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

drivers/gpu/drm/drm_gem.c

@@ -1161,7 +1161,7 @@ void drm_gem_print_info(struct drm_printer *p, unsigned int indent,
 		obj->funcs->print_info(p, indent, obj);
 }
 
-int drm_gem_pin(struct drm_gem_object *obj)
+int drm_gem_pin_locked(struct drm_gem_object *obj)
 {
 	if (obj->funcs->pin)
 		return obj->funcs->pin(obj);
@@ -1169,12 +1169,30 @@ int drm_gem_pin(struct drm_gem_object *obj)
 	return 0;
 }
 
-void drm_gem_unpin(struct drm_gem_object *obj)
+void drm_gem_unpin_locked(struct drm_gem_object *obj)
 {
 	if (obj->funcs->unpin)
 		obj->funcs->unpin(obj);
 }
 
+int drm_gem_pin(struct drm_gem_object *obj)
+{
+	int ret;
+
+	dma_resv_lock(obj->resv, NULL);
+	ret = drm_gem_pin_locked(obj);
+	dma_resv_unlock(obj->resv);
+
+	return ret;
+}
+
+void drm_gem_unpin(struct drm_gem_object *obj)
+{
+	dma_resv_lock(obj->resv, NULL);
+	drm_gem_unpin_locked(obj);
+	dma_resv_unlock(obj->resv);
+}
+
 int drm_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)
 {
 	int ret;

drivers/gpu/drm/drm_gem_vram_helper.c

@@ -774,11 +774,6 @@ EXPORT_SYMBOL(drm_gem_vram_simple_display_pipe_cleanup_fb);
 static int drm_gem_vram_object_pin(struct drm_gem_object *gem)
 {
 	struct drm_gem_vram_object *gbo = drm_gem_vram_of_gem(gem);
-	int ret;
-
-	ret = ttm_bo_reserve(&gbo->bo, true, false, NULL);
-	if (ret)
-		return ret;
 
 	/*
 	 * Fbdev console emulation is the use case of these PRIME
@@ -789,10 +784,7 @@ static int drm_gem_vram_object_pin(struct drm_gem_object *gem)
 	 * the buffer to be pinned to VRAM, implement a callback that
 	 * sets the flags accordingly.
 	 */
-	ret = drm_gem_vram_pin_locked(gbo, 0);
-	ttm_bo_unreserve(&gbo->bo);
-
-	return ret;
+	return drm_gem_vram_pin_locked(gbo, 0);
 }
 
 /**
@@ -803,13 +795,8 @@ static int drm_gem_vram_object_pin(struct drm_gem_object *gem)
 static void drm_gem_vram_object_unpin(struct drm_gem_object *gem)
 {
 	struct drm_gem_vram_object *gbo = drm_gem_vram_of_gem(gem);
-	int ret;
 
-	ret = ttm_bo_reserve(&gbo->bo, true, false, NULL);
-	if (ret)
-		return;
 	drm_gem_vram_unpin_locked(gbo);
-	ttm_bo_unreserve(&gbo->bo);
 }
 
 /**

drivers/gpu/drm/drm_internal.h

@@ -173,6 +173,8 @@ void drm_gem_release(struct drm_device *dev, struct drm_file *file_private);
 void drm_gem_print_info(struct drm_printer *p, unsigned int indent,
 			const struct drm_gem_object *obj);
 
+int drm_gem_pin_locked(struct drm_gem_object *obj);
+void drm_gem_unpin_locked(struct drm_gem_object *obj);
 int drm_gem_pin(struct drm_gem_object *obj);
 void drm_gem_unpin(struct drm_gem_object *obj);
 int drm_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map);

drivers/gpu/drm/loongson/lsdc_gem.c

@@ -19,33 +19,24 @@ static int lsdc_gem_prime_pin(struct drm_gem_object *obj)
 	struct lsdc_bo *lbo = gem_to_lsdc_bo(obj);
 	int ret;
 
-	ret = lsdc_bo_reserve(lbo);
-	if (unlikely(ret))
-		return ret;
+	dma_resv_assert_held(obj->resv);
 
 	ret = lsdc_bo_pin(lbo, LSDC_GEM_DOMAIN_GTT, NULL);
 	if (likely(ret == 0))
 		lbo->sharing_count++;
 
-	lsdc_bo_unreserve(lbo);
-
 	return ret;
 }
 
 static void lsdc_gem_prime_unpin(struct drm_gem_object *obj)
 {
 	struct lsdc_bo *lbo = gem_to_lsdc_bo(obj);
-	int ret;
 
-	ret = lsdc_bo_reserve(lbo);
-	if (unlikely(ret))
-		return;
+	dma_resv_assert_held(obj->resv);
 
 	lsdc_bo_unpin(lbo);
 	if (lbo->sharing_count)
 		lbo->sharing_count--;
-
-	lsdc_bo_unreserve(lbo);
 }
 
 static struct sg_table *lsdc_gem_prime_get_sg_table(struct drm_gem_object *obj)

drivers/gpu/drm/msm/msm_gem_prime.c

@@ -53,11 +53,9 @@ int msm_gem_prime_pin(struct drm_gem_object *obj)
 	if (obj->import_attach)
 		return 0;
 
