[libvirt] [PATCH v2] virsh: use virConnectGetDomainCapabilities with maxvcpus

[Shivaprasad G Bhat]

virsh maxvcpus --type kvm output is useless on PPC. Also, in
commit e6806d79 we documented not rely on virConnectGetMaxVcpus
output. Fix the  maxvcpus to use virConnectGetDomainCapabilities
now to make it useful. The call is made to use the default emulator
binary and to check for the host machine and arch which is what the
command intends to show anyway.

Signed-off-by: Shivaprasad G Bhat <sbhat at linux.vnet.ibm.com>
---
 tools/virsh-host.c |   26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/tools/virsh-host.c b/tools/virsh-host.c
index 57f0c0e..dd6ff4e 100644
--- a/tools/virsh-host.c
+++ b/tools/virsh-host.c
@@ -606,15 +606,37 @@ static bool
 cmdMaxvcpus(vshControl *ctl, const vshCmd *cmd)
 {
     const char *type = NULL;
-    int vcpus;
+    int vcpus = -1;
+    char *caps = NULL;
+    const unsigned int flags = 0; /* No flags so far */
+    xmlDocPtr xml = NULL;
+    xmlXPathContextPtr ctxt = NULL;
     virshControlPtr priv = ctl->privData;
 
     if (vshCommandOptStringReq(ctl, cmd, "type", &type) < 0)
         return false;
 
+    caps = virConnectGetDomainCapabilities(priv->conn, NULL, NULL, NULL, type, flags);
+    if (!caps)
+        goto fallback;
+
+    xml = virXMLParseStringCtxt(caps, _("(domainCapabilities)"), &ctxt);
+    if (!xml) {
+        VIR_FREE(caps);
+        goto fallback;
+    }
+
+    virXPathInt("string(./vcpu[1]/@max)", ctxt, &vcpus);
+
+    xmlXPathFreeContext(ctxt);
+    xmlFreeDoc(xml);
+    if (vcpus > 0)
+        goto exit;
+
+ fallback:
     if ((vcpus = virConnectGetMaxVcpus(priv->conn, type)) < 0)
         return false;
-
+ exit:
     vshPrint(ctl, "%d\n", vcpus);
 
     return true;