qemu: Support multiqueue virtio-blk

qemu 2.7.0 introduces multiqueue virtio-blk(commit 2f27059).
This patch introduces a new attribute "queues". An example of
the XML:

<disk type='file' device='disk'>
  <driver name='qemu' type='qcow2' queues='4'/>

The corresponding QEMU command line:

-device virtio-blk-pci,scsi=off,num-queues=4,id=virtio-disk0
Signed-off-by: NLin Ma <lma@suse.com>
Signed-off-by: NJán Tomko <jtomko@redhat.com>

docs/formatdomain.html.in

@@ -2397,7 +2397,7 @@
     <target dev='vdc' bus='virtio'/>
   </disk>
   <disk type='file' device='disk'>
-    <driver name='qemu' type='qcow2'/>
+    <driver name='qemu' type='qcow2' queues='4'/>
     <source file='/var/lib/libvirt/images/domain.qcow'/>
     <backingStore type='file'>
       <format type='qcow2'/>
@@ -3057,6 +3057,10 @@
             <code>bus</code> and "pci" or "ccw" <code>address</code> types.
             <span class='since'>Since 1.2.8 (QEMU 2.1)</span>
           </li>
+          <li>
+            The optional <code>queues</code> attribute specifies the number of
+            virt queues for virtio-blk. (<span class="since">Since 3.9.0</span>)
+          </li>
           <li>
           For virtio disks,
           <a href="#elementsVirtio">Virtio-specific options</a> can also be

docs/schemas/domaincommon.rng

@@ -1811,6 +1811,11 @@
       <optional>
         <ref name="detect_zeroes"/>
       </optional>
+      <optional>
+        <attribute name='queues'>
+          <ref name="positiveInteger"/>
+        </attribute>
+      </optional>
       <ref name="virtioOptions"/>
       <empty/>
     </element>

src/conf/domain_conf.c

@@ -5113,6 +5113,13 @@ virDomainDiskDefValidate(const virDomainDiskDef *disk)
         return -1;
     }
 
+    if (disk->queues && disk->bus != VIR_DOMAIN_DISK_BUS_VIRTIO) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("queues attribute in disk driver element is only "
+                         "supported by virtio-blk"));
+        return -1;
+    }
+
     return 0;
 }
 
@@ -8776,6 +8783,15 @@ virDomainDiskDefDriverParseXML(virDomainDiskDefPtr def,
     }
     VIR_FREE(tmp);
 
+    if ((tmp = virXMLPropString(cur, "queues")) &&
+        virStrToLong_uip(tmp, NULL, 10, &def->queues) < 0) {
+        virReportError(VIR_ERR_XML_ERROR,
+                       _("'queues' attribute must be positive number: %s"),
+                       tmp);
+        goto cleanup;
+    }
+    VIR_FREE(tmp);
+
     ret = 0;
 
  cleanup:
@@ -22030,6 +22046,8 @@ virDomainDiskDefFormat(virBufferPtr buf,
         virBufferAsprintf(&driverBuf, " iothread='%u'", def->iothread);
     if (def->detect_zeroes)
         virBufferAsprintf(&driverBuf, " detect_zeroes='%s'", detect_zeroes);
+    if (def->queues)
+        virBufferAsprintf(&driverBuf, " queues='%u'", def->queues);
 
     virDomainVirtioOptionsFormat(&driverBuf, def->virtio);
 

src/conf/domain_conf.h

@@ -668,6 +668,7 @@ struct _virDomainDiskDef {
     unsigned int iothread; /* unused = 0, > 0 specific thread # */
     int detect_zeroes; /* enum virDomainDiskDetectZeroes */
     char *domain_name; /* backend domain name */
+    unsigned int queues;
     virDomainVirtioOptionsPtr virtio;
 };
 

src/qemu/qemu_command.c

@@ -2083,6 +2083,17 @@ qemuBuildDriveDevStr(const virDomainDef *def,
                               ? "on" : "off");
         }
 
