This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / drivers / xen / core / cpu_hotplug.c

diff --git a/drivers/xen/core/cpu_hotplug.c b/drivers/xen/core/cpu_hotplug.c
new file mode 100644 (file)
index 0000000..0969e21
--- /dev/null
+++ b/drivers/xen/core/cpu_hotplug.c
@@ -0,0 +1,188 @@
+#include <linux/config.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>
+#include <xen/cpu_hotplug.h>
+#include <xen/xenbus.h>
+
+/*
+ * Set of CPUs that remote admin software will allow us to bring online.
+ * Notified to us via xenbus.
+ */
+static cpumask_t xenbus_allowed_cpumask;
+
+/* Set of CPUs that local admin will allow us to bring online. */
+static cpumask_t local_allowed_cpumask = CPU_MASK_ALL;
+
+static int local_cpu_hotplug_request(void)
+{
+       /*
+        * We assume a CPU hotplug request comes from local admin if it is made
+        * via a userspace process (i.e., one with a real mm_struct).
+        */
+       return (current->mm != NULL);
+}
+
+static void vcpu_hotplug(unsigned int cpu)
+{
+       int err;
+       char dir[32], state[32];
+
+       if ((cpu >= NR_CPUS) || !cpu_possible(cpu))
+               return;
+
+       sprintf(dir, "cpu/%d", cpu);
+       err = xenbus_scanf(XBT_NIL, dir, "availability", "%s", state);
+       if (err != 1) {
+               printk(KERN_ERR "XENBUS: Unable to read cpu state\n");
+               return;
+       }
+
+       if (strcmp(state, "online") == 0) {
+               cpu_set(cpu, xenbus_allowed_cpumask);
+               (void)cpu_up(cpu);
+       } else if (strcmp(state, "offline") == 0) {
+               cpu_clear(cpu, xenbus_allowed_cpumask);
+               (void)cpu_down(cpu);
+       } else {
+               printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n",
+                      state, cpu);
+       }
+}
+
+static void handle_vcpu_hotplug_event(
+       struct xenbus_watch *watch, const char **vec, unsigned int len)
+{
+       int cpu;
+       char *cpustr;
+       const char *node = vec[XS_WATCH_PATH];
+
+       if ((cpustr = strstr(node, "cpu/")) != NULL) {
+               sscanf(cpustr, "cpu/%d", &cpu);
+               vcpu_hotplug(cpu);
+       }
+}
+
+static int smpboot_cpu_notify(struct notifier_block *notifier,
+                             unsigned long action, void *hcpu)
+{
+       int cpu = (long)hcpu;
+
+       /*
+        * We do this in a callback notifier rather than __cpu_disable()
+        * because local_cpu_hotplug_request() does not work in the latter
+        * as it's always executed from within a stopmachine kthread.
+        */
+       if ((action == CPU_DOWN_PREPARE) && local_cpu_hotplug_request())
+               cpu_clear(cpu, local_allowed_cpumask);
+
+       return NOTIFY_OK;
+}
+
+static int setup_cpu_watcher(struct notifier_block *notifier,
+                             unsigned long event, void *data)
+{
+       int i;
+
+       static struct xenbus_watch cpu_watch = {
+               .node = "cpu",
+               .callback = handle_vcpu_hotplug_event,
+               .flags = XBWF_new_thread };
+       (void)register_xenbus_watch(&cpu_watch);
+
+       if (!(xen_start_info->flags & SIF_INITDOMAIN)) {
+               for_each_cpu(i)
+                       vcpu_hotplug(i);
+               printk(KERN_INFO "Brought up %ld CPUs\n",
+                      (long)num_online_cpus());
+       }
+
+       return NOTIFY_DONE;
+}
+
+static int __init setup_vcpu_hotplug_event(void)
+{
+       static struct notifier_block hotplug_cpu = {
+               .notifier_call = smpboot_cpu_notify };
+       static struct notifier_block xsn_cpu = {
+               .notifier_call = setup_cpu_watcher };
+
+       if (!is_running_on_xen())
+               return -ENODEV;
+
+       register_cpu_notifier(&hotplug_cpu);
+       register_xenstore_notifier(&xsn_cpu);
+
+       return 0;
+}
+
+arch_initcall(setup_vcpu_hotplug_event);
+
+int smp_suspend(void)
+{
+       int i, err;
+
+       lock_cpu_hotplug();
+
+       /*
+        * Take all other CPUs offline. We hold the hotplug mutex to
+        * avoid other processes bringing up CPUs under our feet.
+        */
+       while (num_online_cpus() > 1) {
+               unlock_cpu_hotplug();
+               for_each_online_cpu(i) {
+                       if (i == 0)
+                               continue;
+                       err = cpu_down(i);
+                       if (err) {
+                               printk(KERN_CRIT "Failed to take all CPUs "
+                                      "down: %d.\n", err);
+                               for_each_cpu(i)
+                                       vcpu_hotplug(i);
+                               return err;
+                       }
+               }
+               lock_cpu_hotplug();
+       }
+
+       return 0;
+}
+
+void smp_resume(void)
+{
+       int cpu;
+
+       for_each_cpu(cpu)
+               cpu_initialize_context(cpu);
+
+       unlock_cpu_hotplug();
+
+       for_each_cpu(cpu)
+               vcpu_hotplug(cpu);
+}
+
+int cpu_up_check(unsigned int cpu)
+{
+       int rc = 0;
+
+       if (local_cpu_hotplug_request()) {
+               cpu_set(cpu, local_allowed_cpumask);
+               if (!cpu_isset(cpu, xenbus_allowed_cpumask)) {
+                       printk("%s: attempt to bring up CPU %u disallowed by "
+                              "remote admin.\n", __FUNCTION__, cpu);
+                       rc = -EBUSY;
+               }
+       } else if (!cpu_isset(cpu, local_allowed_cpumask) ||
+                  !cpu_isset(cpu, xenbus_allowed_cpumask)) {
+               rc = -EBUSY;
+       }
+
+       return rc;
+}
+
+void init_xenbus_allowed_cpumask(void)
+{
+       xenbus_allowed_cpumask = cpu_present_map;
+}