drm/virtio: track whether or not a context has been initiated

Use an boolean variable to track whether a context has been
initiated.

v5: Fix possible race and sleep via mutex (olv)

Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Gurchetan Singh <gurchetansingh@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20200225000800.2966-3-gurchetansingh@chromium.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/virtio/virtgpu_drv.h

@@ -209,6 +209,8 @@ struct virtio_gpu_device {
 
 struct virtio_gpu_fpriv {
 	uint32_t ctx_id;
+	bool context_created;
+	struct mutex context_lock;
 };
 
 /* virtio_ioctl.c */

drivers/gpu/drm/virtio/virtgpu_ioctl.c

@@ -40,10 +40,18 @@ void virtio_gpu_create_context(struct drm_device *dev,
 	struct virtio_gpu_fpriv *vfpriv = file->driver_priv;
 	char dbgname[TASK_COMM_LEN];
 
+	mutex_lock(&vfpriv->context_lock);
+	if (vfpriv->context_created)
+		goto out_unlock;
+
 	get_task_comm(dbgname, current);
 	virtio_gpu_cmd_context_create(vgdev, vfpriv->ctx_id,
 				      strlen(dbgname), dbgname);
 	virtio_gpu_notify(vgdev);
+	vfpriv->context_created = true;
+
+out_unlock:
+	mutex_unlock(&vfpriv->context_lock);
 }
 
 static int virtio_gpu_map_ioctl(struct drm_device *dev, void *data,

drivers/gpu/drm/virtio/virtgpu_kms.c

@@ -258,6 +258,8 @@ int virtio_gpu_driver_open(struct drm_device *dev, struct drm_file *file)
 	if (!vfpriv)
 		return -ENOMEM;
 
+	mutex_init(&vfpriv->context_lock);
+
 	handle = ida_alloc(&vgdev->ctx_id_ida, GFP_KERNEL);
 	if (handle < 0) {
 		kfree(vfpriv);
@@ -281,6 +283,7 @@ void virtio_gpu_driver_postclose(struct drm_device *dev, struct drm_file *file)
 	vfpriv = file->driver_priv;
 
 	virtio_gpu_context_destroy(vgdev, vfpriv->ctx_id);
+	mutex_destroy(&vfpriv->context_lock);
 	kfree(vfpriv);
 	file->driver_priv = NULL;
 }