+        if (disk->queues) {
+            if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_VIRTIO_BLK_NUM_QUEUES)) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                               _("num-queues property isn't supported by this "
+                                 "QEMU binary"));
+                goto error;
+            }
+
+            virBufferAsprintf(&opt, ",num-queues=%u", disk->queues);
+        }
+
         if (qemuBuildVirtioOptionsStr(&opt, disk->virtio, qemuCaps) < 0)
             goto error;
 

src/qemu/qemu_domain.h

@@ -883,6 +883,9 @@ bool qemuDomainVcpuHotplugIsInOrder(virDomainDefPtr def)
 void qemuDomainVcpuPersistOrder(virDomainDefPtr def)
     ATTRIBUTE_NONNULL(1);
 
+int qemuDomainDefValidateDisk(const virDomainDiskDef *disk,
+                              virQEMUCapsPtr qemuCaps);
+
 int qemuDomainCheckMonitor(virQEMUDriverPtr driver,
                            virDomainObjPtr vm,
                            qemuDomainAsyncJob asyncJob);

tests/qemuxml2argvdata/qemuxml2argv-disk-virtio-drive-queues.args

+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-i686 \
+-name QEMUGuest1 \
+-S \
+-M pc \
+-m 214 \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-nographic \
+-nodefaults \
+-chardev socket,id=charmonitor,path=/tmp/lib/domain--1-QEMUGuest1/monitor.sock,\
+server,nowait \
+-mon chardev=charmonitor,id=monitor,mode=readline \
+-no-acpi \
+-boot c \
+-usb \
+-drive file=/tmp/data.img,format=raw,if=none,id=drive-virtio-disk0 \
+-device virtio-blk-pci,num-queues=4,bus=pci.0,addr=0x3,\
+drive=drive-virtio-disk0,id=virtio-disk0

tests/qemuxml2argvdata/qemuxml2argv-disk-virtio-drive-queues.xml

+<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-system-i686</emulator>
+    <disk type='file' device='disk'>
+      <driver name='qemu' type='raw' queues='4'/>
+      <source file='/tmp/data.img'/>
+      <target dev='vda' bus='virtio'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
+    </disk>
+    <controller type='usb' index='0'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
+    </controller>
+    <controller type='ide' index='0'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
+    </controller>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='none'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -892,6 +892,8 @@ mymain(void)
             QEMU_CAPS_VIRTIO_CCW, QEMU_CAPS_VIRTIO_S390);
     DO_TEST("disk-order",
             QEMU_CAPS_DRIVE_BOOT, QEMU_CAPS_VIRTIO_BLK_SCSI);
+    DO_TEST("disk-virtio-drive-queues",
+            QEMU_CAPS_VIRTIO_BLK_NUM_QUEUES);
     DO_TEST("disk-drive-boot-disk",
             QEMU_CAPS_DRIVE_BOOT);
     DO_TEST("disk-drive-boot-cdrom",

tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-virtio-drive-queues.xml

+<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-system-i686</emulator>
+    <disk type='file' device='disk'>
+      <driver name='qemu' type='raw' queues='4'/>
+      <source file='/tmp/data.img'/>
+      <target dev='vda' bus='virtio'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
+    </disk>
+    <controller type='usb' index='0'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
+    </controller>
+    <controller type='ide' index='0'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
+    </controller>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='none'/>
+  </devices>
+</domain>

tests/qemuxml2xmltest.c

@@ -449,6 +449,7 @@ mymain(void)
     DO_TEST("disk-usb-device", NONE);
     DO_TEST("disk-virtio", NONE);
     DO_TEST("floppy-drive-fat", NONE);
+    DO_TEST("disk-virtio-drive-queues", QEMU_CAPS_VIRTIO_BLK_NUM_QUEUES);
     DO_TEST("disk-drive-boot-disk", NONE);
     DO_TEST("disk-drive-boot-cdrom", NONE);
     DO_TEST("disk-drive-error-policy-stop", NONE);