virtinst: compare host and domain cpu models

Lookup the domain capabilities CPU model and compare with
the host capabilities CPU model and if they are not equal
set the guest's CPU model to None.

(crobinso: compare against 'custom' list not 'host-model', move
 to separate function)

2 files changed, 29 insertions, 7 deletions

diff --git a/tests/cli-test-xml/compare/virt-install-boot-uefi.xml b/tests/cli-test-xml/compare/virt-install-boot-uefi.xml
index 7216ec68..498d4295 100644
--- a/tests/cli-test-xml/compare/virt-install-boot-uefi.xml
+++ b/tests/cli-test-xml/compare/virt-install-boot-uefi.xml
@@ -15,9 +15,7 @@
     <smm state="on"/>
     <vmport state="off"/>
   </features>
-  <cpu mode="custom" match="exact">
-    <model>Opteron_G4</model>
-  </cpu>
+  <cpu mode="custom" match="exact"/>
   <clock offset="utc">
     <timer name="rtc" tickpolicy="catchup"/>
     <timer name="pit" tickpolicy="delay"/>
diff --git a/virtinst/guest.py b/virtinst/guest.py
index 5e7d8077..563203b4 100644
--- a/virtinst/guest.py
+++ b/virtinst/guest.py
@@ -847,6 +847,33 @@ class Guest(XMLBuilder):
             else:
                 self.emulator = "/usr/lib/xen/bin/qemu-dm"
 
+    def _set_cpu_x86_kvm_default(self):
+        if self.os.arch != self.conn.caps.host.cpu.arch:
+            return
+
+        self.cpu.set_special_mode(self.x86_cpu_default)
+        if self.x86_cpu_default != self.cpu.SPECIAL_MODE_HOST_MODEL_ONLY:
+            return
+        if not self.cpu.model:
+            return
+
+        # 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(self)
+        domcaps_mode = domcaps.cpu.get_mode("custom")
+        if not domcaps_mode:
+            return
+
+        cpu_model = domcaps_mode.get_model(self.cpu.model)
+        if cpu_model and cpu_model.usable:
+            return
+
+        logging.debug("Host capabilities CPU '%s' is not supported "
+            "according to domain capabilities. Unsettings CPU model",
+            self.cpu.model)
+        self.cpu.model = None
+
     def _set_cpu_defaults(self):
         self.cpu.set_topology_defaults(self.vcpus)
 
@@ -865,14 +892,11 @@ class Guest(XMLBuilder):
             self.cpu.model = "cortex-a57"
 
         elif self.os.is_x86() and self.type == "kvm":
-            if self.os.arch != self.conn.caps.host.cpu.arch:
-                return
+            self._set_cpu_x86_kvm_default()
 
-            self.cpu.set_special_mode(self.x86_cpu_default)
             if self._os_object.broken_x2apic():
                 self.cpu.add_feature("x2apic", policy="disable")
 
-
     def _hyperv_supported(self):
         if (self.os.loader_type == "pflash" and
             self.os_variant in ("win2k8r2", "win7")):