4 files changed, 62 insertions, 10 deletions

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 8d5a646ebe6a..07e02c4bf5a8 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -151,7 +151,7 @@ static void ttm_bo_release_list(struct kref *list_kref)
         atomic_dec(&bo->glob->bo_count);
         if (bo->resv == &bo->ttm_resv)
                 reservation_object_fini(&bo->ttm_resv);
-
+        mutex_destroy(&bo->wu_mutex);
         if (bo->destroy)
                 bo->destroy(bo);
         else {
@@ -1123,6 +1123,7 @@ int ttm_bo_init(struct ttm_bo_device *bdev,
         INIT_LIST_HEAD(&bo->ddestroy);
         INIT_LIST_HEAD(&bo->swap);
         INIT_LIST_HEAD(&bo->io_reserve_lru);
+        mutex_init(&bo->wu_mutex);
         bo->bdev = bdev;
         bo->glob = bdev->glob;
         bo->type = type;
@@ -1704,3 +1705,35 @@ void ttm_bo_swapout_all(struct ttm_bo_device *bdev)
                 ;
 }
 EXPORT_SYMBOL(ttm_bo_swapout_all);
+
+/**
+ * ttm_bo_wait_unreserved - interruptible wait for a buffer object to become
+ * unreserved
+ *
+ * @bo: Pointer to buffer
+ */
+int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo)
+{
+        int ret;
+
+        /*
+         * In the absense of a wait_unlocked API,
+         * Use the bo::wu_mutex to avoid triggering livelocks due to
+         * concurrent use of this function. Note that this use of
+         * bo::wu_mutex can go away if we change locking order to
+         * mmap_sem -> bo::reserve.
+         */
+        ret = mutex_lock_interruptible(&bo->wu_mutex);
+        if (unlikely(ret != 0))
+                return -ERESTARTSYS;
+        if (!ww_mutex_is_locked(&bo->resv->lock))
+                goto out_unlock;
+        ret = ttm_bo_reserve_nolru(bo, true, false, false, NULL);
+        if (unlikely(ret != 0))
+                goto out_unlock;
+        ww_mutex_unlock(&bo->resv->lock);
+
+out_unlock:
+        mutex_unlock(&bo->wu_mutex);
+        return ret;
+}
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index 4834c463c38b..15b86a94949d 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -350,10 +350,13 @@ int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
                 goto out2;
 
         /*
-         * Move nonexistent data. NOP.
+         * Don't move nonexistent data. Clear destination instead.
          */
-        if (old_iomap == NULL && ttm == NULL)
+        if (old_iomap == NULL &&
+            (ttm == NULL || ttm->state == tt_unpopulated)) {
+                memset_io(new_iomap, 0, new_mem->num_pages*PAGE_SIZE);
                 goto out2;
+        }
 
         /*
          * TTM might be null for moves within the same region.
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index ac617f3ecd0c..b249ab9b1eb2 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -107,13 +107,28 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
         /*
          * Work around locking order reversal in fault / nopfn
          * between mmap_sem and bo_reserve: Perform a trylock operation
-         * for reserve, and if it fails, retry the fault after scheduling.
+         * for reserve, and if it fails, retry the fault after waiting
+         * for the buffer to become unreserved.
          */
-
-        ret = ttm_bo_reserve(bo, true, true, false, 0);
+        ret = ttm_bo_reserve(bo, true, true, false, NULL);
         if (unlikely(ret != 0)) {
-                if (ret == -EBUSY)
-                        set_need_resched();
+                if (ret != -EBUSY)
+                        return VM_FAULT_NOPAGE;
+
+                if (vmf->flags & FAULT_FLAG_ALLOW_RETRY) {
+                        if (!(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
+                                up_read(&vma->vm_mm->mmap_sem);
+                                (void) ttm_bo_wait_unreserved(bo);
+                        }
+
+                        return VM_FAULT_RETRY;
+                }
+
+                /*
+                 * If we'd want to change locking order to
+                 * mmap_sem -> bo::reserve, we'd use a blocking reserve here
+                 * instead of retrying the fault...
+                 */
                 return VM_FAULT_NOPAGE;
         }
 
@@ -123,7 +138,6 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
                 case 0:
                         break;
                 case -EBUSY:
-                        set_need_resched();
                 case -ERESTARTSYS:
                         retval = VM_FAULT_NOPAGE;
                         goto out_unlock;
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 751eaffbf0d5..ee127ec33c60 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -169,6 +169,7 @@ struct ttm_tt;
  * @offset: The current GPU offset, which can have different meanings
  * depending on the memory type. For SYSTEM type memory, it should be 0.
  * @cur_placement: Hint of current placement.
+ * @wu_mutex: Wait unreserved mutex.
  *
  * Base class for TTM buffer object, that deals with data placement and CPU
  * mappings. GPU mappings are really up to the driver, but for simpler GPUs
@@ -250,6 +251,7 @@ struct ttm_buffer_object {
 
         struct reservation_object *resv;
         struct reservation_object ttm_resv;
+        struct mutex wu_mutex;
 };
 
 /**
@@ -702,5 +704,5 @@ extern ssize_t ttm_bo_io(struct ttm_bo_device *bdev, struct file *filp,
                          size_t count, loff_t *f_pos, bool write);
 
 extern void ttm_bo_swapout_all(struct ttm_bo_device *bdev);
-
+extern int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo);
 #endif