drm/gem: Acquire reservation lock in drm_gem_{pin/unpin}()

Acquire the buffer object's reservation lock in drm_gem_pin() and
remove locking the drivers' GEM callbacks where necessary. Same for
unpin().

DRM drivers and memory managers modified by this patch will now have
correct dma-buf locking semantics: the caller is responsible for
holding the reservation lock when calling the pin or unpin callback.

DRM drivers and memory managers that are not modified will now be
protected against concurent invocation of their pin and unpin callbacks.

PRIME does not implement struct dma_buf_ops.pin, which requires
the caller to hold the reservation lock. It does implement struct
dma_buf_ops.attach, which requires to callee to acquire the
reservation lock. The PRIME code uses drm_gem_pin(), so locks
are now taken as specified. Same for unpin and detach.

The patch harmonizes GEM pin and unpin to have non-interruptible
reservation locking across all drivers, as is already the case for
vmap and vunmap. This affects gem-shmem, gem-vram, loongson, qxl and
radeon.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Zack Rusin <zack.rusin@broadcom.com>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> # virtio-gpu
Link: https://patchwork.freedesktop.org/patch/msgid/20240227113853.8464-10-tzimmermann@suse.de

1 files changed, 6 insertions, 19 deletions

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_gem.c b/drivers/gpu/drm/vmwgfx/vmwgfx_gem.c
index 12787bb9c111..186150f41fbc 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_gem.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_gem.c
@@ -48,33 +48,20 @@ static void vmw_gem_object_close(struct drm_gem_object *obj,
 {
 }
 
-static int vmw_gem_pin_private(struct drm_gem_object *obj, bool do_pin)
+static int vmw_gem_object_pin(struct drm_gem_object *obj)
 {
-	struct ttm_buffer_object *bo = drm_gem_ttm_of_gem(obj);
 	struct vmw_bo *vbo = to_vmw_bo(obj);
-	int ret;
-
-	ret = ttm_bo_reserve(bo, false, false, NULL);
-	if (unlikely(ret != 0))
-		goto err;
-
-	vmw_bo_pin_reserved(vbo, do_pin);
-
-	ttm_bo_unreserve(bo);
-
-err:
-	return ret;
-}
 
+	vmw_bo_pin_reserved(vbo, true);
 
-static int vmw_gem_object_pin(struct drm_gem_object *obj)
-{
-	return vmw_gem_pin_private(obj, true);
+	return 0;
 }
 
 static void vmw_gem_object_unpin(struct drm_gem_object *obj)
 {
-	vmw_gem_pin_private(obj, false);
+	struct vmw_bo *vbo = to_vmw_bo(obj);
+
+	vmw_bo_pin_reserved(vbo, false);
 }
 
 static struct sg_table *vmw_gem_object_get_sg_table(struct drm_gem_object *obj)