capabilities: Advertise cpuselection if -cpu host is usable

When -cpu host is supported by a QEMU binary, a user can use
<cpu mode='host-passthrough'/> in domain XML even when libvirtd failed
to find a matching model for the host CPU. Let's make it obvious by
advertising <cpuselection/> guest capability whenever -cpu host is
supported.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

src/qemu/qemu_capabilities.c

@@ -928,9 +928,10 @@ virQEMUCapsInitGuestFromBinary(virCapsPtr caps,
     machines = NULL;
     nmachines = 0;
 
-    if (caps->host.cpu &&
-        caps->host.cpu->model &&
-        virQEMUCapsGetCPUDefinitions(qemubinCaps, NULL) > 0 &&
+    if ((virQEMUCapsGet(qemubinCaps, QEMU_CAPS_CPU_HOST) ||
+         (caps->host.cpu &&
+          caps->host.cpu->model &&
+          virQEMUCapsGetCPUDefinitions(qemubinCaps, NULL) > 0)) &&
         !virCapabilitiesAddGuestFeature(guest, "cpuselection", true, false))
         goto cleanup;
 

tests/qemucaps2xmldata/all_1.6.0-1.xml

@@ -18,6 +18,7 @@
       </domain>
     </arch>
     <features>
+      <cpuselection/>
       <deviceboot/>
       <disksnapshot default='on' toggle='no'/>
       <acpi default='on' toggle='yes'/>

tests/qemucaps2xmldata/nodisksnapshot_1.6.0-1.xml

@@ -18,6 +18,7 @@
       </domain>
     </arch>
     <features>
+      <cpuselection/>
       <deviceboot/>
       <disksnapshot default='off' toggle='no'/>
       <acpi default='on' toggle='yes'/>