On Wed, Dec 09, 2020 at 03:25:25PM +0100, Thomas Zimmermann wrote:
> Implementations of the vmap/vunmap GEM callbacks may perform pinning
> of the BO and may acquire the associated reservation object's lock.
> Callers that only require a mapping of the contained memory can thus
> interfere with other tasks that require exact pinning, such as scanout.
> This is less of an issue with private SHMEM buffers, but may happen
> with imported ones.
>
> Therefore provide the new interfaces drm_gem_shmem_vmap_local() and
> drm_gem_shmem_vunmap_local(), which only perform the vmap/vunmap
> operations. Callers have to hold the reservation lock while the mapping
> persists.
>
> The affected callers are display updates in cirrus, gm12u320, mgag200
> and udl. All are being changed to the new interface.
>
> This patch also connects GEM SHMEM helpers to GEM object functions with
> equivalent functionality.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> ---
> drivers/gpu/drm/drm_gem_shmem_helper.c | 71 +++++++++++++++++++++++++-
> drivers/gpu/drm/mgag200/mgag200_mode.c | 16 ++++--
> drivers/gpu/drm/tiny/cirrus.c | 10 +++-
> drivers/gpu/drm/tiny/gm12u320.c | 14 +++--
> drivers/gpu/drm/udl/udl_modeset.c | 18 ++++---
I think that's a bit much driver conversion. I'd say in general split
these out from the patch that adds the new functionality. More
importantly, since vmap_local is optional, you can only start using it
once all drivers have it. Especially with udl this will break use-cases
otherwise, but also probably with gm12u320.
> include/drm/drm_gem_shmem_helper.h | 2 +
> 6 files changed, 115 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 9825c378dfa6..41663f48d46a 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -32,6 +32,8 @@ static const struct drm_gem_object_funcs drm_gem_shmem_funcs = {
> .get_sg_table = drm_gem_shmem_get_sg_table,
> .vmap = drm_gem_shmem_vmap,
> .vunmap = drm_gem_shmem_vunmap,
> + .vmap_local = drm_gem_shmem_vmap_local,
> + .vunmap_local = drm_gem_shmem_vunmap_local,
> .mmap = drm_gem_shmem_mmap,
> };
>
> @@ -313,7 +315,7 @@ static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct
> return ret;
> }
>
> -/*
> +/**
> * drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
> * @shmem: shmem GEM object
> * @map: Returns the kernel virtual address of the SHMEM GEM object's backing
> @@ -346,6 +348,44 @@ int drm_gem_shmem_vmap(struct drm_gem_object *obj, struct dma_buf_map *map)
> }
> EXPORT_SYMBOL(drm_gem_shmem_vmap);
>
> +/**
> + * drm_gem_shmem_vmap_local - Create a virtual mapping for a shmem GEM object
> + * @shmem: shmem GEM object
> + * @map: Returns the kernel virtual address of the SHMEM GEM object's backing
> + * store.
> + *
> + * This function makes sure that a contiguous kernel virtual address mapping
> + * exists for the buffer backing the shmem GEM object.
> + *
> + * The function is called with the BO's reservation object locked. Callers must
> + * hold the lock until after unmapping the buffer.
> + *
> + * This function can be used to implement &drm_gem_object_funcs.vmap_local. But
> + * it can also be called by drivers directly, in which case it will hide the
> + * differences between dma-buf imported and natively allocated objects.
> + *
> + * Acquired mappings should be cleaned up by calling drm_gem_shmem_vunmap_local().
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_shmem_vmap_local(struct drm_gem_object *obj, struct dma_buf_map *map)
> +{
> + struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> + int ret;
> +
> + dma_resv_assert_held(obj->resv);
> +
> + ret = mutex_lock_interruptible(&shmem->vmap_lock);
This bites. You need to check for shmem->import_attach and call
dma_buf_vmap_local directly here before you take any shmem helper locks.
Real fix would be to replace both vmap_lock and pages_lock with dma_resv
lock, but that's more work. Same for vunmap_local
With that fixed on the helper part of this patch:
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> + if (ret)
> + return ret;
> + ret = drm_gem_shmem_vmap_locked(shmem, map);
> + mutex_unlock(&shmem->vmap_lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL(drm_gem_shmem_vmap_local);
> +
> static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
> struct dma_buf_map *map)
> {
> @@ -366,7 +406,7 @@ static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
> drm_gem_shmem_put_pages(shmem);
> }
>
> -/*
> +/**
> * drm_gem_shmem_vunmap - Unmap a virtual mapping fo a shmem GEM object
> * @shmem: shmem GEM object
> * @map: Kernel virtual address where the SHMEM GEM object was mapped
> @@ -389,6 +429,33 @@ void drm_gem_shmem_vunmap(struct drm_gem_object *obj, struct dma_buf_map *map)
> }
> EXPORT_SYMBOL(drm_gem_shmem_vunmap);
>
> +/**
> + * drm_gem_shmem_vunmap_local - Unmap a virtual mapping fo a shmem GEM object
> + * @shmem: shmem GEM object
> + * @map: Kernel virtual address where the SHMEM GEM object was mapped
> + *
> + * This function cleans up a kernel virtual address mapping acquired by
> + * drm_gem_shmem_vmap_local(). The mapping is only removed when the use count
> + * drops to zero.
