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@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Halil Pasic <pasic@linux.ibm.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Cc: Vineeth Vijayan <vneethv@linux.ibm.com>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: linux-s390@vger.kernel.org
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220527060120.20964-7-jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
index d35e7a3..c188e4f 100644 (file)
--- 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);