python: Use virNodeGetCPUMap where possible

Modified the places where virNodeGetInfo was used for the purpose
of obtaining the maximum node CPU number. Transparently falling
back to virNodeGetInfo in case of failure.
Wrote a utility function getPyNodeCPUCount for that purpose.
Signed-off-by: NViktor Mihajlovski <mihajlov@linux.vnet.ibm.com>

python/libvirt-override.c

@@ -253,6 +253,39 @@ cleanup:
     return NULL;
 }
 
+/*
+ * Utility function to retrieve the number of node CPUs present.
+ * It first tries virGetNodeCPUMap, which will return the
+ * number reliably, if available.
+ * As a fallback and for compatibility with backlevel libvirt
+ * versions virGetNodeInfo will be called to calculate the
+ * CPU number, which has the potential to return a too small
+ * number if some host CPUs are offline.
+ */
+static int
+getPyNodeCPUCount(virConnectPtr conn) {
+    int i_retval;
+    virNodeInfo nodeinfo;
+
+    LIBVIRT_BEGIN_ALLOW_THREADS;
+    i_retval = virNodeGetCPUMap(conn, NULL, NULL, 0);
+    LIBVIRT_END_ALLOW_THREADS;
+
+    if (i_retval < 0) {
+        /* fallback: use nodeinfo */
+        LIBVIRT_BEGIN_ALLOW_THREADS;
+        i_retval = virNodeGetInfo(conn, &nodeinfo);
+        LIBVIRT_END_ALLOW_THREADS;
+        if (i_retval < 0)
+            goto cleanup;
+
+        i_retval = VIR_NODEINFO_MAXCPUS(nodeinfo);
+    }
+
+cleanup:
+    return i_retval;
+}
+
 /************************************************************************
  *									*
  *		Statistics						*
@@ -1338,22 +1371,18 @@ libvirt_virDomainGetVcpus(PyObject *self ATTRIBUTE_UNUSED,
     virDomainPtr domain;
     PyObject *pyobj_domain, *pyretval = NULL, *pycpuinfo = NULL, *pycpumap = NULL;
     PyObject *error = NULL;
-    virNodeInfo nodeinfo;
     virDomainInfo dominfo;
     virVcpuInfoPtr cpuinfo = NULL;
     unsigned char *cpumap = NULL;
     size_t cpumaplen, i;
-    int i_retval;
+    int i_retval, cpunum;
 
     if (!PyArg_ParseTuple(args, (char *)"O:virDomainGetVcpus",
                           &pyobj_domain))
         return NULL;
     domain = (virDomainPtr) PyvirDomain_Get(pyobj_domain);
 
-    LIBVIRT_BEGIN_ALLOW_THREADS;
-    i_retval = virNodeGetInfo(virDomainGetConnect(domain), &nodeinfo);
-    LIBVIRT_END_ALLOW_THREADS;
-    if (i_retval < 0)
+    if ((cpunum = getPyNodeCPUCount(virDomainGetConnect(domain))) < 0)
         return VIR_PY_INT_FAIL;
 
     LIBVIRT_BEGIN_ALLOW_THREADS;
@@ -1365,7 +1394,7 @@ libvirt_virDomainGetVcpus(PyObject *self ATTRIBUTE_UNUSED,
     if (VIR_ALLOC_N(cpuinfo, dominfo.nrVirtCpu) < 0)
         return PyErr_NoMemory();
 