> + *
> + * The function is called with the BO's reservation object locked.
> + *
> + * This function can be used to implement &drm_gem_object_funcs.vmap_local.
> + * But it can also be called by drivers directly, in which case it will hide
> + * the differences between dma-buf imported and natively allocated objects.
> + */
> +void drm_gem_shmem_vunmap_local(struct drm_gem_object *obj, struct dma_buf_map *map)
> +{
> + struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> +
> + dma_resv_assert_held(obj->resv);
> +
> + mutex_lock(&shmem->vmap_lock);
> + drm_gem_shmem_vunmap_locked(shmem, map);
> + mutex_unlock(&shmem->vmap_lock);
> +}
> +EXPORT_SYMBOL(drm_gem_shmem_vunmap_local);
> +
> struct drm_gem_shmem_object *
> drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
> struct drm_device *dev, size_t size,
> diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
> index 1dfc42170059..a33e28d4c5e9 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_mode.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
> @@ -1552,22 +1552,32 @@ mgag200_handle_damage(struct mga_device *mdev, struct drm_framebuffer *fb,
> struct drm_rect *clip)
> {
> struct drm_device *dev = &mdev->base;
> + struct drm_gem_object *obj = fb->obj[0];
> struct dma_buf_map map;
> void *vmap;
> int ret;
>
> - ret = drm_gem_shmem_vmap(fb->obj[0], &map);
> + ret = dma_resv_lock(obj->resv, NULL);
> if (drm_WARN_ON(dev, ret))
> - return; /* BUG: SHMEM BO should always be vmapped */
> + return;
> + ret = drm_gem_shmem_vmap_local(obj, &map);
> + if (drm_WARN_ON(dev, ret))
> + goto err_dma_resv_unlock; /* BUG: SHMEM BO should always be vmapped */
> vmap = map.vaddr; /* TODO: Use mapping abstraction properly */
>
> drm_fb_memcpy_dstclip(mdev->vram, vmap, fb, clip);
>
> - drm_gem_shmem_vunmap(fb->obj[0], &map);
> + drm_gem_shmem_vunmap_local(obj, &map);
> + dma_resv_unlock(obj->resv);
>
> /* Always scanout image at VRAM offset 0 */
> mgag200_set_startadd(mdev, (u32)0);
> mgag200_set_offset(mdev, fb);
> +
> + return;
> +
> +err_dma_resv_unlock:
> + dma_resv_unlock(obj->resv);
> }
>
> static void
> diff --git a/drivers/gpu/drm/tiny/cirrus.c b/drivers/gpu/drm/tiny/cirrus.c
> index 561c49d8657a..58c694964148 100644
> --- a/drivers/gpu/drm/tiny/cirrus.c
> +++ b/drivers/gpu/drm/tiny/cirrus.c
> @@ -315,6 +315,7 @@ static int cirrus_fb_blit_rect(struct drm_framebuffer *fb,
> struct drm_rect *rect)
> {
> struct cirrus_device *cirrus = to_cirrus(fb->dev);
> + struct drm_gem_object *obj = fb->obj[0];
> struct dma_buf_map map;
> void *vmap;
> int idx, ret;
> @@ -323,9 +324,12 @@ static int cirrus_fb_blit_rect(struct drm_framebuffer *fb,
> if (!drm_dev_enter(&cirrus->dev, &idx))
> goto out;
>
> - ret = drm_gem_shmem_vmap(fb->obj[0], &map);
> + ret = dma_resv_lock(obj->resv, NULL);
> if (ret)
> goto out_dev_exit;
> + ret = drm_gem_shmem_vmap_local(fb->obj[0], &map);
> + if (ret)
> + goto out_dma_resv_unlock;
> vmap = map.vaddr; /* TODO: Use mapping abstraction properly */
>
> if (cirrus->cpp == fb->format->cpp[0])
> @@ -345,9 +349,11 @@ static int cirrus_fb_blit_rect(struct drm_framebuffer *fb,
> else
> WARN_ON_ONCE("cpp mismatch");
>
> - drm_gem_shmem_vunmap(fb->obj[0], &map);
> ret = 0;
>
> + drm_gem_shmem_vunmap_local(obj, &map);
> +out_dma_resv_unlock:
> + dma_resv_unlock(obj->resv);
> out_dev_exit:
> drm_dev_exit(idx);
> out:
> diff --git a/drivers/gpu/drm/tiny/gm12u320.c b/drivers/gpu/drm/tiny/gm12u320.c
> index 33f65f4626e5..b0c6e350f2b3 100644
> --- a/drivers/gpu/drm/tiny/gm12u320.c
> +++ b/drivers/gpu/drm/tiny/gm12u320.c
> @@ -265,11 +265,16 @@ static void gm12u320_copy_fb_to_blocks(struct gm12u320_device *gm12u320)
> y1 = gm12u320->fb_update.rect.y1;
