vhost: multiqueue support

This patch lets vhost support multiqueue. The idea is simple, just launching
multiple threads of vhost and let each of vhost thread processing a subset of
the virtqueues of the device. After this change each emulated device can have
multiple vhost threads as its backend.

To do this, a virtqueue index were introduced to record to first virtqueue that
will be handled by this vhost_net device. Based on this and nvqs, vhost could
calculate its relative index to setup vhost_net device.

Since we may have many vhost/net devices for a virtio-net device. The setting of
guest notifiers were moved out of the starting/stopping of a specific vhost
thread. The vhost_net_{start|stop}() were renamed to
vhost_net_{start|stop}_one(), and a new vhost_net_{start|stop}() were introduced
to configure the guest notifiers and start/stop all vhost/vhost_net devices.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 78 insertions, 8 deletions

diff --git a/hw/vhost_net.c b/hw/vhost_net.c
index d3a04ca..8693ac2 100644
--- a/hw/vhost_net.c
+++ b/hw/vhost_net.c
@@ -140,12 +140,21 @@ bool vhost_net_query(VHostNetState *net, VirtIODevice *dev)
     return vhost_dev_query(&net->dev, dev);
 }
 
-int vhost_net_start(struct vhost_net *net,
-                    VirtIODevice *dev)
+static int vhost_net_start_one(struct vhost_net *net,
+                               VirtIODevice *dev,
+                               int vq_index)
 {
     struct vhost_vring_file file = { };
     int r;
 
+    if (net->dev.started) {
+        return 0;
+    }
+
+    net->dev.nvqs = 2;
+    net->dev.vqs = net->vqs;
+    net->dev.vq_index = vq_index;
+
     r = vhost_dev_enable_notifiers(&net->dev, dev);
     if (r < 0) {
         goto fail_notifiers;
@@ -181,11 +190,15 @@ fail_notifiers:
     return r;
 }
 
-void vhost_net_stop(struct vhost_net *net,
-                    VirtIODevice *dev)
+static void vhost_net_stop_one(struct vhost_net *net,
+                               VirtIODevice *dev)
 {
     struct vhost_vring_file file = { .fd = -1 };
 
+    if (!net->dev.started) {
+        return;
+    }
+
     for (file.index = 0; file.index < net->dev.nvqs; ++file.index) {
         int r = ioctl(net->dev.control, VHOST_NET_SET_BACKEND, &file);
         assert(r >= 0);
@@ -195,6 +208,61 @@ void vhost_net_stop(struct vhost_net *net,
     vhost_dev_disable_notifiers(&net->dev, dev);
 }
 
+int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
+                    int total_queues)
+{
+    int r, i = 0;
+
+    if (!dev->binding->set_guest_notifiers) {
+        error_report("binding does not support guest notifiers\n");
+        r = -ENOSYS;
+        goto err;
+    }
+
+    for (i = 0; i < total_queues; i++) {
+        r = vhost_net_start_one(tap_get_vhost_net(ncs[i].peer), dev, i * 2);
+
+        if (r < 0) {
+            goto err;
+        }
+    }
+
+    r = dev->binding->set_guest_notifiers(dev->binding_opaque,
+                                          total_queues * 2,
+                                          true);
+    if (r < 0) {
+        error_report("Error binding guest notifier: %d\n", -r);
+        goto err;
+    }
+
+    return 0;
+
+err:
+    while (--i >= 0) {
+        vhost_net_stop_one(tap_get_vhost_net(ncs[i].peer), dev);
+    }
+    return r;
+}
+
+void vhost_net_stop(VirtIODevice *dev, NetClientState *ncs,
+                    int total_queues)
+{
+    int i, r;
+
+    r = dev->binding->set_guest_notifiers(dev->binding_opaque,
+                                          total_queues * 2,
+                                          false);
+    if (r < 0) {
+        fprintf(stderr, "vhost guest notifier cleanup failed: %d\n", r);
+        fflush(stderr);
+    }
+    assert(r >= 0);
+
+    for (i = 0; i < total_queues; i++) {
+        vhost_net_stop_one(tap_get_vhost_net(ncs[i].peer), dev);
+    }
+}
+
 void vhost_net_cleanup(struct vhost_net *net)
 {
     vhost_dev_cleanup(&net->dev);
@@ -224,13 +292,15 @@ bool vhost_net_query(VHostNetState *net, VirtIODevice *dev)
     return false;
 }
 
-int vhost_net_start(struct vhost_net *net,
-		    VirtIODevice *dev)
+int vhost_net_start(VirtIODevice *dev,
+                    NetClientState *ncs,
+                    int total_queues)
 {
     return -ENOSYS;
 }
-void vhost_net_stop(struct vhost_net *net,
-		    VirtIODevice *dev)
+void vhost_net_stop(VirtIODevice *dev,
+                    NetClientState *ncs,
+                    int total_queues)
 {
 }