-    cpumaplen = VIR_CPU_MAPLEN(VIR_NODEINFO_MAXCPUS(nodeinfo));
+    cpumaplen = VIR_CPU_MAPLEN(cpunum);
     if (xalloc_oversized(dominfo.nrVirtCpu, cpumaplen) ||
         VIR_ALLOC_N(cpumap, dominfo.nrVirtCpu * cpumaplen) < 0) {
         error = PyErr_NoMemory();
@@ -1423,11 +1452,11 @@ libvirt_virDomainGetVcpus(PyObject *self ATTRIBUTE_UNUSED,
             goto cleanup;
     }
     for (i = 0 ; i < dominfo.nrVirtCpu ; i++) {
-        PyObject *info = PyTuple_New(VIR_NODEINFO_MAXCPUS(nodeinfo));
+        PyObject *info = PyTuple_New(cpunum);
         int j;
         if (info == NULL)
             goto cleanup;
-        for (j = 0 ; j < VIR_NODEINFO_MAXCPUS(nodeinfo) ; j++) {
+        for (j = 0 ; j < cpunum ; j++) {
             PyObject *item = NULL;
             if ((item = PyBool_FromLong(VIR_CPU_USABLE(cpumap, cpumaplen, i, j))) == NULL ||
                 PyTuple_SetItem(info, j, item) < 0) {
@@ -1467,9 +1496,8 @@ libvirt_virDomainPinVcpu(PyObject *self ATTRIBUTE_UNUSED,
     virDomainPtr domain;
     PyObject *pyobj_domain, *pycpumap;
     PyObject *ret = NULL;
-    virNodeInfo nodeinfo;
     unsigned char *cpumap;
-    int cpumaplen, i, vcpu, tuple_size;
+    int cpumaplen, i, vcpu, tuple_size, cpunum;
     int i_retval;
 
     if (!PyArg_ParseTuple(args, (char *)"OiO:virDomainPinVcpu",
@@ -1477,10 +1505,7 @@ libvirt_virDomainPinVcpu(PyObject *self ATTRIBUTE_UNUSED,
         return NULL;
     domain = (virDomainPtr) PyvirDomain_Get(pyobj_domain);
 
-    LIBVIRT_BEGIN_ALLOW_THREADS;
-    i_retval = virNodeGetInfo(virDomainGetConnect(domain), &nodeinfo);
-    LIBVIRT_END_ALLOW_THREADS;
-    if (i_retval < 0)
+    if ((cpunum = getPyNodeCPUCount(virDomainGetConnect(domain))) < 0)
         return VIR_PY_INT_FAIL;
 
     if (PyTuple_Check(pycpumap)) {
@@ -1492,7 +1517,7 @@ libvirt_virDomainPinVcpu(PyObject *self ATTRIBUTE_UNUSED,
        return ret;
     }
 
-    cpumaplen = VIR_CPU_MAPLEN(VIR_NODEINFO_MAXCPUS(nodeinfo));
+    cpumaplen = VIR_CPU_MAPLEN(cpunum);
     if (VIR_ALLOC_N(cpumap, cpumaplen) < 0)
         return PyErr_NoMemory();
 
@@ -1509,7 +1534,7 @@ libvirt_virDomainPinVcpu(PyObject *self ATTRIBUTE_UNUSED,
             VIR_UNUSE_CPU(cpumap, i);
     }
 
-    for (; i < VIR_NODEINFO_MAXCPUS(nodeinfo); i++)
+    for (; i < cpunum; i++)
         VIR_UNUSE_CPU(cpumap, i);
 
     LIBVIRT_BEGIN_ALLOW_THREADS;
@@ -1534,9 +1559,8 @@ libvirt_virDomainPinVcpuFlags(PyObject *self ATTRIBUTE_UNUSED,
     virDomainPtr domain;
     PyObject *pyobj_domain, *pycpumap;
     PyObject *ret = NULL;
-    virNodeInfo nodeinfo;
     unsigned char *cpumap;
-    int cpumaplen, i, vcpu, tuple_size;
+    int cpumaplen, i, vcpu, tuple_size, cpunum;
     unsigned int flags;
     int i_retval;
 
@@ -1545,10 +1569,7 @@ libvirt_virDomainPinVcpuFlags(PyObject *self ATTRIBUTE_UNUSED,
         return NULL;
     domain = (virDomainPtr) PyvirDomain_Get(pyobj_domain);
 
-    LIBVIRT_BEGIN_ALLOW_THREADS;
-    i_retval = virNodeGetInfo(virDomainGetConnect(domain), &nodeinfo);
-    LIBVIRT_END_ALLOW_THREADS;
-    if (i_retval < 0)
+    if ((cpunum = getPyNodeCPUCount(virDomainGetConnect(domain))) < 0)
         return VIR_PY_INT_FAIL;
 
     if (PyTuple_Check(pycpumap)) {
@@ -1560,7 +1581,7 @@ libvirt_virDomainPinVcpuFlags(PyObject *self ATTRIBUTE_UNUSED,
        return ret;
     }
 
