qemu: add multiqueue vhost-user support

This patch adds the support of queues attribute of the driver element
for vhost-user interface type. Example:

<interface type='vhostuser'>
      <mac address='52:54:00:ee:96:6d'/>
      <source type='unix' path='/tmp/vhost2.sock' mode='client'/>
      <model type='virtio'/>
      <driver queues='4'/>
</interface>

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1207692

Signed-off-by: Maxime Leroy <maxime.leroy@6wind.com>
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>

docs/formatdomain.html.in

@@ -4254,13 +4254,16 @@ qemu-kvm -net nic,model=? /dev/null
       </dd>
       <dt><code>queues</code></dt>
       <dd>
-        The optional <code>queues</code> attribute controls the number of
-        queues to be used for the<a href="http://www.linux-kvm.org/page/Multiqueue">
-        Multiqueue virtio-net</a> feature. If the interface has <code>&lt;model
-        type='virtio'/&gt;</code>, multiple packet processing queues can be
-        created; each queue will potentially be handled by a different
+        The optional <code>queues</code> attribute controls the number
+        of queues to be used for either
+        <a href="http://www.linux-kvm.org/page/Multiqueue"> Multiqueue
+        virtio-net</a> or <a href="#elementVhostuser">vhost-user</a> network
+        interfaces.  Use of multiple packet processing queues requires the
+        interface having the <code>&lt;model type='virtio'/&gt;</code>
+        element.  Each queue will potentially be handled by a different
         processor, resulting in much higher throughput.
-        <span class="since">Since 1.0.6 (QEMU and KVM only)</span>
+        <span class="since">virtio-net since 1.0.6 (QEMU and KVM only)</span>
+        <span class="since">vhost-user since 1.2.17 (QEMU and KVM only)</span>
       </dd>
       <dt><code>host</code> offloading options</dt>
       <dd>
@@ -4581,9 +4584,15 @@ qemu-kvm -net nic,model=? /dev/null
   &lt;devices&gt;
     &lt;interface type='vhostuser'&gt;
       &lt;mac address='52:54:00:3b:83:1a'/&gt;
-      &lt;source type='unix' path='/tmp/vhost.sock' mode='server'/&gt;
+      &lt;source type='unix' path='/tmp/vhost1.sock' mode='server'/&gt;
       &lt;model type='virtio'/&gt;
     &lt;/interface&gt;
+    &lt;interface type='vhostuser'&gt;
+      &lt;mac address='52:54:00:3b:83:1b'/&gt;
+      &lt;source type='unix' path='/tmp/vhost2.sock' mode='client'/&gt;
+      &lt;model type='virtio'/&gt;
+      &lt;driver queues='5'/&gt;
+    &lt;/interface&gt;
   &lt;/devices&gt;
   ...</pre>
 

src/qemu/qemu_command.c

@@ -8102,6 +8102,7 @@ qemuBuildVhostuserCommandLine(virCommandPtr cmd,
 {
     virBuffer chardev_buf = VIR_BUFFER_INITIALIZER;
     virBuffer netdev_buf = VIR_BUFFER_INITIALIZER;
+    unsigned int queues = net->driver.virtio.queues;
     char *nic = NULL;
 
     if (!qemuDomainSupportsNetdev(def, qemuCaps, net)) {
@@ -8139,13 +8140,24 @@ qemuBuildVhostuserCommandLine(virCommandPtr cmd,
     virBufferAsprintf(&netdev_buf, "type=vhost-user,id=host%s,chardev=char%s",
                       net->info.alias, net->info.alias);
 
+    if (queues > 1) {
+        if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_VHOSTUSER_MULTIQ)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("multi-queue is not supported for vhost-user "
+                             "with this QEMU binary"));
+            goto error;
+        }
+        virBufferAsprintf(&netdev_buf, ",queues=%u", queues);
+    }
+
     virCommandAddArg(cmd, "-chardev");
     virCommandAddArgBuffer(cmd, &chardev_buf);
 
     virCommandAddArg(cmd, "-netdev");
     virCommandAddArgBuffer(cmd, &netdev_buf);
 
