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    SubjectRe: [PATCH V5 6/9] virtio-ccw: implement synchronize_cbs()
    Date
    On Wed, May 18 2022, Jason Wang <jasowang@redhat.com> wrote:

    > 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 ans used in the synchronization method.

    s/ans/and/

    >
    > 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
    > Signed-off-by: Jason Wang <jasowang@redhat.com>
    > ---
    > drivers/s390/virtio/virtio_ccw.c | 27 +++++++++++++++++++++++++++
    > 1 file changed, 27 insertions(+)
    >
    > diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
    > index d35e7a3f7067..22d36594bcdd 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 +985,27 @@ 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) {
    > + /*
    > + * Synchronize with the vring_interrupt() with airq indicator

    Maybe

    /*
    * 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 {
    > + /*
    > + * Synchronize with the vring_interrupt() called by
    > + * virtio_ccw_int_handler().

    /*
    * 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 +1017,7 @@ 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 +1129,8 @@ static void virtio_ccw_int_handler(struct ccw_device *cdev,
    > vcdev->err = -EIO;
    > }
    > virtio_ccw_check_activity(vcdev, activity);
    > + /* Local interrupt should be disabled at this time */

    /* Interrupts are disabled here. */

    ?

    Interrupts enabled here would surely be a bug.

    > + 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. */

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