> What happens when another thread is using amdgpu_dmabuf_ops to call
> begin_cpu_access/end_cpu_access when you are fixing it up again?
Right, that is an issue.
> I would just completely drop the two callbacks, pinning is not necessary for
> CPU access and thinking more about it it actually has some unwanted side
> effects.
CPU access needs synchronization anyway, so the two callbacks cannot be dropped (other drivers implemented too), so I would like to keep it there for now.
Sam
> -----Original Message-----
> From: Koenig, Christian
> Sent: Wednesday, September 20, 2017 2:58 AM
> To: Li, Samuel <Samuel.Li at amd.com>; amd-gfx at lists.freedesktop.org
> Subject: Re: [PATCH v2 1/1] drm/amdgpu: Add gem_prime_mmap support
>
> > What do you mean "This isn't race free"?
>
> Take a look at the code again:
> > + dma_buf = drm_gem_prime_export(dev, gobj, flags);
> > + amdgpu_dmabuf_ops = *(dma_buf->ops);
> > + amdgpu_dmabuf_ops.begin_cpu_access =
> amdgpu_gem_begin_cpu_access;
> > + amdgpu_dmabuf_ops.end_cpu_access =
> amdgpu_gem_end_cpu_access;
> > + dma_buf->ops = &amdgpu_dmabuf_ops;
>
> What happens when another thread is using amdgpu_dmabuf_ops to call
> begin_cpu_access/end_cpu_access when you are fixing it up again?
>
> I would just completely drop the two callbacks, pinning is not necessary for
> CPU access and thinking more about it it actually has some unwanted side
> effects.
>
> Regards,
> Christian.
>
> Am 19.09.2017 um 23:22 schrieb Samuel Li:
> >>> + vma->vm_pgoff = amdgpu_bo_mmap_offset(bo) >> PAGE_SHIFT;
> >> Maybe better use "vma->vm_pgoff += amdgpu_bo_mmap_offset(bo) >>
> PAGE_SHIFT;", but I'm not sure.
> >> How other drivers handle this?
> > This is a good catch. Looks like pgoff is honored during prime mmap, not a
> fake offset here.
> >
> >>> + dma_buf->ops = &amdgpu_dmabuf_ops;
> >> This isn't race free and needs to be fixed.
> >> Better add callbacks to drm_prime.c similar to
> drm_gem_dmabuf_mmap().
> > What do you mean "This isn't race free"?
> >
> > Regards,
> > Sam
> >
> >
> >
> > On 2017-09-15 11:05 AM, Christian König wrote:
> >> Am 14.09.2017 um 00:39 schrieb Samuel Li:
> >>> v2: drop hdp invalidate/flush.
> >>>
> >>> Signed-off-by: Samuel Li <Samuel.Li at amd.com>
> >>> ---
> >>> drivers/gpu/drm/amd/amdgpu/amdgpu.h | 3 ++
> >>> drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 3 +-
> >>> drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c | 77
> ++++++++++++++++++++++++++++++-
> >>> 3 files changed, 81 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> >>> b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> >>> index d2aaad7..188b705 100644
> >>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> >>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> >>> @@ -395,11 +395,14 @@ amdgpu_gem_prime_import_sg_table(struct
> drm_device *dev,
> >>> struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
> >>> struct drm_gem_object *gobj,
> >>> int flags);
> >>> +struct drm_gem_object *amdgpu_gem_prime_import(struct
> drm_device *dev,
> >>> + struct dma_buf *dma_buf);
> >>> int amdgpu_gem_prime_pin(struct drm_gem_object *obj);
> >>> void amdgpu_gem_prime_unpin(struct drm_gem_object *obj);
> >>> struct reservation_object *amdgpu_gem_prime_res_obj(struct
> drm_gem_object *);
> >>> void *amdgpu_gem_prime_vmap(struct drm_gem_object *obj);
> >>> void amdgpu_gem_prime_vunmap(struct drm_gem_object *obj, void
> >>> *vaddr);
> >>> +int amdgpu_gem_prime_mmap(struct drm_gem_object *obj, struct
> >>> +vm_area_struct *vma);
> >>> int amdgpu_gem_debugfs_init(struct amdgpu_device *adev);
> >>> /* sub-allocation manager, it has to be protected by another lock.