-    cpumaplen = VIR_CPU_MAPLEN(VIR_NODEINFO_MAXCPUS(nodeinfo));
+    cpumaplen = VIR_CPU_MAPLEN(cpunum);
     if (VIR_ALLOC_N(cpumap, cpumaplen) < 0)
         return PyErr_NoMemory();
 
@@ -1577,7 +1598,7 @@ libvirt_virDomainPinVcpuFlags(PyObject *self ATTRIBUTE_UNUSED,
             VIR_UNUSE_CPU(cpumap, i);
     }
 
-    for (; i < VIR_NODEINFO_MAXCPUS(nodeinfo); i++)
+    for (; i < cpunum; i++)
         VIR_UNUSE_CPU(cpumap, i);
 
     LIBVIRT_BEGIN_ALLOW_THREADS;
@@ -1599,23 +1620,19 @@ libvirt_virDomainGetVcpuPinInfo(PyObject *self ATTRIBUTE_UNUSED,
                                 PyObject *args) {
     virDomainPtr domain;
     PyObject *pyobj_domain, *pycpumaps = NULL;
-    virNodeInfo nodeinfo;
     virDomainInfo dominfo;
     unsigned char *cpumaps;
     size_t cpumaplen, vcpu, pcpu;
     unsigned int flags;
-    int i_retval;
+    int i_retval, cpunum;
 
     if (!PyArg_ParseTuple(args, (char *)"Oi:virDomainGetVcpuPinInfo",
                           &pyobj_domain, &flags))
         return NULL;
     domain = (virDomainPtr) PyvirDomain_Get(pyobj_domain);
 
-    LIBVIRT_BEGIN_ALLOW_THREADS;
-    i_retval = virNodeGetInfo(virDomainGetConnect(domain), &nodeinfo);
-    LIBVIRT_END_ALLOW_THREADS;
-    if (i_retval < 0)
-        return VIR_PY_NONE;
+    if ((cpunum = getPyNodeCPUCount(virDomainGetConnect(domain))) < 0)
+        return VIR_PY_INT_FAIL;
 
     LIBVIRT_BEGIN_ALLOW_THREADS;
     i_retval = virDomainGetInfo(domain, &dominfo);
@@ -1623,7 +1640,7 @@ libvirt_virDomainGetVcpuPinInfo(PyObject *self ATTRIBUTE_UNUSED,
     if (i_retval < 0)
         return VIR_PY_NONE;
 
-    cpumaplen = VIR_CPU_MAPLEN(VIR_NODEINFO_MAXCPUS(nodeinfo));
+    cpumaplen = VIR_CPU_MAPLEN(cpunum);
     if (xalloc_oversized(dominfo.nrVirtCpu, cpumaplen) ||
         VIR_ALLOC_N(cpumaps, dominfo.nrVirtCpu * cpumaplen) < 0)
         goto cleanup;
@@ -1639,11 +1656,11 @@ libvirt_virDomainGetVcpuPinInfo(PyObject *self ATTRIBUTE_UNUSED,
         goto cleanup;
 
     for (vcpu = 0; vcpu < dominfo.nrVirtCpu; vcpu++) {
-        PyObject *mapinfo = PyTuple_New(VIR_NODEINFO_MAXCPUS(nodeinfo));
+        PyObject *mapinfo = PyTuple_New(cpunum);
         if (mapinfo == NULL)
             goto cleanup;
 
-        for (pcpu = 0; pcpu < VIR_NODEINFO_MAXCPUS(nodeinfo); pcpu++) {
+        for (pcpu = 0; pcpu < cpunum; pcpu++) {
             PyTuple_SetItem(mapinfo, pcpu,
                             PyBool_FromLong(VIR_CPU_USABLE(cpumaps, cpumaplen, vcpu, pcpu)));
         }