drm/vmwgfx: Fix the refuse_dma mode when using guest-backed objects

When we refuse DMA from system pages for whatever reason, we don't
handle that correctly when guest-backed objects was enabled.
Since guest-backed objects by definition require DMA to and from
system pages, disable all functionality that relies on them.
That basically amounts to 3D acceleration and screen targets.
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

drivers/gpu/drm/vmwgfx/vmwgfx_cmdbuf.c

@@ -1241,7 +1241,8 @@ int vmw_cmdbuf_set_pool_size(struct vmw_cmdbuf_man *man,
 		 * actually call into the already enabled manager, when
 		 * binding the MOB.
 		 */
-		if (!(dev_priv->capabilities & SVGA_CAP_DX))
+		if (!(dev_priv->capabilities & SVGA_CAP_DX) ||
+		    !dev_priv->has_mob)
 			return -ENOMEM;
 
 		ret = ttm_bo_create(&dev_priv->bdev, size, ttm_bo_type_device,

drivers/gpu/drm/vmwgfx/vmwgfx_drv.c

@@ -682,8 +682,10 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
 
 	ret = vmw_dma_select_mode(dev_priv);
 	if (unlikely(ret != 0)) {
-		DRM_INFO("Restricting capabilities due to IOMMU setup.\n");
+		DRM_INFO("Restricting capabilities since DMA not available.\n");
 		refuse_dma = true;
+		if (dev_priv->capabilities & SVGA_CAP_GBOBJECTS)
+			DRM_INFO("Disabling 3D acceleration.\n");
 	}
 
 	dev_priv->vram_size = vmw_read(dev_priv, SVGA_REG_VRAM_SIZE);
@@ -866,7 +868,7 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
 		dev_priv->has_gmr = false;
 	}
 
-	if (dev_priv->capabilities & SVGA_CAP_GBOBJECTS) {
+	if (dev_priv->capabilities & SVGA_CAP_GBOBJECTS && !refuse_dma) {
 		dev_priv->has_mob = true;
 		if (ttm_bo_init_mm(&dev_priv->bdev, VMW_PL_MOB,
 				   VMW_PL_MOB) != 0) {

drivers/gpu/drm/vmwgfx/vmwgfx_stdu.c

@@ -1888,7 +1888,7 @@ int vmw_kms_stdu_init_display(struct vmw_private *dev_priv)
 
 
 	/* Do nothing if Screen Target support is turned off */
-	if (!VMWGFX_ENABLE_SCREEN_TARGET_OTABLE)
+	if (!VMWGFX_ENABLE_SCREEN_TARGET_OTABLE || !dev_priv->has_mob)
 		return -ENOSYS;
 
 	if (!(dev_priv->capabilities & SVGA_CAP_GBOBJECTS))