drm/ttm, drm/vmwgfx: move cpu_writers handling into vmwgfx

This feature is only used by vmwgfx and superfluous for everybody else.
Signed-off-by: Christian König <christian.koenig@amd.com>
Co-developed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Tested-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/333650/

drivers/gpu/drm/ttm/ttm_bo.c

@@ -153,7 +153,6 @@ static void ttm_bo_release_list(struct kref *list_kref)
 
 	BUG_ON(kref_read(&bo->list_kref));
 	BUG_ON(kref_read(&bo->kref));
-	BUG_ON(atomic_read(&bo->cpu_writers));
 	BUG_ON(bo->mem.mm_node != NULL);
 	BUG_ON(!list_empty(&bo->lru));
 	BUG_ON(!list_empty(&bo->ddestroy));
@@ -1315,7 +1314,6 @@ int ttm_bo_init_reserved(struct ttm_bo_device *bdev,
 
 	kref_init(&bo->kref);
 	kref_init(&bo->list_kref);
-	atomic_set(&bo->cpu_writers, 0);
 	INIT_LIST_HEAD(&bo->lru);
 	INIT_LIST_HEAD(&bo->ddestroy);
 	INIT_LIST_HEAD(&bo->swap);
@@ -1827,31 +1825,6 @@ int ttm_bo_wait(struct ttm_buffer_object *bo,
 }
 EXPORT_SYMBOL(ttm_bo_wait);
 
-int ttm_bo_synccpu_write_grab(struct ttm_buffer_object *bo, bool no_wait)
-{
-	int ret = 0;
-
-	/*
-	 * Using ttm_bo_reserve makes sure the lru lists are updated.
-	 */
-
-	ret = ttm_bo_reserve(bo, true, no_wait, NULL);
-	if (unlikely(ret != 0))
-		return ret;
-	ret = ttm_bo_wait(bo, true, no_wait);
-	if (likely(ret == 0))
-		atomic_inc(&bo->cpu_writers);
-	ttm_bo_unreserve(bo);
-	return ret;
-}
-EXPORT_SYMBOL(ttm_bo_synccpu_write_grab);
-
-void ttm_bo_synccpu_write_release(struct ttm_buffer_object *bo)
-{
-	atomic_dec(&bo->cpu_writers);
-}
-EXPORT_SYMBOL(ttm_bo_synccpu_write_release);
-
 /**
  * A buffer object shrink method that tries to swap out the first
  * buffer object on the bo_global::swap_lru list.

drivers/gpu/drm/ttm/ttm_bo_util.c

@@ -511,7 +511,6 @@ static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
 	mutex_init(&fbo->base.wu_mutex);
 	fbo->base.moving = NULL;
 	drm_vma_node_reset(&fbo->base.base.vma_node);
-	atomic_set(&fbo->base.cpu_writers, 0);
 
 	kref_init(&fbo->base.list_kref);
 	kref_init(&fbo->base.kref);

drivers/gpu/drm/ttm/ttm_execbuf_util.c

@@ -113,12 +113,7 @@ int ttm_eu_reserve_buffers(struct ww_acquire_ctx *ticket,
 		struct ttm_buffer_object *bo = entry->bo;
 
 		ret = __ttm_bo_reserve(bo, intr, (ticket == NULL), ticket);
-		if (!ret && unlikely(atomic_read(&bo->cpu_writers) > 0)) {
-			dma_resv_unlock(bo->base.resv);
-
-			ret = -EBUSY;
-
-		} else if (ret == -EALREADY && dups) {
+		if (ret == -EALREADY && dups) {
 			struct ttm_validate_buffer *safe = entry;
 			entry = list_prev_entry(entry, head);
 			list_del(&safe->head);

drivers/gpu/drm/vmwgfx/vmwgfx_bo.c

@@ -566,7 +566,7 @@ static void vmw_user_bo_ref_obj_release(struct ttm_base_object *base,
 
 	switch (ref_type) {
 	case TTM_REF_SYNCCPU_WRITE:
-		ttm_bo_synccpu_write_release(&user_bo->vbo.base);
+		atomic_dec(&user_bo->vbo.cpu_writers);
 		break;
 	default:
 		WARN_ONCE(true, "Undefined buffer object reference release.\n");
@@ -682,12 +682,12 @@ static int vmw_user_bo_synccpu_grab(struct vmw_user_buffer_object *user_bo,
 				    struct ttm_object_file *tfile,
 				    uint32_t flags)
 {
+	bool nonblock = !!(flags & drm_vmw_synccpu_dontblock);
 	struct ttm_buffer_object *bo = &user_bo->vbo.base;
 	bool existed;
 	int ret;
 
 	if (flags & drm_vmw_synccpu_allow_cs) {
-		bool nonblock = !!(flags & drm_vmw_synccpu_dontblock);
 		long lret;
 
 		lret = dma_resv_wait_timeout_rcu
@@ -700,15 +700,22 @@ static int vmw_user_bo_synccpu_grab(struct vmw_user_buffer_object *user_bo,
 		return 0;
 	}
 
