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[libvirt] [PATCH v2 1/4] Add helpers to support cpu hotplug in libvirt.



This patch adds some helpers to support cpu hotplug in libvirt.

virHotplugGetCpuidFromMsg():
    Get cpuid from cpu hotplug netlink message. The message is of the following
    format:
    {online|offline}@/devices/system/cpu/cpuxx (xx is cpuid)

virHotplugUpdateCgroupCpuset():
    Update the cpuset.cpus in the specified cgroup when a cpu is hotpluged.

virHotplugSetCpusetToLastest():
    Copy the cpuset from root to the specified cgroup.
    This function could be used when there are cpu houplug events occurred
    when libvirtd is not running.

Signed-off-by: Tang Chen <tangchen cn fujitsu com>
---
 include/libvirt/virterror.h |    2 +
 src/Makefile.am             |    1 +
 src/libvirt_private.syms    |    6 ++
 src/util/cgroup.c           |    4 +-
 src/util/cgroup.h           |    3 +
 src/util/hotplug.c          |  240 +++++++++++++++++++++++++++++++++++++++++++
 src/util/hotplug.h          |   44 ++++++++
 src/util/virterror.c        |    3 +-
 8 files changed, 300 insertions(+), 3 deletions(-)
 create mode 100644 src/util/hotplug.c
 create mode 100644 src/util/hotplug.h

diff --git a/include/libvirt/virterror.h b/include/libvirt/virterror.h
index 5140c38..aabda04 100644
--- a/include/libvirt/virterror.h
+++ b/include/libvirt/virterror.h
@@ -114,6 +114,8 @@ typedef enum {
 
     VIR_FROM_SSH = 50,       /* Error from libssh2 connection transport */
 
+    VIR_FROM_HOTPLUG = 51,      /* Error from Hotplug driver */
+
 # ifdef VIR_ENUM_SENTINELS
     VIR_ERR_DOMAIN_LAST
 # endif
diff --git a/src/Makefile.am b/src/Makefile.am
index 95e1bea..c65ee37 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -60,6 +60,7 @@ UTIL_SOURCES =							\
 		util/event.c util/event.h			\
 		util/event_poll.c util/event_poll.h		\
 		util/hooks.c util/hooks.h			\
+		util/hotplug.c util/hotplug.h			\
 		util/iptables.c util/iptables.h			\
 		util/ebtables.c util/ebtables.h			\
 		util/dnsmasq.c util/dnsmasq.h                   \
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 6f14763..2ff7e0e 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -94,6 +94,7 @@ virCgroupKillPainfully;
 virCgroupKillRecursive;
 virCgroupMounted;
 virCgroupMoveTask;
+virCgroupNew;
 virCgroupPathOfController;
 virCgroupRemove;
 virCgroupSetBlkioDeviceWeight;
@@ -643,6 +644,11 @@ virHookInitialize;
 virHookPresent;
 
 
+# hotplug.h
+virHotplugUpdateCgroupCpuset;
+virHotplugSetCpusetToLastest;
+
+
 # interface_conf.h
 virInterfaceAssignDef;
 virInterfaceDefFormat;
diff --git a/src/util/cgroup.c b/src/util/cgroup.c
index 5dc0764..393d439 100644
--- a/src/util/cgroup.c
+++ b/src/util/cgroup.c
@@ -608,8 +608,8 @@ static int virCgroupMakeGroup(virCgroupPtr parent, virCgroupPtr group,
 }
 
 
-static int virCgroupNew(const char *path,
-                        virCgroupPtr *group)
+int virCgroupNew(const char *path,
+                 virCgroupPtr *group)
 {
     int rc = 0;
     char *typpath = NULL;
diff --git a/src/util/cgroup.h b/src/util/cgroup.h
index 68ac232..e294495 100644
--- a/src/util/cgroup.h
+++ b/src/util/cgroup.h
@@ -68,6 +68,9 @@ int virCgroupPathOfController(virCgroupPtr group,
                               const char *key,
                               char **path);
 
