libxl: implement virDomainGetMaxVcpus

The libxl driver already supports getting maximum vcpu count via
libxlDomainGetVcpusFlags, allowing to trivially implement
virDomainGetMaxVcpus.

docs/news.html.in

@@ -39,6 +39,8 @@
           _virStorageVolInfo structure. The --physical flag has been
           added to the virsh vol-info command to access the data
           </li>
+          <li>libxl: Implement virDomainGetMaxVcpus API
+          </li>
         </ul>
       </li>
       <li><strong>Improvements</strong>

src/libxl/libxl_driver.c

@@ -2362,6 +2362,13 @@ libxlDomainGetVcpusFlags(virDomainPtr dom, unsigned int flags)
     return ret;
 }
 
+static int
+libxlDomainGetMaxVcpus(virDomainPtr dom)
+{
+    return libxlDomainGetVcpusFlags(dom, (VIR_DOMAIN_AFFECT_LIVE |
+                                          VIR_DOMAIN_VCPU_MAXIMUM));
+}
+
 static int
 libxlDomainPinVcpuFlags(virDomainPtr dom, unsigned int vcpu,
                         unsigned char *cpumap, int maplen,
@@ -6446,6 +6453,7 @@ static virHypervisorDriver libxlHypervisorDriver = {
     .domainSetVcpus = libxlDomainSetVcpus, /* 0.9.0 */
     .domainSetVcpusFlags = libxlDomainSetVcpusFlags, /* 0.9.0 */
     .domainGetVcpusFlags = libxlDomainGetVcpusFlags, /* 0.9.0 */
+    .domainGetMaxVcpus = libxlDomainGetMaxVcpus, /* 3.0.0 */
     .domainPinVcpu = libxlDomainPinVcpu, /* 0.9.0 */
     .domainPinVcpuFlags = libxlDomainPinVcpuFlags, /* 1.2.1 */
     .domainGetVcpus = libxlDomainGetVcpus, /* 0.9.0 */