devices: tpm: Rework defaults

The code previously was just encoding the same defaults as libvirt,
which doesn't really add anything.

Instead, let's prefer type='emulator' model='tpm-crb', which
gives the most modern virtualization friendly config. When we don't
know if that will work, we mostly leave things up to libvirt to fill
in.

Signed-off-by: Cole Robinson <crobinso@redhat.com>

3 files changed, 37 insertions, 5 deletions

diff --git a/virtinst/cli.py b/virtinst/cli.py
index c0a4391a..a5d9dc08 100644
--- a/virtinst/cli.py
+++ b/virtinst/cli.py
@@ -4107,8 +4107,14 @@ class ParserTPM(VirtCLIParser):
             self.guest.skip_default_tpm = True
             return
 
+        # Handle --tpm /dev/tpm0
         if (self.optdict.get("type", "").startswith("/")):
             self.optdict["path"] = self.optdict.pop("type")
+
+        # Let --tpm default,... hit our DeviceTpm defaults code
+        if self.optdict.get("type") == "default":
+            self.optdict.pop("type")
+
         return super()._parse(inst)
 
     @classmethod
diff --git a/virtinst/devices/tpm.py b/virtinst/devices/tpm.py
index bcc19482..aca3e0f2 100644
--- a/virtinst/devices/tpm.py
+++ b/virtinst/devices/tpm.py
@@ -49,11 +49,32 @@ class DeviceTpm(Device):
     # Default config #
     ##################
 
+    @staticmethod
+    def default_model(guest):
+        domcaps = guest.lookup_domcaps()
+
+        if not domcaps.devices.tpm.present and not guest.os.is_pseries():
+            # Preserve the old default when domcaps is old
+            return DeviceTpm.MODEL_CRB
+        if domcaps.devices.tpm.get_enum("model").has_value(DeviceTpm.MODEL_CRB):
+            # CRB is the modern version, and it implies version 2.0
+            return DeviceTpm.MODEL_CRB
+
+        # Let libvirt decide so we don't need to duplicate its arch logic
+        return None
+
     def set_defaults(self, guest):
-        if not self.type:
+        if self.device_path and not self.type:
             self.type = self.TYPE_PASSTHROUGH
-        if not self.model:
-            self.model = self.MODEL_TIS
+        if not self.type:
+            # Libvirt requires a backend type to be specified. 'emulator'
+            # may not be available if swtpm is not installed, but trying to
+            # fallback to 'passthrough' in that case isn't really workable.
+            # Instead we specify it unconditionally and let libvirt error.
+            self.type = self.TYPE_EMULATOR
 
-            if guest.os.is_ppc64():
-                self.model = self.MODEL_SPAPR
+        # passthrough and model and version are all interconnected, so
+        # don't try to set a default model if other bits are set
+        if (self.type == self.TYPE_EMULATOR and
+            not self.model and not self.version):
+            self.model = self.default_model(guest)
diff --git a/virtinst/domcapabilities.py b/virtinst/domcapabilities.py
index 1153c980..431e7dc7 100644
--- a/virtinst/domcapabilities.py
+++ b/virtinst/domcapabilities.py
@@ -42,8 +42,13 @@ class _Enum(_HasValues):
 
 class _CapsBlock(_HasValues):
     supported = XMLProperty("./@supported", is_yesno=True)
+    _supported_present = XMLProperty("./@supported")
     enums = XMLChildProperty(_Enum)
 
+    @property
+    def present(self):
+        return self._supported_present is not None
+
     def enum_names(self):
         return [e.name for e in self.enums]