+int virCgroupNew(const char *path,
+                 virCgroupPtr *group);
+
 int virCgroupAddTask(virCgroupPtr group, pid_t pid);
 
 int virCgroupAddTaskController(virCgroupPtr group,
diff --git a/src/util/hotplug.c b/src/util/hotplug.c
new file mode 100644
index 0000000..7c44299
--- /dev/null
+++ b/src/util/hotplug.c
@@ -0,0 +1,240 @@
+/*
+ * Copyright (C) 2012 FUJITSU, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library;  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * Authors:
+ *     Tang Chen <tangchen cn fujitsu com>
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include "hotplug.h"
+#include "cgroup.h"
+#include "buf.h"
+#include "virterror_internal.h"
+#include "virnetlink.h"
+#include "logging.h"
+#include "memory.h"
+#include "util.h"
+
+#define VIR_FROM_THIS VIR_FROM_HOTPLUG
+
+#ifdef __linux__
+
+/**
+ * CPU hotplug message is of the following format:
+ * {online|offline}@/devices/system/cpu/cpuxx (xx is cpuid)
+ */
+# define CPU_ONLINE_MSG "online@/devices/system/cpu/cpu"
+# define CPU_OFFLINE_MSG "offline@/devices/system/cpu/cpu"
+
+/**
+ * virHotplugGetCpuidFromMsg:
+ *
+ * @msg: The buffer containing the received netlink message
+ * @length: The length of the received netlink message
+ * @cpuid: Contains the cpuid in the message
+ *
+ * This function get the cpuid from the following netlink message,
+ * {online|offline}@/devices/system/cpu/cpuxx (xx is cpuid)
+ *
+ * Returns 0 on success, or -1 on error.
+ */
+static int virHotplugGetCpuidFromMsg(unsigned char *msg,
+                                  int length,
+                                  char **cpuid)
+{
+    char *p = NULL;
+    size_t len_online = MIN(length, strlen(CPU_ONLINE_MSG));
+    size_t len_offline = MIN(length, strlen(CPU_OFFLINE_MSG));
+
+    if (VIR_ALLOC_N(*cpuid, 64) < 0)
+        goto memory_error;
+
+    /**
+     * For now, we aren't sure if the message is a '/0' ended string.
+     * So we only test the first len_online or len_offline characters.
+     */
+    if (strncmp((const char *)msg, CPU_ONLINE_MSG, len_online) == 0 ||
+        strncmp((const char *)msg, CPU_OFFLINE_MSG, len_offline) == 0) {
+        p = strrchr((const char *)msg, '/');
+        p = p + 4;
+        strcpy(*cpuid, p);
+        return 0;
+    } else {
+        VIR_DEBUG("Event is not a cpu hotplug event.");
+        VIR_FREE(*cpuid);
+        return 0;
+    }
+
+memory_error:
+    virReportOOMError();
+    return -1;
+}
+
+/**
+ * virHotplugUpdateCgroupCpuset:
+ *
+ * @msg: The buffer containing the received netlink message
+ * @length: The length of the received netlink message
+ * @cgroup: Contains a cgroup identifier to be modified
+ *
+ * Cpu hotplug netlink event handler. It is called when libvirtd
+ * receives netlink message from kernel, and modifies cpuset.cpus
+ * of specified cgroup.
+ *
+ * Return 0 on success.
+ */
+int
+virHotplugUpdateCgroupCpuset(unsigned char *msg,
+                             int length,
+                             virCgroupPtr cgroup)
+{
+    int rc = 0;
+    char *cpuid = NULL;
+    char *cpus = NULL;
+
+    if (!cgroup) {
+        virReportSystemError(EINVAL,
+                             "%s",
+                             _("invalid argument"));
+        return -EINVAL;
+    }
+
+    if (VIR_ALLOC_N(cpus, 1024) < 0) {
+        virReportOOMError();
+        return -ENOMEM;
+    }
+
+    rc = virHotplugGetCpuidFromMsg(msg, length, &cpuid);
+    if (rc < 0)
+        goto error;
+
+    /**
+     * If virHotplugGetCpuidFromMsg() succeeds, we are sure the
+     * netlink message is a '/0' ended string.
+     */
+    VIR_DEBUG("netlink (cpu hotplug): %s", msg);
+
+    if (msg == strstr((const char *)msg, "online")) {
+        VIR_DEBUG("CPU %s online message received.", cpuid);
+
+        if (virCgroupGetCpusetCpus(cgroup, &cpus) < 0) {
+            virReportSystemError(errno,
