cli: Support --cpu maximum

This mode has been introduced in libvirt 7.1.0 (March 2021) and
can be already used today with

  --cpu mode=maximum

This is however slightly inconvenient to type and is not
consistent with the special treatment that the other modes
(host-passthrough, host-model) get.

Introduce a proper special mode for it.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>

man/virt-install.rst

@@ -438,6 +438,11 @@ Some examples:
 ``--cpu host-passthrough,cache.mode=passthrough``
     Example of passing through the host cpu's cache information.
 
+``--cpu maximum``
+    Expose the most feature-rich CPU possible. Useful when running a foreign
+    architecture guest, for example a riscv64 guest on an x86_64 host. Not
+    recommended when using KVM to run a same-architecture guest.
+
 Use --cpu=? to see a list of all available sub options.
 Complete details at https://libvirt.org/formatdomain.html#cpu-model-and-topology
 

tests/data/cli/compare/virt-install-linux2020.xml

@@ -19,7 +19,7 @@
     <apic/>
     <vmport state="off"/>
   </features>
-  <cpu mode="host-passthrough"/>
+  <cpu mode="maximum"/>
   <clock offset="utc">
     <timer name="rtc" tickpolicy="catchup"/>
     <timer name="pit" tickpolicy="delay"/>
@@ -102,7 +102,7 @@
     <apic/>
     <vmport state="off"/>
   </features>
-  <cpu mode="host-passthrough"/>
+  <cpu mode="maximum"/>
   <clock offset="utc">
     <timer name="rtc" tickpolicy="catchup"/>
     <timer name="pit" tickpolicy="delay"/>

tests/test_cli.py

@@ -1153,7 +1153,7 @@ c.add_compare("--os-variant http://fedoraproject.org/fedora/20 --disk %(EXISTIMG
 c.add_compare("--cdrom %(EXISTIMG2)s --file %(EXISTIMG1)s --os-variant win2k3 --sound --controller usb", "kvm-win2k3-cdrom")  # HVM windows install with disk
 c.add_compare("--os-variant name=ubuntusaucy --nodisks --boot cdrom --virt-type qemu --cpu Penryn --input tablet --boot uefi --graphics vnc", "qemu-plain")  # plain qemu
 c.add_compare("--os-variant fedora20 --nodisks --boot network --graphics default --arch i686 --rng none", "qemu-32-on-64", prerun_check=has_old_osinfo)  # 32 on 64
-c.add_compare("--osinfo linux2020 --pxe", "linux2020", prerun_check=no_osinfo_linux2020_virtio)
+c.add_compare("--osinfo linux2020 --pxe --cpu maximum", "linux2020", prerun_check=no_osinfo_linux2020_virtio) # also --cpu maximum
 c.add_compare("--check disk_size=off --osinfo win11 --cdrom %(EXISTIMG1)s", "win11", prerun_check=no_osinfo_win11)
 c.add_compare("--check disk_size=off --osinfo win11 --cdrom %(EXISTIMG1)s --boot uefi=off", "win11-no-uefi")
 c.add_compare("--osinfo generic --disk none --location %(ISO-NO-OS)s,kernel=frib.img,initrd=/frob.img", "location-manual-kernel", prerun_check=missing_xorriso)  # --location with an unknown ISO but manually specified kernel paths

virtinst/domain/cpu.py

@@ -267,12 +267,13 @@ class DomainCpu(XMLBuilder):
     SPECIAL_MODE_HOST_COPY = "host-copy"
     SPECIAL_MODE_HOST_MODEL = "host-model"
     SPECIAL_MODE_HOST_PASSTHROUGH = "host-passthrough"
+    SPECIAL_MODE_MAXIMUM = "maximum"
     SPECIAL_MODE_CLEAR = "clear"
     SPECIAL_MODE_APP_DEFAULT = "default"
     SPECIAL_MODES = [SPECIAL_MODE_HOST_MODEL_ONLY, SPECIAL_MODE_HV_DEFAULT,
                      SPECIAL_MODE_HOST_COPY, SPECIAL_MODE_HOST_MODEL,
-                     SPECIAL_MODE_HOST_PASSTHROUGH, SPECIAL_MODE_CLEAR,
+                     SPECIAL_MODE_HOST_PASSTHROUGH, SPECIAL_MODE_MAXIMUM,
-                     SPECIAL_MODE_APP_DEFAULT]
+                     SPECIAL_MODE_CLEAR, SPECIAL_MODE_APP_DEFAULT]
 
     def _get_app_default_mode(self, guest):
         # Depending on if libvirt+qemu is new enough, we prefer
@@ -295,7 +296,8 @@ class DomainCpu(XMLBuilder):
             log.debug("Using default cpu mode=%s", val)
 
         if (val == self.SPECIAL_MODE_HOST_MODEL or
-            val == self.SPECIAL_MODE_HOST_PASSTHROUGH):
+            val == self.SPECIAL_MODE_HOST_PASSTHROUGH or
+            val == self.SPECIAL_MODE_MAXIMUM):
             self.model = None
             self.vendor = None
             self.model_fallback = None