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: Lin Ma <lma@suse.com>
Signed-off-by: Ján Tomko <jtomko@redhat.com>

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);