-    if (!(nic = qemuBuildNicDevStr(def, net, -1, bootindex, 0, qemuCaps))) {
+    if (!(nic = qemuBuildNicDevStr(def, net, -1, bootindex,
+                                   queues, qemuCaps))) {
         virReportError(VIR_ERR_INTERNAL_ERROR,
                        "%s", _("Error generating NIC -device string"));
         goto error;

tests/qemuxml2argvdata/qemuxml2argv-net-vhostuser-multiq.args

@@ -0,0 +1,16 @@
+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
+/usr/bin/qemu -S -M \
+pc -m 214 -smp 1 -nographic -nodefaults -monitor unix:/tmp/test-monitor,server,nowait \
+-no-acpi -boot c -usb -hda /dev/HostVG/QEMUGuest1 \
+-chardev socket,id=charnet0,path=/tmp/vhost0.sock,server \
+-netdev type=vhost-user,id=hostnet0,chardev=charnet0 \
+-device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:ee:96:6b,bus=pci.0,addr=0x3 \
+-chardev socket,id=charnet1,path=/tmp/vhost1.sock \
+-netdev type=vhost-user,id=hostnet1,chardev=charnet1 \
+-device virtio-net-pci,netdev=hostnet1,id=net1,mac=52:54:00:ee:96:6c,bus=pci.0,addr=0x4 \
+-netdev socket,listen=:2015,id=hostnet2 \
+-device rtl8139,netdev=hostnet2,id=net2,mac=52:54:00:95:db:c0,bus=pci.0,addr=0x5 \
+-chardev socket,id=charnet3,path=/tmp/vhost2.sock \
+-netdev type=vhost-user,id=hostnet3,chardev=charnet3,queues=4 \
+-device virtio-net-pci,mq=on,vectors=10,netdev=hostnet3,id=net3,mac=52:54:00:ee:96:6d,\
+bus=pci.0,addr=0x6

tests/qemuxml2argvdata/qemuxml2argv-net-vhostuser-multiq.xml

@@ -0,0 +1,49 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <disk type='block' device='disk'>
+      <driver name='qemu' type='raw'/>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <interface type='vhostuser'>
+      <mac address='52:54:00:ee:96:6b'/>
+      <source type='unix' path='/tmp/vhost0.sock' mode='server'/>
+      <model type='virtio'/>
+    </interface>
+    <interface type='vhostuser'>
+      <mac address='52:54:00:ee:96:6c'/>
+      <source type='unix' path='/tmp/vhost1.sock' mode='client'/>
+      <model type='virtio'/>
+    </interface>
+    <interface type='server'>
+      <mac address='52:54:00:95:db:c0'/>
+      <source port='2015'/>
+      <model type='rtl8139'/>
+    </interface>
+    <interface type='vhostuser'>
+      <mac address='52:54:00:ee:96:6d'/>
+      <source type='unix' path='/tmp/vhost2.sock' mode='client'/>
+      <model type='virtio'/>
+      <driver queues='4'/>
+    </interface>
+    <memballoon model='none'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -980,6 +980,9 @@ mymain(void)
     DO_TEST("misc-uuid", QEMU_CAPS_NAME, QEMU_CAPS_UUID);
     DO_TEST_PARSE_ERROR("vhost_queues-invalid", NONE);
     DO_TEST("net-vhostuser", QEMU_CAPS_DEVICE, QEMU_CAPS_NETDEV);
+    DO_TEST("net-vhostuser-multiq",
+            QEMU_CAPS_DEVICE, QEMU_CAPS_NETDEV, QEMU_CAPS_VHOSTUSER_MULTIQ);
+    DO_TEST_FAILURE("net-vhostuser-multiq", QEMU_CAPS_DEVICE, QEMU_CAPS_NETDEV);
     DO_TEST("net-user", NONE);
     DO_TEST("net-virtio", NONE);
     DO_TEST("net-virtio-device",