[RFC PATCH v4 17/20] vhost: Use VRING_AVAIL_F_NO_INTERRUPT at device call on shadow virtqueue

[Eugenio Pérez]

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.c 
b/hw/virtio/vhost-shadow-virtqueue.c
index 775f8d36a0..2fd0bab75d 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -60,6 +60,9 @@ typedef struct VhostShadowVirtqueue {
 
     /* Next head to consume from device */
     uint16_t used_idx;
+
+    /* Cache for the exposed notification flag */
+    bool notification;
 } VhostShadowVirtqueue;
 
 /* If the device is using some of these, SVQ cannot communicate */
@@ -105,6 +108,24 @@ bool vhost_svq_valid_device_features(uint64_t 
*dev_features)
     return r;
 }
 
+static void vhost_svq_set_notification(VhostShadowVirtqueue *svq, bool enable)
+{
+    uint16_t notification_flag;
+
+    if (svq->notification == enable) {
+        return;
+    }
+
+    notification_flag = cpu_to_le16(VRING_AVAIL_F_NO_INTERRUPT);
+
+    svq->notification = enable;
+    if (enable) {
+        svq->vring.avail->flags &= ~notification_flag;
+    } else {
+        svq->vring.avail->flags |= notification_flag;
+    }
+}
+
 static void vhost_vring_write_descs(VhostShadowVirtqueue *svq,
                                     const struct iovec *iovec,
                                     size_t num, bool more_descs, bool write)
@@ -273,7 +294,7 @@ static void vhost_svq_handle_call_no_test(EventNotifier *n)
     do {
         unsigned i = 0;
 
-        /* TODO: Use VRING_AVAIL_F_NO_INTERRUPT */
+        vhost_svq_set_notification(svq, false);
         while (true) {
             g_autofree VirtQueueElement *elem = vhost_svq_get_buf(svq);
             if (!elem) {
@@ -286,6 +307,7 @@ static void vhost_svq_handle_call_no_test(EventNotifier *n)
 
         virtqueue_flush(vq, i);
         event_notifier_set(&svq->guest_call_notifier);
+        vhost_svq_set_notification(svq, true);
     } while (vhost_svq_more_used(svq));
 }
 
-- 
2.27.0