Re: [PATCH V5 7/9] virtio: allow to unbreak virtqueue

On Wed, May 18, 2022 at 6:04 PM Cornelia Huck [off-list ref] wrote:

On Wed, May 18 2022, Jason Wang [off-list ref] wrote:

quoted

This patch allows the new introduced __virtio_break_device() to
unbreak the virtqueue.

Cc: Thomas Gleixner <redacted>
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 <redacted>
---
 drivers/virtio/virtio_ring.c | 21 +++++++++++++++++++++
 include/linux/virtio.h       |  1 +
 2 files changed, 22 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cfb028ca238e..5b7df7c455f0 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c

@@ -2397,6 +2397,27 @@ void virtio_break_device(struct virtio_device *dev)
 }
 EXPORT_SYMBOL_GPL(virtio_break_device);

+/*
+ * This should allow the device to be used by the driver. You may
+ * need to grab appropriate locks to flush. This should only be used

Hm, to flush what?

How about "to flush the write to vq->broken"?

quoted

+ * in some specific case e.g (probing and restoring). Driver should
+ * not call this directly.

Maybe "This function should only be called by the core, not directly by
the driver."?

Ok.

Thanks

quoted

+ */
+void __virtio_unbreak_device(struct virtio_device *dev)
+{
+     struct virtqueue *_vq;
+
+     spin_lock(&dev->vqs_list_lock);
+     list_for_each_entry(_vq, &dev->vqs, list) {
+             struct vring_virtqueue *vq = to_vvq(_vq);
+
+             /* Pairs with READ_ONCE() in virtqueue_is_broken(). */
+             WRITE_ONCE(vq->broken, false);
+     }
+     spin_unlock(&dev->vqs_list_lock);
+}
+EXPORT_SYMBOL_GPL(__virtio_unbreak_device);
+
 dma_addr_t virtqueue_get_desc_addr(struct virtqueue *_vq)
 {
      struct vring_virtqueue *vq = to_vvq(_vq);

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