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.
>
> Fixes: c40069cb7bd6 ("drm: add mmap() to drm_gem_object_funcs")
> Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
> ---
> v2:
> - Move subtracting the fake offset out of mmap() obj callbacks.
>
> I've tested shmem, but not ttm. Hopefully, I understood what's needed
> for TTM.
>
> Rob
>
> drivers/gpu/drm/drm_gem.c | 3 +++
> drivers/gpu/drm/drm_gem_shmem_helper.c | 3 ---
> drivers/gpu/drm/ttm/ttm_bo_vm.c | 7 +++++++
> include/drm/drm_gem.h | 4 +++-
> 4 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 56f42e0f2584..2f2b889096b0 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -1106,6 +1106,9 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size,
> return -EINVAL;
>
> if (obj->funcs && obj->funcs->mmap) {
> + /* Remove the fake offset */
> + vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node);
> +
> ret = obj->funcs->mmap(obj, vma);
> if (ret)
> return ret;
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index a878c787b867..e8061c64c480 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -542,9 +542,6 @@ int drm_gem_shmem_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
> vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
> vma->vm_ops = &drm_gem_shmem_vm_ops;
>
> - /* Remove the fake offset */
> - vma->vm_pgoff -= drm_vma_node_start(&shmem->base.vma_node);
> -
> return 0;
> }
> EXPORT_SYMBOL_GPL(drm_gem_shmem_mmap);
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> index 1a9db691f954..08902c7290a5 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> @@ -482,6 +482,13 @@ EXPORT_SYMBOL(ttm_bo_mmap);
> 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;
> }
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index e71f75a2ab57..c56cbb3509e0 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -159,7 +159,9 @@ struct drm_gem_object_funcs {
> *
> * The callback is used by by both drm_gem_mmap_obj() and
> * drm_gem_prime_mmap(). When @mmap is present @vm_ops is not
> - * used, the @mmap callback must set vma->vm_ops instead.
> + * used, the @mmap callback must set vma->vm_ops instead. The @mmap
> + * callback is always called with a 0 offset. The caller will remove
> + * the fake offset as necessary.
> *
Maybe remove this empty comment line here while at it. With that
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
I think I'll follow up with a patch to annotate drm_gem_mmap_obj as
deprecated and that instead this here should be used.
-Daniel
> */
> int (*mmap)(struct drm_gem_object *obj, struct vm_area_struct *vma);
> --
> 2.20.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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