vshExtractCPUDefXML: Accept domain capabilities XML

The domain capabilities XML contains host CPU model tailored to a
specific hypervisor and since it's enclosed in <mode name='host-model'>
element rather then the required <cpu> it's impossible to directly use
the host CPU model as an input to, e.g., cpu-compare command. To make
this more convenient, vshExtractCPUDefXML now accepts full domain
capabilities XML and automatically transforms the host CPU models into
the form accepted by libvirt APIs.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>
Reviewed-by: NCollin Walling <walling@linux.ibm.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

tools/virsh-host.c

@@ -1114,8 +1114,9 @@ cmdURI(vshControl *ctl, const vshCmd *cmd ATTRIBUTE_UNUSED)
 
 /* Extracts the CPU definition XML strings from a file which may contain either
  *  - just the CPU definitions,
- *  - domain XMLs, or
- *  - capabilities XMLs.
+ *  - domain XMLs,
+ *  - capabilities XMLs, or
+ *  - domain capabilities XMLs.
  *
  * Returns NULL terminated string list.
  */
@@ -1143,20 +1144,37 @@ vshExtractCPUDefXMLs(vshControl *ctl,
 
     n = virXPathNodeSet("/container/cpu|"
                         "/container/domain/cpu|"
-                        "/container/capabilities/host/cpu",
+                        "/container/capabilities/host/cpu|"
+                        "/container/domainCapabilities/cpu/"
+                            "mode[@name='host-model' and @supported='yes']",
                         ctxt, &nodes);
     if (n < 0)
         goto error;
 
     if (n == 0) {
         vshError(ctl, _("File '%s' does not contain any <cpu> element or "
-                        "valid domain or capabilities XML"), xmlFile);
+                        "valid domain XML, host capabilities XML, or "
+                        "domain capabilities XML"), xmlFile);
         goto error;
     }
 
     cpus = vshCalloc(ctl, n + 1, sizeof(const char *));
 
     for (i = 0; i < n; i++) {
+        /* If the user provided domain capabilities XML, we need to replace
+         * <mode ...> element with <cpu>. */
+        if (xmlStrEqual(nodes[i]->name, BAD_CAST "mode")) {
+            xmlNodeSetName(nodes[i], (const xmlChar *)"cpu");
+            while (nodes[i]->properties) {
+                if (xmlRemoveProp(nodes[i]->properties) < 0) {
+                    vshError(ctl,
+                             _("Cannot extract CPU definition from domain "
+                               "capabilities XML"));
+                    goto error;
+                }
+            }
+        }
+
         if (!(cpus[i] = virXMLNodeToString(xml, nodes[i]))) {
             vshSaveLibvirtError();
             goto error;

tools/virsh.pod

@@ -589,9 +589,11 @@ Compare CPU definition from XML <file> with host CPU. The XML <file> may
 contain either host or guest CPU definition. The host CPU definition is the
 <cpu> element and its contents as printed by B<capabilities> command. The
 guest CPU definition is the <cpu> element and its contents from domain XML
-definition. In addition to the <cpu> element itself, this command accepts
-full domain or capabilities XML containing the <cpu> element. For more
-information on guest CPU definition see:
+definition or the CPU definition created from the host CPU model found in
+domain capabilities XML (printed by B<domcapabilities> command). In
+addition to the <cpu> element itself, this command accepts
+full domain XML, capabilities XML, or domain capabilities XML containing
+the CPU definition. For more information on guest CPU definition see:
 L<https://libvirt.org/formatdomain.html#elementsCPU>. If I<--error> is
 specified, the command will return an error when the given CPU is
 incompatible with host CPU and a message providing more details about the