Add libvirt config classes for handling capabilities XML doc

Libvirt exposes the host/hypervisor features using an XML
schema known as "capabilities". Currently the libvirt driver
code just parses this in an adhoc manner using xpath queries.

This change provides a handful of classes LibvirtConfigCaps,
LibvirtConfigCapsHost and LibvirtConfigCapsGuest for maintaining
an object based representation of the capabilities. The
LibvirtConfigCapsHost class also uses the existing LibvirtConfigCPU
class

Fixes: bug #1003373
Implements: blueprint libvirt-xml-cpu-model
Change-Id: Ie962c6378b0da09eddc75983d4824a226ed1c25e
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

nova/tests/test_libvirt_config.py

@@ -59,6 +59,41 @@ def test_config_parse(self):
         obj.parse_str(inxml)
 
 
+class LibvirtConfigCapsTest(LibvirtConfigBaseTest):
+
+    def test_config_host(self):
+        xmlin = """
+        <capabilities>
+          <host>
+            <cpu>
+              <arch>x86_64</arch>
+              <model>Opteron_G3</model>
+              <vendor>AMD</vendor>
+              <topology sockets='1' cores='4' threads='1'/>
+              <feature name='ibs'/>
+              <feature name='osvw'/>
+            </cpu>
+          </host>
+          <guest>
+            <os_type>hvm</os_type>
+            <arch name='x86_64'/>
+          </guest>
+          <guest>
+            <os_type>hvm</os_type>
+            <arch name='i686'/>
+          </guest>
+        </capabilities>"""
+
+        obj = config.LibvirtConfigCaps()
+        obj.parse_str(xmlin)
+
+        self.assertEqual(type(obj.host), config.LibvirtConfigCapsHost)
+
+        xmlout = obj.to_xml()
+
+        self.assertXmlEqual(xmlin, xmlout)
+
+
 class LibvirtConfigGuestTimerTest(LibvirtConfigBaseTest):
     def test_config_platform(self):
         obj = config.LibvirtConfigGuestTimer()

nova/virt/libvirt/config.py

@@ -67,6 +67,94 @@ def to_xml(self, pretty_print=True):
         return xml_str
 
 
+class LibvirtConfigCaps(LibvirtConfigObject):
+
+    def __init__(self, **kwargs):
+        super(LibvirtConfigCaps, self).__init__(root_name="capabilities",
+                                                **kwargs)
+        self.host = None
+        self.guests = []
+
+    def parse_dom(self, xmldoc):
+        super(LibvirtConfigCaps, self).parse_dom(xmldoc)
+
+        for c in xmldoc.getchildren():
+            if c.tag == "host":
+                host = LibvirtConfigCapsHost()
+                host.parse_dom(c)
+                self.host = host
+            elif c.tag == "guest":
+                guest = LibvirtConfigCapsGuest()
+                guest.parse_dom(c)
+                self.guests.append(guest)
+
+    def format_dom(self):
+        caps = super(LibvirtConfigCaps, self).format_dom()
+
+        if self.host:
+            caps.append(self.host.format_dom())
+        for g in self.guests:
+            caps.append(g.format_dom())
+
+        return caps
+
+
+class LibvirtConfigCapsHost(LibvirtConfigObject):
+
+    def __init__(self, **kwargs):
+        super(LibvirtConfigCapsHost, self).__init__(root_name="host",
+                                                    **kwargs)
+
+        self.cpu = None
+
+    def parse_dom(self, xmldoc):
+        super(LibvirtConfigCapsHost, self).parse_dom(xmldoc)
+
+        for c in xmldoc.getchildren():
+            if c.tag == "cpu":
+                cpu = LibvirtConfigCPU()
+                cpu.parse_dom(c)
+                self.cpu = cpu
+
+    def format_dom(self):
+        caps = super(LibvirtConfigCapsHost, self).format_dom()
+
+        if self.cpu:
+            caps.append(self.cpu.format_dom())
+
+        return caps
+
+
+class LibvirtConfigCapsGuest(LibvirtConfigObject):
+
+    def __init__(self, **kwargs):
+        super(LibvirtConfigCapsGuest, self).__init__(root_name="guest",
+                                                     **kwargs)
+
+        self.arch = None
+        self.ostype = None
+
+    def parse_dom(self, xmldoc):
+        super(LibvirtConfigCapsGuest, self).parse_dom(xmldoc)
+
+        for c in xmldoc.getchildren():
+            if c.tag == "os_type":
+                self.ostype = c.text
+            elif c.tag == "arch":
+                self.arch = c.get("name")
+
+    def format_dom(self):
+        caps = super(LibvirtConfigCapsGuest, self).format_dom()
+
+        if self.ostype is not None:
+            caps.append(self._text_node("os_type", self.ostype))
+        if self.arch:
+            arch = etree.Element("arch", name=self.arch)
+            caps.append(arch)
+
+        return caps
+
+
 class LibvirtConfigGuestTimer(LibvirtConfigObject):
 
     def __init__(self, **kwargs):
@@ -132,6 +220,11 @@ def __init__(self, name=None, **kwargs):
 
         self.name = name
 
+    def parse_dom(self, xmldoc):
+        super(LibvirtConfigCPUFeature, self).parse_dom(xmldoc)
+
+        self.name = xmldoc.get("name")
+
     def format_dom(self):
         ft = super(LibvirtConfigCPUFeature, self).format_dom()
 
@@ -156,6 +249,25 @@ def __init__(self, **kwargs):
 
         self.features = []
 
+    def parse_dom(self, xmldoc):
+        super(LibvirtConfigCPU, self).parse_dom(xmldoc)
+
+        for c in xmldoc.getchildren():
+            if c.tag == "arch":
+                self.arch = c.text
+            elif c.tag == "model":
+                self.model = c.text
+            elif c.tag == "vendor":
+                self.vendor = c.text
+            elif c.tag == "topology":
+                self.sockets = int(c.get("sockets"))
+                self.cores = int(c.get("cores"))
+                self.threads = int(c.get("threads"))
+            elif c.tag == "feature":
+                f = LibvirtConfigCPUFeature()
+                f.parse_dom(c)
+                self.add_feature(f)
+
     def format_dom(self):
         cpu = super(LibvirtConfigCPU, self).format_dom()