linux-kernel - [PATCH V2 3/5] virtio: introduce config op to synchronize vring callbacks

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Date:   Wed,  6 Apr 2022 16:35:36 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     mst@...hat.com, jasowang@...hat.com
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, maz@...nel.org, tglx@...utronix.de,
        peterz@...radead.org, sgarzare@...hat.com,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH V2 3/5] virtio: introduce config op to synchronize vring callbacks

This patch introduce a new virtio config ops to vring
callbacks. Transport specific method is required to call
synchornize_irq() on the IRQs. For the transport that doesn't provide
synchronize_vqs(), use synchornize_rcu() as a fallback.

Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: "Paul E. McKenney" <paulmck@...nel.org>
Cc: Marc Zyngier <maz@...nel.org>
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
 include/linux/virtio_config.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index b341dd62aa4d..08b73d9bbff2 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -57,6 +57,8 @@ 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_vqs: synchronize with the virtqueue callbacks.
+ *	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).
@@ -89,6 +91,7 @@ struct virtio_config_ops {
 			const char * const names[], const bool *ctx,
 			struct irq_affinity *desc);
 	void (*del_vqs)(struct virtio_device *);
+	void (*synchronize_vqs)(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);
@@ -217,6 +220,19 @@ int virtio_find_vqs_ctx(struct virtio_device *vdev, unsigned nvqs,
 				      desc);
 }
 
+/**
+ * virtio_synchronize_vqs - synchronize with virtqueue callbacks
+ * @vdev: the device
+ */
+static inline
+void virtio_synchronize_vqs(struct virtio_device *dev)
+{
+	if (dev->config->synchronize_vqs)
+		dev->config->synchronize_vqs(dev);
+	else
+		synchronize_rcu();
+}
+
 /**
  * virtio_device_ready - enable vq use in probe function
  * @vdev: the device
-- 
2.25.1