-	msm_gem_lock(obj);
 	pages = msm_gem_pin_pages_locked(obj);
 	if (IS_ERR(pages))
 		ret = PTR_ERR(pages);
-	msm_gem_unlock(obj);
 
 	return ret;
 }
@@ -67,7 +65,5 @@ void msm_gem_prime_unpin(struct drm_gem_object *obj)
 	if (obj->import_attach)
 		return;
 
-	msm_gem_lock(obj);
 	msm_gem_unpin_pages_locked(obj);
-	msm_gem_unlock(obj);
 }

drivers/gpu/drm/nouveau/nouveau_prime.c

@@ -86,17 +86,12 @@ struct drm_gem_object *nouveau_gem_prime_import_sg_table(struct drm_device *dev,
 int nouveau_gem_prime_pin(struct drm_gem_object *obj)
 {
 	struct nouveau_bo *nvbo = nouveau_gem_object(obj);
-	struct ttm_buffer_object *bo = &nvbo->bo;
 	int ret;
 
-	ret = ttm_bo_reserve(bo, false, false, NULL);
-	if (ret)
-		return -EINVAL;
 	/* pin buffer into GTT */
 	ret = nouveau_bo_pin_locked(nvbo, NOUVEAU_GEM_DOMAIN_GART, false);
 	if (ret)
 		ret = -EINVAL;
-	ttm_bo_unreserve(bo);
 
 	return ret;
 }
@@ -104,14 +99,8 @@ int nouveau_gem_prime_pin(struct drm_gem_object *obj)
 void nouveau_gem_prime_unpin(struct drm_gem_object *obj)
 {
 	struct nouveau_bo *nvbo = nouveau_gem_object(obj);
-	struct ttm_buffer_object *bo = &nvbo->bo;
-	int ret;
 
-	ret = ttm_bo_reserve(bo, false, false, NULL);
-	if (ret)
-		return;
 	nouveau_bo_unpin_locked(nvbo);
-	ttm_bo_unreserve(bo);
 }
 
 struct dma_buf *nouveau_gem_prime_export(struct drm_gem_object *gobj,

drivers/gpu/drm/qxl/qxl_prime.c

@@ -31,27 +31,15 @@
 int qxl_gem_prime_pin(struct drm_gem_object *obj)
 {
 	struct qxl_bo *bo = gem_to_qxl_bo(obj);
-	int r;
 
-	r = qxl_bo_reserve(bo);
-	if (r)
-		return r;
-	r = qxl_bo_pin_locked(bo);
-	qxl_bo_unreserve(bo);
-
-	return r;
+	return qxl_bo_pin_locked(bo);
 }
 
 void qxl_gem_prime_unpin(struct drm_gem_object *obj)
 {
 	struct qxl_bo *bo = gem_to_qxl_bo(obj);
-	int r;
 
-	r = qxl_bo_reserve(bo);
-	if (r)
-		return;
 	qxl_bo_unpin_locked(bo);
-	qxl_bo_unreserve(bo);
 }
 
 struct sg_table *qxl_gem_prime_get_sg_table(struct drm_gem_object *obj)

drivers/gpu/drm/radeon/radeon_prime.c

@@ -73,32 +73,21 @@ int radeon_gem_prime_pin(struct drm_gem_object *obj)
 	struct radeon_bo *bo = gem_to_radeon_bo(obj);
 	int ret = 0;
 
-	ret = radeon_bo_reserve(bo, false);
-	if (unlikely(ret != 0))
-		return ret;
-
 	/* pin buffer into GTT */
 	ret = radeon_bo_pin(bo, RADEON_GEM_DOMAIN_GTT, NULL);
 	if (likely(ret == 0))
 		bo->prime_shared_count++;
 
-	radeon_bo_unreserve(bo);
 	return ret;
 }
 
 void radeon_gem_prime_unpin(struct drm_gem_object *obj)
 {
 	struct radeon_bo *bo = gem_to_radeon_bo(obj);
-	int ret = 0;
-
-	ret = radeon_bo_reserve(bo, false);
-	if (unlikely(ret != 0))
-		return;
 
 	radeon_bo_unpin(bo);
 	if (bo->prime_shared_count)
 		bo->prime_shared_count--;
-	radeon_bo_unreserve(bo);
 }
 
 

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)

include/drm/drm_gem_shmem_helper.h

@@ -175,15 +175,8 @@ static inline void drm_gem_shmem_object_print_info(struct drm_printer *p, unsign
 static inline int drm_gem_shmem_object_pin(struct drm_gem_object *obj)
 {
 	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
-	int ret;
 
-	ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
-	if (ret)
-		return ret;
-	ret = drm_gem_shmem_pin_locked(shmem);
-	dma_resv_unlock(shmem->base.resv);
-
-	return ret;
+	return drm_gem_shmem_pin_locked(shmem);
 }
 
 /**
@@ -197,9 +190,7 @@ static inline void drm_gem_shmem_object_unpin(struct drm_gem_object *obj)
 {
 	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
 
-	dma_resv_lock(shmem->base.resv, NULL);
 	drm_gem_shmem_unpin_locked(shmem);
-	dma_resv_unlock(shmem->base.resv);
 }
 
 /**