[Qemu-devel] [PATCH 3/3] vhost-net: force guest_notifier_mask bypass in vhost-user case

[Didier Pallard]

Since guest_mask_notifier can not be used in vhost-user
mode due to buffering implied by unix control socket,
force VIRTIO_PCI_FLAG_USE_NOTIFIERMASK on virtio pci
of vhost-user interfaces, and send correct callfd
to the guest at vhost start.

Signed-off-by: Didier Pallard <didier.pall...@6wind.com>
Reviewed-by: Thibaut Collet <thibaut.col...@6wind.com>
---
 hw/net/vhost_net.c | 19 ++++++++++++++++++-
 hw/virtio/vhost.c  | 13 +++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 318c3e6..74318dc 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -36,9 +36,11 @@
 #include <stdio.h>
 
 #include "standard-headers/linux/virtio_ring.h"
+#include "hw/pci/pci.h"
 #include "hw/virtio/vhost.h"
 #include "hw/virtio/virtio-bus.h"
 #include "hw/virtio/virtio-access.h"
+#include "hw/virtio/virtio-pci.h"
 
 struct vhost_net {
     struct vhost_dev dev;
@@ -314,7 +316,22 @@ int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
     }
 
     for (i = 0; i < total_queues; i++) {
-        vhost_net_set_vq_index(get_vhost_net(ncs[i].peer), i * 2);
+        struct vhost_net *net= get_vhost_net(ncs[i].peer);
+        vhost_net_set_vq_index(net, i * 2);
+
+        /* Force VIRTIO_PCI_FLAG_USE_NOTIFIERMASK reset in vhost user case
+         * Must be done before set_guest_notifier call
+         */
+        if (net->nc->info->type == NET_CLIENT_OPTIONS_KIND_VHOST_USER) {
+            BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(dev)));
+            DeviceState *d = DEVICE(qbus->parent);
+            if (!strcmp(object_get_typename(OBJECT(d)), TYPE_VIRTIO_NET_PCI)) {
+                VirtIOPCIProxy *proxy = VIRTIO_PCI(d);
+
+                /* Force proxy to not use mask notifier */
+                proxy->flags &= ~VIRTIO_PCI_FLAG_USE_NOTIFIERMASK;
+            }
+        }
     }
 
     r = k->set_guest_notifiers(qbus->parent, total_queues * 2, true);
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index de29968..7a4c1d3 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -854,8 +854,21 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
     /* Clear and discard previous events if any. */
     event_notifier_test_and_clear(&vq->masked_notifier);
 
+    /* If vhost user, register now the call eventfd, guest_notifier_mask
+     * function is not used anymore
+     */
+    if (dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER) {
+        file.fd = event_notifier_get_fd(virtio_queue_get_guest_notifier(vvq));
+        r = dev->vhost_ops->vhost_set_vring_call(dev, &file);
+        if (r) {
+            r = -errno;
+            goto fail_call;
+        }
+    }
+
     return 0;
 
+fail_call:
 fail_kick:
 fail_alloc:
     cpu_physical_memory_unmap(vq->ring, virtio_queue_get_ring_size(vdev, idx),
-- 
2.1.4