commit bbe97ae968eba60b71e0066d49f9fc909966d9d6
Author: Jim Fehlig <jfehlig@suse.com>
Date:   Fri May 10 12:05:00 2013 -0600

    Fix starting domains when kernel has no cgroups support
    
    Found that I was unable to start existing domains after updating
    to a kernel with no cgroups support
    
      # zgrep CGROUP /proc/config.gz
      # CONFIG_CGROUPS is not set
      # virsh start test
      error: Failed to start domain test
      error: Unable to initialize /machine cgroup: Cannot allocate memory
    
    virCgroupPartitionNeedsEscaping() correctly returns errno (ENOENT) when
    attempting to open /proc/cgroups on such a system, but it was being
    dropped in virCgroupSetPartitionSuffix().
    
    Change virCgroupSetPartitionSuffix() to propagate errors returned by
    its callees.  Also check for ENOENT in qemuInitCgroup() when determining
    if cgroups support is available.

Index: libvirt-1.0.5/src/qemu/qemu_cgroup.c
===================================================================
--- libvirt-1.0.5.orig/src/qemu/qemu_cgroup.c
+++ libvirt-1.0.5/src/qemu/qemu_cgroup.c
@@ -445,7 +445,8 @@ int qemuInitCgroup(virQEMUDriverPtr driv
         if (rc != 0) {
             if (rc == -ENXIO ||
                 rc == -EPERM ||
-                rc == -EACCES) { /* No cgroups mounts == success */
+                rc == -EACCES ||
+                rc == -ENOENT) { /* No cgroups mounts == success */
                 VIR_DEBUG("No cgroups present/configured/accessible, ignoring error");
                 goto done;
             }
Index: libvirt-1.0.5/src/util/vircgroup.c
===================================================================
--- libvirt-1.0.5.orig/src/util/vircgroup.c
+++ libvirt-1.0.5/src/util/vircgroup.c
@@ -1167,14 +1167,14 @@ static int virCgroupPartitionEscape(char
     return 0;
 }
 
-static char *virCgroupSetPartitionSuffix(const char *path)
+static int virCgroupSetPartitionSuffix(const char *path, char **res)
 {
     char **tokens = virStringSplit(path, "/", 0);
     size_t i;
-    char *ret = NULL;
+    int ret = -1;
 
     if (!tokens)
-        return NULL;
+        return ret;
 
     for (i = 0 ; tokens[i] != NULL ; i++) {
         /* Whitelist the 3 top level fixed dirs
@@ -1193,20 +1193,27 @@ static char *virCgroupSetPartitionSuffix
             !strchr(tokens[i], '.')) {
             if (VIR_REALLOC_N(tokens[i],
                               strlen(tokens[i]) + strlen(".partition") + 1) < 0) {
+                ret = -ENOMEM;
                 virReportOOMError();
                 goto cleanup;
             }
             strcat(tokens[i], ".partition");
         }
 
-        if (virCgroupPartitionEscape(&(tokens[i])) < 0) {
-            virReportOOMError();
+        ret = virCgroupPartitionEscape(&(tokens[i]));
+        if (ret < 0) {
+            if (ret == -ENOMEM)
+                virReportOOMError();
             goto cleanup;
         }
     }
 
-    if (!(ret = virStringJoin((const char **)tokens, "/")))
+    if (!(*res = virStringJoin((const char **)tokens, "/"))) {
+        ret = -ENOMEM;
         goto cleanup;
+    }
+
+    ret = 0;
 
 cleanup:
     virStringFreeList(tokens);
@@ -1241,9 +1248,9 @@ int virCgroupNewPartition(const char *pa
 
     /* XXX convert all cgroups APIs to use error report
      * APIs instead of returning errno */
-    if (!(newpath = virCgroupSetPartitionSuffix(path))) {
+    rc = virCgroupSetPartitionSuffix(path, &newpath);
+    if (rc < 0) {
         virResetLastError();
-        rc = -ENOMEM;
         goto cleanup;
     }