bo_get(bo);
- /*
* FIXME: &drm_gem_object_funcs.mmap is called with the fake offset* removed. Add it back here until the rest of TTM works without it.*/- vma->vm_pgoff += drm_vma_node_start(&bo->base.vma_node);
- ttm_bo_mmap_vma_setup(bo, vma); return 0;
}
Yes, that should keep ttm happy for now. Survived a quick smoke test with qemu and bochs.
Acked-by: Gerd Hoffmann kraxel@redhat.com
cheers, Gerd