qemuBuildHostNetStr: Support VIR_DOMAIN_NET_TYPE_VHOSTUSER

https://bugzilla.redhat.com/show_bug.cgi?id=1366505

So far, this function lacked support for
VIR_DOMAIN_NET_TYPE_VHOSTUSER leaving callers to hack around the
problem by constructing the command line on their own. This is
not ideal as it blocks hot plug support.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_command.c

@@ -3733,7 +3733,13 @@ qemuBuildHostNetStr(virDomainNetDefPtr net,
         return NULL;
 
     case VIR_DOMAIN_NET_TYPE_VHOSTUSER:
-        /* Unsupported yet. */
+        virBufferAsprintf(&buf, "vhost-user%cchardev=char%s",
+                          type_sep,
+                          net->info.alias);
+        type_sep = ',';
+        if (net->driver.virtio.queues > 1)
+            virBufferAsprintf(&buf, ",queues=%u",
+                              net->driver.virtio.queues);
         break;
 
     case VIR_DOMAIN_NET_TYPE_LAST:
@@ -7791,7 +7797,7 @@ qemuBuildVhostuserCommandLine(virQEMUDriverPtr driver,
 {
     virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
     char *chardev = NULL;
-    virBuffer netdev_buf = VIR_BUFFER_INITIALIZER;
+    char *netdev = NULL;
     unsigned int queues = net->driver.virtio.queues;
     char *nic = NULL;
 
@@ -7828,25 +7834,27 @@ qemuBuildVhostuserCommandLine(virQEMUDriverPtr driver,
         goto error;
     }
 
-    virBufferAsprintf(&netdev_buf, "vhost-user,id=host%s,chardev=char%s",
-                      net->info.alias, net->info.alias);
-
-    if (queues > 1) {
-        if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_VHOSTUSER_MULTIQUEUE)) {
-            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);
+    if (queues > 1 &&
+        !virQEMUCapsGet(qemuCaps, QEMU_CAPS_VHOSTUSER_MULTIQUEUE)) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("multi-queue is not supported for vhost-user "
+                         "with this QEMU binary"));
+        goto error;
     }
 
+    if (!(netdev = qemuBuildHostNetStr(net, driver,
+                                       ',', -1,
+                                       NULL, 0, NULL, 0)))
+        goto error;
+
+
     virCommandAddArg(cmd, "-chardev");
     virCommandAddArg(cmd, chardev);
     VIR_FREE(chardev);
 
     virCommandAddArg(cmd, "-netdev");
-    virCommandAddArgBuffer(cmd, &netdev_buf);
+    virCommandAddArg(cmd, netdev);
+    VIR_FREE(netdev);
 
     if (!(nic = qemuBuildNicDevStr(def, net, -1, bootindex,
                                    queues, qemuCaps))) {
@@ -7863,8 +7871,8 @@ qemuBuildVhostuserCommandLine(virQEMUDriverPtr driver,
 
  error:
     virObjectUnref(cfg);
+    VIR_FREE(netdev);
     VIR_FREE(chardev);
-    virBufferFreeAndReset(&netdev_buf);
     VIR_FREE(nic);
 
     return -1;

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

@@ -20,17 +20,17 @@ QEMU_AUDIO_DRV=none \
 -drive file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-0 \
 -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
 -chardev socket,id=charnet0,path=/tmp/vhost0.sock,server \
--netdev vhost-user,id=hostnet0,chardev=charnet0 \
+-netdev vhost-user,chardev=charnet0,id=hostnet0 \
 -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 vhost-user,id=hostnet1,chardev=charnet1 \
+-netdev vhost-user,chardev=charnet1,id=hostnet1 \
 -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 vhost-user,id=hostnet3,chardev=charnet3,queues=4 \
+-netdev vhost-user,chardev=charnet3,queues=4,id=hostnet3 \
 -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.args

@@ -20,11 +20,11 @@ QEMU_AUDIO_DRV=none \
 -drive file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-0 \
 -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
 -chardev socket,id=charnet0,path=/tmp/vhost0.sock,server \
--netdev vhost-user,id=hostnet0,chardev=charnet0 \
+-netdev vhost-user,chardev=charnet0,id=hostnet0 \
 -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 vhost-user,id=hostnet1,chardev=charnet1 \
+-netdev vhost-user,chardev=charnet1,id=hostnet1 \
 -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 \