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<p class="MsoNormal">Hello all,<o:p></o:p></p>
<p class="MsoNormal"> I find this curious behavior that libvirt will automatically insert a USB controller and a memballoon virtio driver into the domain’s XML, when defineXML is called. IOW, the original XML did not have these 2 devices but they are present
right after defineXML is called. Why should libvirt add a USB controller?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">DETAILS:<o:p></o:p></p>
<p class="MsoNormal">Here is a little Python snippet to show that behavior:<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">import libvirt<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">conn = libvirt.open('qemu:///system')<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">xml_list = open('/tmp/vm.xml', "r").readlines()<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">in_xml = ''.join(xml_list)
</span><span style="font-family:Wingdings">ß</span><span style="font-family:"Courier New"">
</span><b><span style="color:red">This XML string does not have a USB or a memballoon</span></b><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">dom = conn.defineXML(in_xml)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">out_xml = dom.XMLDesc()
</span><span style="font-family:Wingdings">ß</span><span style="font-family:"Courier New"">
</span><b><span style="color:red">But this XML string does!</span></b><span style="font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">print out_xml</span><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The file /tmp/vm.xml does not have a memballoon or a USB device. Neither, of course, does in_xml string. But out_xml has:<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> <controller type='usb' index='0'><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> </controller><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> <memballoon model='virtio'><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""> </memballoon><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I don’t see anything in libvirt.conf that explains this. This is libvirt version: 1.2.8, package: 16.el7_1.5 (Red Hat, Inc....). The host is RHEL 7.1.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The memballoon part is understandable once I found: <a href="https://www.redhat.com/archives/libvir-list/2010-August/msg00132.html">
https://www.redhat.com/archives/libvir-list/2010-August/msg00132.html</a> <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">However, why should libvirt add a USB controller gratuitously? Is this controllable from the conf file?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Cheers,<o:p></o:p></p>
<p class="MsoNormal">Sundar<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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