[PATCH v3 1/6] virtio_ccw: fix synchronize_cbs() after interrupt fallback

[Karl Mehltretter <kmehltretter@gmail.com>]

virtio_ccw_synchronize_cbs() assumes the device uses adapter interrupts
when vcdev->airq_info is not NULL. If registering adapter indicators
fails, virtio_ccw_find_vqs() falls back to classic interrupts but can
leave airq_info set.

With VIRTIO_HARDEN_NOTIFICATION enabled,
virtio_ccw_int_handler() invokes callbacks under vcdev->irq_lock.
synchronize_cbs() instead takes the indicator area lock, so it does
not synchronize with those callbacks.

Use vcdev->is_thinint, which the fallback clears, to select the lock.
Keep the airq_info check because is_thinint can be set before the
first find_vqs() call, when airq_info is still NULL.

Fixes: 3a232277c1ac ("virtio-ccw: implement synchronize_cbs()")
Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---
 drivers/s390/virtio/virtio_ccw.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
index bab6cad3fd5c..b90299205698 100644
--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c
@@ -1062,7 +1062,7 @@ 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) {
+	if (vcdev->is_thinint && info) {
 		/*
 		 * This device uses adapter interrupts: synchronize with
 		 * vring_interrupt() called by virtio_airq_handler()
-- 
2.39.5 (Apple Git-154)