linux-kernel - [PATCH V6 6/9] virtio-ccw: implement synchronize

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Date:   Fri, 27 May 2022 14:01:17 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     mst@...hat.com, jasowang@...hat.com,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, peterz@...radead.org, paulmck@...nel.org,
        maz@...nel.org, pasic@...ux.ibm.com, cohuck@...hat.com,
        eperezma@...hat.com, lulu@...hat.com, sgarzare@...hat.com,
        xuanzhuo@...ux.alibaba.com,
        Vineeth Vijayan <vneethv@...ux.ibm.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        linux-s390@...r.kernel.org
Subject: [PATCH V6 6/9] virtio-ccw: implement synchronize_cbs()

This patch tries to implement the synchronize_cbs() for ccw. For the
vring_interrupt() that is called via virtio_airq_handler(), the
synchronization is simply done via the airq_info's lock. For the
vring_interrupt() that is called via virtio_ccw_int_handler(), a per
device rwlock is introduced and used in the synchronization method.

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>
Cc: Halil Pasic <pasic@...ux.ibm.com>
Cc: Cornelia Huck <cohuck@...hat.com>
Cc: Vineeth Vijayan <vneethv@...ux.ibm.com>
Cc: Peter Oberparleiter <oberpar@...ux.ibm.com>
Cc: linux-s390@...r.kernel.org
Reviewed-by: Halil Pasic <pasic@...ux.ibm.com>
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
 drivers/s390/virtio/virtio_ccw.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
index d35e7a3f7067..c188e4f20ca3 100644
--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c
@@ -62,6 +62,7 @@ struct virtio_ccw_device {
 	unsigned int revision; /* Transport revision */
 	wait_queue_head_t wait_q;
 	spinlock_t lock;
+	rwlock_t irq_lock;
 	struct mutex io_lock; /* Serializes I/O requests */
 	struct list_head virtqueues;
 	bool is_thinint;
@@ -984,6 +985,30 @@ static const char *virtio_ccw_bus_name(struct virtio_device *vdev)
 	return dev_name(&vcdev->cdev->dev);
 }
 
+static void virtio_ccw_synchronize_cbs(struct virtio_device *vdev)
+{
+	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
+	struct airq_info *info = vcdev->airq_info;
+
+	if (info) {
+		/*
+		 * This device uses adapter interrupts: synchronize with
+		 * vring_interrupt() called by virtio_airq_handler()
+		 * via the indicator area lock.
+		 */
+		write_lock_irq(&info->lock);
+		write_unlock_irq(&info->lock);
+	} else {
+		/* This device uses classic interrupts: synchronize
+		 * with vring_interrupt() called by
+		 * virtio_ccw_int_handler() via the per-device
+		 * irq_lock
+		 */
+		write_lock_irq(&vcdev->irq_lock);
+		write_unlock_irq(&vcdev->irq_lock);
+	}
+}
+
 static const struct virtio_config_ops virtio_ccw_config_ops = {
 	.get_features = virtio_ccw_get_features,
 	.finalize_features = virtio_ccw_finalize_features,
@@ -995,6 +1020,7 @@ static const struct virtio_config_ops virtio_ccw_config_ops = {
 	.find_vqs = virtio_ccw_find_vqs,
 	.del_vqs = virtio_ccw_del_vqs,
 	.bus_name = virtio_ccw_bus_name,
+	.synchronize_cbs = virtio_ccw_synchronize_cbs,
 };
 
 
@@ -1106,6 +1132,8 @@ static void virtio_ccw_int_handler(struct ccw_device *cdev,
 			vcdev->err = -EIO;
 	}
 	virtio_ccw_check_activity(vcdev, activity);
+	/* Interrupts are disabled here */
+	read_lock(&vcdev->irq_lock);
 	for_each_set_bit(i, indicators(vcdev),
 			 sizeof(*indicators(vcdev)) * BITS_PER_BYTE) {
 		/* The bit clear must happen before the vring kick. */
@@ -1114,6 +1142,7 @@ static void virtio_ccw_int_handler(struct ccw_device *cdev,
 		vq = virtio_ccw_vq_by_ind(vcdev, i);
 		vring_interrupt(0, vq);
 	}
+	read_unlock(&vcdev->irq_lock);
 	if (test_bit(0, indicators2(vcdev))) {
 		virtio_config_changed(&vcdev->vdev);
 		clear_bit(0, indicators2(vcdev));
@@ -1284,6 +1313,7 @@ static int virtio_ccw_online(struct ccw_device *cdev)
 	init_waitqueue_head(&vcdev->wait_q);
 	INIT_LIST_HEAD(&vcdev->virtqueues);
 	spin_lock_init(&vcdev->lock);
+	rwlock_init(&vcdev->irq_lock);
 	mutex_init(&vcdev->io_lock);
 
 	spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
-- 
2.25.1