[RFC 10/10] vhost: Route host->guest notification through shadow virtqueue

["Eugenio Pérez" <eperezma@redhat.com>]

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.h |  2 ++
 hw/virtio/vhost-shadow-virtqueue.c | 55 ++++++++++++++++++++++++++++++
 hw/virtio/vhost.c                  |  5 ++-
 3 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-virtqueue.h
index 466f8ae595..99a4e011fd 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -17,6 +17,8 @@
 
 typedef struct VhostShadowVirtqueue VhostShadowVirtqueue;
 
+EventNotifier *vhost_shadow_vq_get_call_notifier(VhostShadowVirtqueue *vq);
+
 bool vhost_shadow_vq_start_rcu(struct vhost_dev *dev,
                                VhostShadowVirtqueue *svq);
 void vhost_shadow_vq_stop_rcu(struct vhost_dev *dev,
diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index 908c36c66d..e2e0bfe325 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -53,6 +53,34 @@ static void handle_shadow_vq(VirtIODevice *vdev, VirtQueue *vq)
     vhost_shadow_vring_kick(svq);
 }
 
+static void vhost_handle_call(EventNotifier *n)
+{
+    VhostShadowVirtqueue *svq = container_of(n, VhostShadowVirtqueue,
+                                             call_notifier);
+
+    if (event_notifier_test_and_clear(n)) {
+        unsigned idx = virtio_queue_get_idx(svq->vdev, svq->vq);
+
+        /*
+         * Since QEMU has not add any descriptors, virtqueue code thinks its
+         * not needed to signal used. QEMU shadow virtqueue will take
+         * descriptor forwarding soon, so just invalidate used cache for now.
+         */
+        virtio_queue_invalidate_signalled_used(svq->vdev, idx);
+        virtio_notify_irqfd(svq->vdev, svq->vq);
+    }
+}
+
+/*
+ * Get the vhost call notifier of the shadow vq
+ * @vq Shadow virtqueue
+ */
+EventNotifier *vhost_shadow_vq_get_call_notifier(VhostShadowVirtqueue *vq)
+{
+    return &vq->call_notifier;
+}
+
+
 /*
  * Start shadow virtqueue operation.
  * @dev vhost device
@@ -70,6 +98,10 @@ bool vhost_shadow_vq_start_rcu(struct vhost_dev *dev,
         .index = idx,
         .fd = event_notifier_get_fd(&svq->kick_notifier),
     };
+    struct vhost_vring_file call_file = {
+        .index = idx,
+        .fd = event_notifier_get_fd(&svq->call_notifier),
+    };
     int r;
     bool ok;
 
@@ -88,6 +120,12 @@ bool vhost_shadow_vq_start_rcu(struct vhost_dev *dev,
         goto err_set_vring_kick;
     }
 
+    r = dev->vhost_ops->vhost_set_vring_call(dev, &call_file);
+    if (r != 0) {
+        error_report("Couldn't set call fd: %s", strerror(errno));
+        goto err_set_vring_call;
+    }
+
     event_notifier_set_handler(vq_host_notifier,
                                virtio_queue_host_notifier_read);
     virtio_queue_set_host_notifier_enabled(svq->vq, false);
@@ -95,6 +133,11 @@ bool vhost_shadow_vq_start_rcu(struct vhost_dev *dev,
 
     return true;
 
+err_set_vring_call:
+    kick_file.fd = event_notifier_get_fd(vq_host_notifier);
+    r = dev->vhost_ops->vhost_set_vring_kick(dev, &kick_file);
+    assert(r == 0);
+
 err_set_vring_kick:
     k->set_vq_handler(dev->vdev, idx, NULL);
 
@@ -129,6 +172,17 @@ void vhost_shadow_vq_stop_rcu(struct vhost_dev *dev,
     event_notifier_set_handler(vq_host_notifier, NULL);
     virtio_queue_set_host_notifier_enabled(svq->vq, true);
     k->set_vq_handler(svq->vdev, idx, NULL);
+
+    if (!dev->vqs[idx].notifier_is_masked) {
+        EventNotifier *e = vhost_shadow_vq_get_call_notifier(svq);
+
+        /* Restore vhost call */
+        vhost_virtqueue_mask(dev, svq->vdev, idx, false);
+        if (event_notifier_test_and_clear(e)) {
+            virtio_queue_invalidate_signalled_used(svq->vdev, idx);
+            virtio_notify_irqfd(svq->vdev, svq->vq);
+        }
+    }
 }
 
 /*
@@ -159,6 +213,7 @@ VhostShadowVirtqueue *vhost_shadow_vq_new(struct vhost_dev *dev, int idx)
         goto err_init_call_notifier;
     }
 
+    event_notifier_set_handler(&svq->call_notifier, vhost_handle_call);
     return g_steal_pointer(&svq);
 
 err_init_call_notifier:
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index bde688f278..5ad0990509 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -984,7 +984,6 @@ static int vhost_sw_live_migration_start(struct vhost_dev *dev)
             int stop_idx = idx;
             bool ok = vhost_shadow_vq_start_rcu(dev,
                                                 dev->shadow_vqs[idx]);
-
             if (!ok) {
                 while (--stop_idx >= 0) {
                     vhost_shadow_vq_stop_rcu(dev, dev->shadow_vqs[stop_idx]);
@@ -1610,6 +1609,10 @@ void vhost_virtqueue_mask(struct vhost_dev *hdev, VirtIODevice *vdev, int n,
     if (mask) {
         assert(vdev->use_guest_notifier_mask);
         file.fd = event_notifier_get_fd(&hdev->vqs[index].masked_notifier);
+    } else if (hdev->sw_lm_enabled) {
+        VhostShadowVirtqueue *svq = hdev->shadow_vqs[n];
+        EventNotifier *e = vhost_shadow_vq_get_call_notifier(svq);
+        file.fd = event_notifier_get_fd(e);
     } else {
         file.fd = event_notifier_get_fd(virtio_queue_get_guest_notifier(vvq));
     }
-- 
2.27.0