Merge branch 'next' into for-linus

Prepare input updates for 5.20 (or 6.0) merge window.

1 files changed, 47 insertions, 15 deletions

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index dafdc7f48c01..b47c2e7ed0ee 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -23,8 +23,6 @@ struct virtio_shm_region {
  *       any of @get/@set, @get_status/@set_status, or @get_features/
  *       @finalize_features are NOT safe to be called from an atomic
  *       context.
- * @enable_cbs: enable the callbacks
- *      vdev: the virtio_device
  * @get: read the value of a configuration field
  *	vdev: the virtio_device
  *	offset: the offset of the configuration field
@@ -59,6 +57,11 @@ struct virtio_shm_region {
  *		include a NULL entry for vqs unused by driver
  *	Returns 0 on success or error status
  * @del_vqs: free virtqueues found by find_vqs().
+ * @synchronize_cbs: synchronize with the virtqueue callbacks (optional)
+ *      The function guarantees that all memory operations on the
+ *      queue before it are visible to the vring_interrupt() that is
+ *      called after it.
+ *      vdev: the virtio_device
  * @get_features: get the array of feature bits for this device.
  *	vdev: the virtio_device
  *	Returns the first 64 feature bits (all we currently need).
@@ -78,7 +81,6 @@ struct virtio_shm_region {
  */
 typedef void vq_callback_t(struct virtqueue *);
 struct virtio_config_ops {
-	void (*enable_cbs)(struct virtio_device *vdev);
 	void (*get)(struct virtio_device *vdev, unsigned offset,
 		    void *buf, unsigned len);
 	void (*set)(struct virtio_device *vdev, unsigned offset,
@@ -92,6 +94,7 @@ struct virtio_config_ops {
 			const char * const names[], const bool *ctx,
 			struct irq_affinity *desc);
 	void (*del_vqs)(struct virtio_device *);
+	void (*synchronize_cbs)(struct virtio_device *);
 	u64 (*get_features)(struct virtio_device *vdev);
 	int (*finalize_features)(struct virtio_device *vdev);
 	const char *(*bus_name)(struct virtio_device *vdev);
@@ -221,6 +224,25 @@ int virtio_find_vqs_ctx(struct virtio_device *vdev, unsigned nvqs,
 }
 
 /**
+ * virtio_synchronize_cbs - synchronize with virtqueue callbacks
+ * @vdev: the device
+ */
+static inline
+void virtio_synchronize_cbs(struct virtio_device *dev)
+{
+	if (dev->config->synchronize_cbs) {
+		dev->config->synchronize_cbs(dev);
+	} else {
+		/*
+		 * A best effort fallback to synchronize with
+		 * interrupts, preemption and softirq disabled
+		 * regions. See comment above synchronize_rcu().
+		 */
+		synchronize_rcu();
+	}
+}
+
+/**
  * virtio_device_ready - enable vq use in probe function
  * @vdev: the device
  *
@@ -233,10 +255,29 @@ void virtio_device_ready(struct virtio_device *dev)
 {
 	unsigned status = dev->config->get_status(dev);
 
-	if (dev->config->enable_cbs)
-                  dev->config->enable_cbs(dev);
+	WARN_ON(status & VIRTIO_CONFIG_S_DRIVER_OK);
 
-	BUG_ON(status & VIRTIO_CONFIG_S_DRIVER_OK);
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
+	/*
+	 * The virtio_synchronize_cbs() makes sure vring_interrupt()
+	 * will see the driver specific setup if it sees vq->broken
+	 * as false (even if the notifications come before DRIVER_OK).
+	 */
+	virtio_synchronize_cbs(dev);
+	__virtio_unbreak_device(dev);
+#endif
+	/*
+	 * The transport should ensure the visibility of vq->broken
+	 * before setting DRIVER_OK. See the comments for the transport
+	 * specific set_status() method.
+	 *
+	 * A well behaved device will only notify a virtqueue after
+	 * DRIVER_OK, this means the device should "see" the coherenct
+	 * memory write that set vq->broken as false which is done by
+	 * the driver when it sees DRIVER_OK, then the following
+	 * driver's vring_interrupt() will see vq->broken as false so
+	 * we won't lose any notification.
+	 */
 	dev->config->set_status(dev, status | VIRTIO_CONFIG_S_DRIVER_OK);
 }
 
@@ -565,13 +606,4 @@ static inline void virtio_cwrite64(struct virtio_device *vdev,
 		_r;							\
 	})
 
-#ifdef CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
-int arch_has_restricted_virtio_memory_access(void);
-#else
-static inline int arch_has_restricted_virtio_memory_access(void)
-{
-	return 0;
-}
-#endif /* CONFIG_ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS */
-
 #endif /* _LINUX_VIRTIO_CONFIG_H */