drm/virtio: implement context init: track valid capabilities in a mask

The valid capability IDs are between 1 to 63, and defined in the
virtio gpu spec.  This is used for error checking the subsequent
patches.  We're currently only using 2 capability IDs, so this
should be plenty for the immediate future.
Signed-off-by: Gurchetan Singh <gurchetansingh@chromium.org>
Acked-by: Lingfeng Yang <lfy@google.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20210921232024.817-4-gurchetansingh@chromium.orgSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/virtio/virtgpu_drv.h

@@ -55,6 +55,8 @@
 #define STATE_OK 1
 #define STATE_ERR 2
 
+#define MAX_CAPSET_ID 63
+
 struct virtio_gpu_object_params {
 	unsigned long size;
 	bool dumb;
@@ -245,6 +247,7 @@ struct virtio_gpu_device {
 
 	struct virtio_gpu_drv_capset *capsets;
 	uint32_t num_capsets;
+	uint64_t capset_id_mask;
 	struct list_head cap_cache;
 
 	/* protects uuid state when exporting */

drivers/gpu/drm/virtio/virtgpu_kms.c

@@ -65,6 +65,7 @@ static void virtio_gpu_get_capsets(struct virtio_gpu_device *vgdev,
 				   int num_capsets)
 {
 	int i, ret;
+	bool invalid_capset_id = false;
 
 	vgdev->capsets = kcalloc(num_capsets,
 				 sizeof(struct virtio_gpu_drv_capset),
@@ -78,19 +79,34 @@ static void virtio_gpu_get_capsets(struct virtio_gpu_device *vgdev,
 		virtio_gpu_notify(vgdev);
 		ret = wait_event_timeout(vgdev->resp_wq,
 					 vgdev->capsets[i].id > 0, 5 * HZ);
-		if (ret == 0) {
+		/*
+		 * Capability ids are defined in the virtio-gpu spec and are
+		 * between 1 to 63, inclusive.
+		 */
+		if (!vgdev->capsets[i].id ||
+		    vgdev->capsets[i].id > MAX_CAPSET_ID)
+			invalid_capset_id = true;
+
+		if (ret == 0)
 			DRM_ERROR("timed out waiting for cap set %d\n", i);
+		else if (invalid_capset_id)
+			DRM_ERROR("invalid capset id %u", vgdev->capsets[i].id);
+
+		if (ret == 0 || invalid_capset_id) {
 			spin_lock(&vgdev->display_info_lock);
 			kfree(vgdev->capsets);
 			vgdev->capsets = NULL;
 			spin_unlock(&vgdev->display_info_lock);
 			return;
 		}
+
+		vgdev->capset_id_mask |= 1 << vgdev->capsets[i].id;
 		DRM_INFO("cap set %d: id %d, max-version %d, max-size %d\n",
 			 i, vgdev->capsets[i].id,
 			 vgdev->capsets[i].max_version,
 			 vgdev->capsets[i].max_size);
 	}
+
 	vgdev->num_capsets = num_capsets;
 }