[libvirt] i want to update the disk driver from ide to virtio, but fail , why ?

hi, ALL: my question description as follow: virsh dumpxml root-vsys_v2 > v2.xml , in the v2.xml has the following information: <disk type='file' device='disk'> <driver name='qemu' type='qcow2'/> <source file='/home/root-vsys_v2.qcow2'/> <backingStore/> <target dev='hda' bus='ide'/> // i want change the 'ide' to 'virtio', but fail <alias name='ide0-0-0'/> <address type='drive' controller='0' bus='0' target='0' unit='0'/> </disk> so i create a new xml name v2-new.xml ,it content is: <disk type='file' device='disk'> <driver name='qemu' type='qcow2'/> <source file='/home/root-vsys_v2.qcow2'/> <target dev='vda' bus='virtio'/> </disk> then run: virsh update-device root-vsys_v2 /root/v2-new.xml --live the result is: [root@NSG ~]# virsh update-device root-vsys_v2 /root/v2-new.xml --live error: Failed to update device from /root/v2-new.xml error: internal error: No device with bus 'virtio' and target 'vda' i read the source code for libvirt ,the log outprint at funcion: static int qemuDomainChangeDiskLive(virDomainObjPtr vm, virDomainDeviceDefPtr dev, virQEMUDriverPtr driver, bool force) { virDomainDiskDefPtr disk = dev->data.disk; virDomainDiskDefPtr orig_disk = NULL; virDomainDeviceDef oldDev = { .type = dev->type }; int ret = -1; if (!(orig_disk = virDomainDiskFindByBusAndDst(vm->def, disk->bus, disk->dst))) { virReportError(VIR_ERR_INTERNAL_ERROR, _("No device with bus '%s' and target '%s'"), virDomainDiskBusTypeToString(disk->bus), disk->dst); //the failure log is here, the vm->def has disk item :dev = hda, bus=ide ,and disk->bus = virtio disk->dst=vda, goto cleanup; } //the disk->bus and disk->dst can't in the vm->def ,so the api virDomainDiskFindByBusAndDst failed oldDev.data.disk = orig_disk; if (virDomainDefCompatibleDevice(vm->def, dev, &oldDev, VIR_DOMAIN_DEVICE_ACTION_UPDATE, true) < 0) goto cleanup; if (!qemuDomainDiskChangeSupported(disk, orig_disk)) goto cleanup; if (!virStorageSourceIsSameLocation(disk->src, orig_disk->src)) { /* Disk source can be changed only for removable devices */ if (disk->device != VIR_DOMAIN_DISK_DEVICE_CDROM && disk->device != VIR_DOMAIN_DISK_DEVICE_FLOPPY) { virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", _("disk source can be changed only in removable " "drives")); goto cleanup; } if (qemuDomainAttachDeviceDiskLive(driver, vm, dev, force) < 0) goto cleanup; } orig_disk->startupPolicy = dev->data.disk->startupPolicy; orig_disk->snapshot = dev->data.disk->snapshot; ret = 0; cleanup: return ret; } what reason lead the faiure ? is my v2-new.xml write error ? how to write the xml for virsh update-device ? i refer the link https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/... -------------------------- thanks ! thosmas.kuang