[libvirt] [PATCH] Host cpu offline/online removes the cpus available for vms

[Shivaprasad G Bhat]

Online/Offline operations on the host cpus removes the machine/cpuset.cpus
which are never added back. The guests with vcpu pinning can fail to boot
unless the xml is edited.

If the possibility that the offlined cpus are onlined back, the cpuset.cpus can be updated upon start of the guest thus allowing the guests to boot back without
erroring out.

Signed-off-by: Shivaprasad G Bhat <sbhat at linux.vnet.ibm.com>
---
 src/util/vircgroup.c |   27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
index a6d60c5..52575c9 100644
--- a/src/util/vircgroup.c
+++ b/src/util/vircgroup.c
@@ -72,6 +72,7 @@ typedef enum {
                                        * before creating subcgroups and
                                        * attaching tasks
                                        */
+    VIR_CGROUP_CPUS_HIERACHY = 1 << 1, /* call virCgroupCpuSetInherit */
 } virCgroupFlags;
 
 
@@ -891,6 +892,7 @@ virCgroupMakeGroup(virCgroupPtr parent,
     VIR_DEBUG("Make group %s", group->path);
     for (i = 0; i < VIR_CGROUP_CONTROLLER_LAST; i++) {
         char *path = NULL;
+        int inheritCpuset = 0;
 
         /* We must never mkdir() in systemd's hierarchy */
         if (i == VIR_CGROUP_CONTROLLER_SYSTEMD) {
@@ -933,15 +935,7 @@ virCgroupMakeGroup(virCgroupPtr parent,
                     goto cleanup;
                 }
             }
-            if (group->controllers[VIR_CGROUP_CONTROLLER_CPUSET].mountPoint != NULL &&
-                (i == VIR_CGROUP_CONTROLLER_CPUSET ||
-                 STREQ(group->controllers[i].mountPoint,
-                       group->controllers[VIR_CGROUP_CONTROLLER_CPUSET].mountPoint))) {
-                if (virCgroupCpuSetInherit(parent, group) < 0) {
-                    VIR_FREE(path);
-                    goto cleanup;
-                }
-            }
+            inheritCpuset = 1;
             /*
              * Note that virCgroupSetMemoryUseHierarchy should always be
              * called prior to creating subcgroups and attaching tasks.
@@ -958,6 +952,19 @@ virCgroupMakeGroup(virCgroupPtr parent,
             }
         }
 
+        if (inheritCpuset || (flags & VIR_CGROUP_CPUS_HIERACHY))
+        {
+            if (group->controllers[VIR_CGROUP_CONTROLLER_CPUSET].mountPoint != NULL &&
+                (i == VIR_CGROUP_CONTROLLER_CPUSET ||
+                 STREQ(group->controllers[i].mountPoint,
+                       group->controllers[VIR_CGROUP_CONTROLLER_CPUSET].mountPoint))) {
+                if (virCgroupCpuSetInherit(parent, group) < 0) {
+                    VIR_FREE(path);
+                    goto cleanup;
+                }
+            }
+        }
+
         VIR_FREE(path);
     }
 
@@ -1275,7 +1282,7 @@ virCgroupNewPartition(const char *path,
         if (virCgroupNew(-1, parentPath, NULL, controllers, &parent) < 0)
             goto cleanup;
 
-        if (virCgroupMakeGroup(parent, *group, create, VIR_CGROUP_NONE) < 0) {
+        if (virCgroupMakeGroup(parent, *group, create, VIR_CGROUP_CPUS_HIERACHY) < 0) {
             virCgroupRemove(*group);
             goto cleanup;
         }