+                                 "%s",
+                                 _("Unable to get cpuset.cpus"));
+            rc = -1;
+            goto error;
+        }
+
+        if (virAsprintf(&cpus, "%s,%s", cpus, cpuid) < 0) {
+            virReportOOMError();
+            rc = -ENOMEM;
+            goto error;
+        }
+
+        if (virCgroupSetCpusetCpus(cgroup, cpus) < 0) {
+            virReportSystemError(errno,
+                                 "%s",
+                                 _("Unable to set cpuset.cpus"));
+            rc = -1;
+            goto error;
+        }
+
+    } else if (msg == strstr((const char *)msg, "offline")) {
+        /* For now, nothing to do. */
+        VIR_DEBUG("CPU %s offline message received.", cpuid);
+    }
+
+error:
+    VIR_FREE(cpuid);
+    VIR_FREE(cpus);
+
+    return rc;
+}
+
+/**
+ * virHotplugSetCpusetToLastest:
+ *
+ * @cgroup: The cgroup to be reset
+ *
+ * This function copies the cpuset from root to the specified cgroup.
+ *
+ * Return 0 on success or errno on error.
+ */
+int
+virHotplugSetCpusetToLastest(virCgroupPtr cgroup)
+{
+    int rc = 0;
+    char *cpus = NULL;
+    virCgroupPtr mpgrp = NULL;
+
+    /* mpgrp here is just the cpuset controller's mount point,
+     * which always contains all the online cpus.
+     */
+    rc = virCgroupNew("/", &mpgrp);
+    if (rc < 0)
+        goto out;
+
+    rc = virCgroupGetCpusetCpus(mpgrp, &cpus);
+    if (rc < 0)
+        goto error;
+
+    rc = virCgroupSetCpusetCpus(cgroup, cpus);
+    if (rc < 0)
+        goto error;
+    
+error:
+    virCgroupFree(&mpgrp);
+    VIR_FREE(cpus);
+
+out:
+    return rc;
+}
+
+#else
+
+static const char *unsupported = N_("Not a linux system.");
+
+/**
+ * virHotplugUpdateCgroupCpuset: This function is called when libvirtd
+ * receives netlink message from kernel, and modifies cpuset.cpus of
+ * specified cgroup.
+ */
+int
+virHotplugUpdateCgroupCpuset(unsigned char *msg ATTRIBUTE_UNUSED,
+                             int length ATTRIBUTE_UNUSED,
+                             virCgroupPtr cgroup ATTRIBUTE_UNUSED)
+{
+    VIR_DEBUG("%s", _(unsupported));
+    return 0;
+}
+
+/**
+ * virHotplugSetCpusetToLastest: This function copies the cpuset from
+ * root to the specified cgroup.
+ */
+int
+virHotplugSetCpusetToLastest(virCgroupPtr cgroup ATTRIBUTE_UNUSED)
+{
+    VIR_DEBUG("%s", _(unsupported));
+    return 0;
+}
+
+#endif /* __linux__ */
diff --git a/src/util/hotplug.h b/src/util/hotplug.h
new file mode 100644
index 0000000..ef3e279
--- /dev/null
+++ b/src/util/hotplug.h
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2012 FUJITSU, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library;  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * Authors:
+ *     Tang Chen <tangchen cn fujitsu com>
+ */
+
+#ifndef __HOTPLUG_H_
+# define __HOTPLUG_H_
+
+# include "internal.h"
+# include "cgroup.h"
+
+/**
+ * virHotplugUpdateCgroupCpuset: This function is called when libvirtd
+ * receives netlink message from kernel, and modifies cpuset.cpus of
+ * specified cgroup.
+ */
+int
+virHotplugUpdateCgroupCpuset(unsigned char *msg, int length,
+                             virCgroupPtr opaque);
+
+/**
+ * virHotplugSetCpusetToLastest: This function copies the cpuset from
+ * root to the specified cgroup.
+ */
+int
+virHotplugSetCpusetToLastest(virCgroupPtr cgroup);
+
+#endif
diff --git a/src/util/virterror.c b/src/util/virterror.c
index 7caa69e..eff52ad 100644
--- a/src/util/virterror.c
+++ b/src/util/virterror.c
@@ -115,7 +115,8 @@ VIR_ENUM_IMPL(virErrorDomain, VIR_ERR_DOMAIN_LAST,
               "Parallels Cloud Server",
               "Device Config",
 
-              "SSH transport layer" /* 50 */
+              "SSH transport layer", /* 50 */
+              "Hotplug driver" /* 51 */
     )
 
 
-- 
1.7.10.1


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