drm/ttm: stop always moving BOs on the LRU on page fault

Move the BO on the LRU only when it is actually moved by a DMA
operation.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Tested-And-Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/ttm/ttm_bo_vm.c

@@ -71,7 +71,7 @@ static vm_fault_t ttm_bo_vm_fault_idle(struct ttm_buffer_object *bo,
 		ttm_bo_get(bo);
 		up_read(&vmf->vma->vm_mm->mmap_sem);
 		(void) dma_fence_wait(bo->moving, true);
-		ttm_bo_unreserve(bo);
+		reservation_object_unlock(bo->resv);
 		ttm_bo_put(bo);
 		goto out_unlock;
 	}
@@ -131,11 +131,7 @@ static vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
 	 * for reserve, and if it fails, retry the fault after waiting
 	 * for the buffer to become unreserved.
 	 */
-	err = ttm_bo_reserve(bo, true, true, NULL);
-	if (unlikely(err != 0)) {
-		if (err != -EBUSY)
-			return VM_FAULT_NOPAGE;
-
+	if (unlikely(!reservation_object_trylock(bo->resv))) {
 		if (vmf->flags & FAULT_FLAG_ALLOW_RETRY) {
 			if (!(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
 				ttm_bo_get(bo);
@@ -165,6 +161,8 @@ static vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
 	}
 
 	if (bdev->driver->fault_reserve_notify) {
+		struct dma_fence *moving = dma_fence_get(bo->moving);
+
 		err = bdev->driver->fault_reserve_notify(bo);
 		switch (err) {
 		case 0:
@@ -177,6 +175,13 @@ static vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
 			ret = VM_FAULT_SIGBUS;
 			goto out_unlock;
 		}
+
+		if (bo->moving != moving) {
+			spin_lock(&bdev->glob->lru_lock);
+			ttm_bo_move_to_lru_tail(bo, NULL);
+			spin_unlock(&bdev->glob->lru_lock);
+		}
+		dma_fence_put(moving);
 	}
 
 	/*
@@ -291,7 +296,7 @@ static vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
 out_io_unlock:
 	ttm_mem_io_unlock(man);
 out_unlock:
-	ttm_bo_unreserve(bo);
+	reservation_object_unlock(bo->resv);
 	return ret;
 }