> y2 = gm12u320->fb_update.rect.y2;
>
> - ret = drm_gem_shmem_vmap(fb->obj[0], &map);
> + ret = dma_resv_lock(fb->obj[0]->resv, NULL);
> if (ret) {
> - GM12U320_ERR("failed to vmap fb: %d\n", ret);
> + GM12U320_ERR("failed to reserve fb: %d\n", ret);
> goto put_fb;
> }
> + ret = drm_gem_shmem_vmap_local(fb->obj[0], &map);
> + if (ret) {
> + GM12U320_ERR("failed to vmap fb: %d\n", ret);
> + goto unlock_resv;
> + }
> vaddr = map.vaddr; /* TODO: Use mapping abstraction properly */
>
> if (fb->obj[0]->import_attach) {
> @@ -321,8 +326,11 @@ static void gm12u320_copy_fb_to_blocks(struct gm12u320_device *gm12u320)
> if (ret)
> GM12U320_ERR("dma_buf_end_cpu_access err: %d\n", ret);
> }
> +
> +unlock_resv:
> + dma_resv_unlock(fb->obj[0]->resv);
> vunmap:
> - drm_gem_shmem_vunmap(fb->obj[0], &map);
> + drm_gem_shmem_vunmap_local(fb->obj[0], &map);
> put_fb:
> drm_framebuffer_put(fb);
> gm12u320->fb_update.fb = NULL;
> diff --git a/drivers/gpu/drm/udl/udl_modeset.c b/drivers/gpu/drm/udl/udl_modeset.c
> index 9d34ec9d03f6..46b55b4d03c2 100644
> --- a/drivers/gpu/drm/udl/udl_modeset.c
> +++ b/drivers/gpu/drm/udl/udl_modeset.c
> @@ -290,14 +290,18 @@ static int udl_handle_damage(struct drm_framebuffer *fb, int x, int y,
> else if ((clip.x2 > fb->width) || (clip.y2 > fb->height))
> return -EINVAL;
>
> + ret = dma_resv_lock(fb->obj[0]->resv, NULL);
> + if (ret)
> + return ret;
> +
> if (import_attach) {
> ret = dma_buf_begin_cpu_access(import_attach->dmabuf,
> DMA_FROM_DEVICE);
> if (ret)
> - return ret;
> + goto out_dma_resv_unlock;
> }
>
> - ret = drm_gem_shmem_vmap(fb->obj[0], &map);
> + ret = drm_gem_shmem_vmap_local(fb->obj[0], &map);
> if (ret) {
> DRM_ERROR("failed to vmap fb\n");
> goto out_dma_buf_end_cpu_access;
> @@ -307,7 +311,7 @@ static int udl_handle_damage(struct drm_framebuffer *fb, int x, int y,
> urb = udl_get_urb(dev);
> if (!urb) {
> ret = -ENOMEM;
> - goto out_drm_gem_shmem_vunmap;
> + goto out_drm_gem_shmem_vunmap_local;
> }
> cmd = urb->transfer_buffer;
>
> @@ -320,7 +324,7 @@ static int udl_handle_damage(struct drm_framebuffer *fb, int x, int y,
> &cmd, byte_offset, dev_byte_offset,
> byte_width);
> if (ret)
> - goto out_drm_gem_shmem_vunmap;
> + goto out_drm_gem_shmem_vunmap_local;
> }
>
> if (cmd > (char *)urb->transfer_buffer) {
> @@ -336,8 +340,8 @@ static int udl_handle_damage(struct drm_framebuffer *fb, int x, int y,
>
> ret = 0;
>
> -out_drm_gem_shmem_vunmap:
> - drm_gem_shmem_vunmap(fb->obj[0], &map);
> +out_drm_gem_shmem_vunmap_local:
> + drm_gem_shmem_vunmap_local(fb->obj[0], &map);
> out_dma_buf_end_cpu_access:
> if (import_attach) {
> tmp_ret = dma_buf_end_cpu_access(import_attach->dmabuf,
> @@ -345,6 +349,8 @@ static int udl_handle_damage(struct drm_framebuffer *fb, int x, int y,
> if (tmp_ret && !ret)
> ret = tmp_ret; /* only update ret if not set yet */
> }
> +out_dma_resv_unlock:
> + dma_resv_unlock(fb->obj[0]->resv);
>
> return ret;
> }
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index 434328d8a0d9..3f59bdf749aa 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -114,7 +114,9 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem);
> int drm_gem_shmem_pin(struct drm_gem_object *obj);
> void drm_gem_shmem_unpin(struct drm_gem_object *obj);
> int drm_gem_shmem_vmap(struct drm_gem_object *obj, struct dma_buf_map *map);
> +int drm_gem_shmem_vmap_local(struct drm_gem_object *obj, struct dma_buf_map *map);
> void drm_gem_shmem_vunmap(struct drm_gem_object *obj, struct dma_buf_map *map);
> +void drm_gem_shmem_vunmap_local(struct drm_gem_object *obj, struct dma_buf_map *map);
>
> int drm_gem_shmem_madvise(struct drm_gem_object *obj, int madv);
>
> --
> 2.29.2
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