> >>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> >>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> >>> index 2cdf844..9b63ac5 100644
> >>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> >>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> >>> @@ -835,7 +835,7 @@ static struct drm_driver kms_driver = {
> >>> .prime_handle_to_fd = drm_gem_prime_handle_to_fd,
> >>> .prime_fd_to_handle = drm_gem_prime_fd_to_handle,
> >>> .gem_prime_export = amdgpu_gem_prime_export,
> >>> - .gem_prime_import = drm_gem_prime_import,
> >>> + .gem_prime_import = amdgpu_gem_prime_import,
> >>> .gem_prime_pin = amdgpu_gem_prime_pin,
> >>> .gem_prime_unpin = amdgpu_gem_prime_unpin,
> >>> .gem_prime_res_obj = amdgpu_gem_prime_res_obj, @@ -843,6
> >>> +843,7 @@ static struct drm_driver kms_driver = {
> >>> .gem_prime_import_sg_table =
> amdgpu_gem_prime_import_sg_table,
> >>> .gem_prime_vmap = amdgpu_gem_prime_vmap,
> >>> .gem_prime_vunmap = amdgpu_gem_prime_vunmap,
> >>> + .gem_prime_mmap = amdgpu_gem_prime_mmap,
> >>> .name = DRIVER_NAME,
> >>> .desc = DRIVER_DESC,
> >>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> >>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> >>> index 5b3f928..13c977a 100644
> >>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> >>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
> >>> @@ -57,6 +57,40 @@ void amdgpu_gem_prime_vunmap(struct
> drm_gem_object *obj, void *vaddr)
> >>> ttm_bo_kunmap(&bo->dma_buf_vmap);
> >>> }
> >>> +int amdgpu_gem_prime_mmap(struct drm_gem_object *obj, struct
> >>> vm_area_struct *vma)
> >>> +{
> >>> + struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
> >>> + struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
> >>> + unsigned asize = amdgpu_bo_size(bo);
> >>> + int ret;
> >>> +
> >>> + if (!vma->vm_file)
> >>> + return -ENODEV;
> >>> +
> >>> + if (adev == NULL)
> >>> + return -ENODEV;
> >>> +
> >>> + /* Check for valid size. */
> >>> + if (asize < vma->vm_end - vma->vm_start)
> >>> + return -EINVAL;
> >>> +
> >>> + if (amdgpu_ttm_tt_get_usermm(bo->tbo.ttm) ||
> >>> + (bo->flags & AMDGPU_GEM_CREATE_NO_CPU_ACCESS)) {
> >>> + return -EPERM;
> >>> + }
> >>> + vma->vm_pgoff = amdgpu_bo_mmap_offset(bo) >> PAGE_SHIFT;
> >> Maybe better use "vma->vm_pgoff += amdgpu_bo_mmap_offset(bo) >>
> PAGE_SHIFT;", but I'm not sure.
> >>
> >> How other drivers handle this?
> >>
> >>> +
> >>> + /* prime mmap does not need to check access, so allow here */
> >>> + ret = drm_vma_node_allow(&obj->vma_node, vma->vm_file-
> >private_data);
> >>> + if (ret)
> >>> + return ret;
> >>> +
> >>> + ret = ttm_bo_mmap(vma->vm_file, vma, &adev->mman.bdev);
> >>> + drm_vma_node_revoke(&obj->vma_node,
> >>> + vma->vm_file->private_data);
> >>> +
> >>> + return ret;
> >>> +}
> >>> +
> >>> struct drm_gem_object *
> >>> amdgpu_gem_prime_import_sg_table(struct drm_device *dev,
> >>> struct dma_buf_attachment *attach, @@ -130,14
> >>> +164,55 @@ struct reservation_object
> *amdgpu_gem_prime_res_obj(struct drm_gem_object *obj)
> >>> return bo->tbo.resv;
> >>> }
> >>> +static int amdgpu_gem_begin_cpu_access(struct dma_buf *dma_buf,
> >>> enum dma_data_direction direction)
> >>> +{
> >>> + return amdgpu_gem_prime_pin(dma_buf->priv);
> >>> +}
> >>> +
> >>> +static int amdgpu_gem_end_cpu_access(struct dma_buf *dma_buf,
> enum
> >>> +dma_data_direction direction) {
> >>> + amdgpu_gem_prime_unpin(dma_buf->priv);
> >>> +
> >>> + return 0;
> >>> +}
> >>> +
> >>> +static struct dma_buf_ops amdgpu_dmabuf_ops;
> >>> +
> >>> struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
> >>> struct drm_gem_object *gobj,
> >>> int flags)
> >>> {
> >>> struct amdgpu_bo *bo = gem_to_amdgpu_bo(gobj);
> >>> + struct dma_buf *dma_buf;
> >>> if (amdgpu_ttm_tt_get_usermm(bo->tbo.ttm))
> >>> return ERR_PTR(-EPERM);
> >>> - return drm_gem_prime_export(dev, gobj, flags);
> >>> + dma_buf = drm_gem_prime_export(dev, gobj, flags);
> >>> + amdgpu_dmabuf_ops = *(dma_buf->ops);
> >>> + amdgpu_dmabuf_ops.begin_cpu_access =
> amdgpu_gem_begin_cpu_access;
> >>> + amdgpu_dmabuf_ops.end_cpu_access =
> amdgpu_gem_end_cpu_access;
> >>> + dma_buf->ops = &amdgpu_dmabuf_ops;
> >> This isn't race free and needs to be fixed.
> >>
> >> Better add callbacks to drm_prime.c similar to
> drm_gem_dmabuf_mmap().
> >>
> >> Alternative you could just completely drop
> amdgpu_gem_begin_cpu_access() and amdgpu_gem_end_cpu_access() as
> well.
> >>
> >> When the buffer is shared between device it is pinned anyway and when
> it isn't shared ttm_bo_mmap() is able to handle VRAM mappings as well.
> >>
> >> Regards,
> >> Christian.
> >>
> >>> +
> >>> + return dma_buf;
> >>> +}
> >>> +
> >>> +struct drm_gem_object *amdgpu_gem_prime_import(struct
> drm_device *dev,
> >>> + struct dma_buf *dma_buf) {
> >>> + struct drm_gem_object *obj;
> >>> +
> >>> + if (dma_buf->ops == &amdgpu_dmabuf_ops) {
> >>> + obj = dma_buf->priv;
> >>> + if (obj->dev == dev) {
> >>> + /*
> >>> + * Importing dmabuf exported from out own gem increases
> >>> + * refcount on gem itself instead of f_count of dmabuf.
> >>> + */
> >>> + drm_gem_object_get(obj);
> >>> + return obj;
> >>> + }
> >>> + }
> >>> +
> >>> + return drm_gem_prime_import(dev, dma_buf);
> >>> }
> >>
