guest: Add DomainCapabilities caching

tests/capabilities.py

@@ -106,6 +106,11 @@ class TestCapabilities(unittest.TestCase):
         xml = open("tests/capabilities-xml/kvm-x86_64-domcaps.xml").read()
         caps = DomainCapabilities(utils.URIs.open_testdriver_cached(), xml)
 
+        self.assertEqual(caps.machine, "pc-i440fx-2.1")
+        self.assertEqual(caps.arch, "x86_64")
+        self.assertEqual(caps.domain, "kvm")
+        self.assertEqual(caps.path, "/bin/qemu-system-x86_64")
+
         custom_mode = caps.cpu.get_mode("custom")
         self.assertTrue(bool(custom_mode))
         cpu_model = custom_mode.get_model("Opteron_G4")

virtinst/domain/cpu.py

@@ -7,7 +7,6 @@
 
 import logging
 
-from ..domcapabilities import DomainCapabilities
 from ..xmlbuilder import XMLBuilder, XMLProperty, XMLChildProperty
 
 
@@ -206,20 +205,14 @@ class DomainCpu(XMLBuilder):
     # Default config #
     ##################
 
-    def _set_cpu_x86_kvm_default(self, guest):
-        if guest.os.arch != self.conn.caps.host.cpu.arch:
-            return
-
-        self.set_special_mode(guest.x86_cpu_default)
-        if guest.x86_cpu_default != self.SPECIAL_MODE_HOST_MODEL_ONLY:
-            return
-        if not self.model:
-            return
-
+    def _validate_default_host_model_only(self, guest):
         # It's possible that the value HOST_MODEL_ONLY gets from
         # <capabilities> is not actually supported by qemu/kvm
         # combo which will be reported in <domainCapabilities>
-        domcaps = DomainCapabilities.build_from_guest(guest)
+        if not self.model:
+            return
+
+        domcaps = guest.lookup_domcaps()
         domcaps_mode = domcaps.cpu.get_mode("custom")
         if not domcaps_mode:
             return
@@ -233,6 +226,15 @@ class DomainCpu(XMLBuilder):
             self.model)
         self.model = None
 
+    def _set_cpu_x86_kvm_default(self, guest):
+        if guest.os.arch != self.conn.caps.host.cpu.arch:
+            return
+
+        mode = guest.x86_cpu_default
+        self.set_special_mode(mode)
+        if mode == self.SPECIAL_MODE_HOST_MODEL_ONLY:
+            self._validate_default_host_model_only(guest)
+
     def set_defaults(self, guest):
         self.set_topology_defaults(guest.vcpus)
 

virtinst/domcapabilities.py

@@ -217,6 +217,9 @@ class DomainCapabilities(XMLBuilder):
     os = XMLChildProperty(_OS, is_single=True)
     cpu = XMLChildProperty(_CPU, is_single=True)
     devices = XMLChildProperty(_Devices, is_single=True)
+    features = XMLChildProperty(_Features, is_single=True)
 
     arch = XMLProperty("./arch")
-    features = XMLChildProperty(_Features, is_single=True)
+    domain = XMLProperty("./domain")
+    machine = XMLProperty("./machine")
+    path = XMLProperty("./path")

virtinst/guest.py

@@ -165,6 +165,7 @@ class Guest(XMLBuilder):
 
         self.__osinfo = None
         self._capsinfo = None
+        self._domcaps = None
 
 
     ######################
@@ -326,7 +327,7 @@ class Guest(XMLBuilder):
         """
         if not self.os.arch:
             self.set_capabilities_defaults()
-        domcaps = DomainCapabilities.build_from_guest(self)
+        domcaps = self.lookup_domcaps()
 
         if not domcaps.supports_uefi_xml():
             raise RuntimeError(_("Libvirt version does not support UEFI."))
@@ -408,10 +409,26 @@ class Guest(XMLBuilder):
             return False
         return True
 
-    def lookup_capsinfo(self):
-        def _compare_to_capsinfo(capsinfo):
-            if not capsinfo:
+    def lookup_domcaps(self):
+        # We need to regenerate domcaps cache if any of these values change
+        def _compare(domcaps):
+            if self.os.machine and self.os.machine != domcaps.machine:
                 return False
+            if self.type and self.type != domcaps.domain:
+                return False
+            if self.os.arch and self.os.arch != domcaps.arch:
+                return False
+            if self.emulator and self.emulator != domcaps.path:
+                return False
+            return True
+
+        if not self._domcaps or not _compare(self._domcaps):
+            self._domcaps = DomainCapabilities.build_from_guest(self)
+        return self._domcaps
+
+    def lookup_capsinfo(self):
+        # We need to regenerate capsinfo cache if any of these values change
+        def _compare(capsinfo):
             if self.type and self.type != capsinfo.hypervisor_type:
                 return False
             if self.os.os_type and self.os.os_type != capsinfo.os_type:
@@ -422,7 +439,7 @@ class Guest(XMLBuilder):
                 return False
             return True
 
-        if not _compare_to_capsinfo(self._capsinfo):
+        if not self._capsinfo or not _compare(self._capsinfo):
             self._capsinfo = self.conn.caps.guest_lookup(
                 os_type=self.os.os_type,
                 arch=self.os.arch,