-	ret = ttm_bo_synccpu_write_grab
-		(bo, !!(flags & drm_vmw_synccpu_dontblock));
+	ret = ttm_bo_reserve(bo, true, nonblock, NULL);
+	if (unlikely(ret != 0))
+		return ret;
+
+	ret = ttm_bo_wait(bo, true, nonblock);
+	if (likely(ret == 0))
+		atomic_inc(&user_bo->vbo.cpu_writers);
+
+	ttm_bo_unreserve(bo);
 	if (unlikely(ret != 0))
 		return ret;
 
 	ret = ttm_ref_object_add(tfile, &user_bo->prime.base,
 				 TTM_REF_SYNCCPU_WRITE, &existed, false);
 	if (ret != 0 || existed)
-		ttm_bo_synccpu_write_release(&user_bo->vbo.base);
+		atomic_dec(&user_bo->vbo.cpu_writers);
 
 	return ret;
 }

drivers/gpu/drm/vmwgfx/vmwgfx_drv.h

@@ -102,6 +102,8 @@ struct vmw_fpriv {
  * @base: The TTM buffer object
  * @res_list: List of resources using this buffer object as a backing MOB
  * @pin_count: pin depth
+ * @cpu_writers: Number of synccpu write grabs. Protected by reservation when
+ * increased. May be decreased without reservation.
  * @dx_query_ctx: DX context if this buffer object is used as a DX query MOB
  * @map: Kmap object for semi-persistent mappings
  * @res_prios: Eviction priority counts for attached resources
@@ -110,6 +112,7 @@ struct vmw_buffer_object {
 	struct ttm_buffer_object base;
 	struct list_head res_list;
 	s32 pin_count;
+	atomic_t cpu_writers;
 	/* Not ref-counted.  Protected by binding_mutex */
 	struct vmw_resource *dx_query_ctx;
 	/* Protected by reservation */

drivers/gpu/drm/vmwgfx/vmwgfx_validation.c

@@ -521,6 +521,9 @@ int vmw_validation_bo_validate_single(struct ttm_buffer_object *bo,
 	};
 	int ret;
 
+	if (atomic_read(&vbo->cpu_writers))
+		return -EBUSY;
+
 	if (vbo->pin_count > 0)
 		return 0;
 

include/drm/ttm/ttm_bo_api.h

@@ -147,7 +147,6 @@ struct ttm_tt;
  * holds a pointer to a persistent shmem object.
  * @ttm: TTM structure holding system pages.
  * @evicted: Whether the object was evicted without user-space knowing.
- * @cpu_writes: For synchronization. Number of cpu writers.
  * @lru: List head for the lru list.
  * @ddestroy: List head for the delayed destroy list.
  * @swap: List head for swap LRU list.
@@ -198,12 +197,6 @@ struct ttm_buffer_object {
 	struct ttm_tt *ttm;
 	bool evicted;
 
-	/**
-	 * Members protected by the bo::reserved lock only when written to.
-	 */
-
-	atomic_t cpu_writers;
-
 	/**
 	 * Members protected by the bdev::lru_lock.
 	 */
@@ -441,31 +434,6 @@ void ttm_bo_unlock_delayed_workqueue(struct ttm_bo_device *bdev, int resched);
 bool ttm_bo_eviction_valuable(struct ttm_buffer_object *bo,
 			      const struct ttm_place *place);
 
-/**
- * ttm_bo_synccpu_write_grab
- *
- * @bo: The buffer object:
- * @no_wait: Return immediately if buffer is busy.
- *
- * Synchronizes a buffer object for CPU RW access. This means
- * command submission that affects the buffer will return -EBUSY
- * until ttm_bo_synccpu_write_release is called.
- *
- * Returns
- * -EBUSY if the buffer is busy and no_wait is true.
- * -ERESTARTSYS if interrupted by a signal.
- */
-int ttm_bo_synccpu_write_grab(struct ttm_buffer_object *bo, bool no_wait);
-
-/**
- * ttm_bo_synccpu_write_release:
- *
- * @bo : The buffer object.
- *
- * Releases a synccpu lock.
- */
-void ttm_bo_synccpu_write_release(struct ttm_buffer_object *bo);
-
 /**
  * ttm_bo_acc_size
  *