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authorAlex Nixon <alex.nixon@citrix.com>2008-08-22 14:52:15 +0400
committerIngo Molnar <mingo@elte.hu>2008-08-25 13:25:14 +0400
commitd68d82afd4c88e25763b23cd9cd4974573a3706f (patch)
tree42a3fb93a5cef70db7ad01fda1ed0dc68dbe6110 /drivers/xen/cpu_hotplug.c
parent8227dce7dc2cfdcc28ee0eadfb482a7ee77fba03 (diff)
downloadlinux-d68d82afd4c88e25763b23cd9cd4974573a3706f.tar.xz
xen: implement CPU hotplugging
Note the changes from 2.6.18-xen CPU hotplugging: A vcpu_down request from the remote admin via Xenbus both hotunplugs the CPU, and disables it by removing it from the cpu_present map, and removing its entry in /sys. A vcpu_up request from the remote admin only re-enables the CPU, and does not immediately bring the CPU up. A udev event is emitted, which can be caught by the user if he wishes to automatically re-up CPUs when available, or implement a more complex policy. Signed-off-by: Alex Nixon <alex.nixon@citrix.com> Acked-by: Jeremy Fitzhardinge <jeremy@goop.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'drivers/xen/cpu_hotplug.c')
-rw-r--r--drivers/xen/cpu_hotplug.c90
1 files changed, 90 insertions, 0 deletions
diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
new file mode 100644
index 000000000000..1bc003536cdb
--- /dev/null
+++ b/drivers/xen/cpu_hotplug.c
@@ -0,0 +1,90 @@
+#include <linux/notifier.h>
+
+#include <xen/xenbus.h>
+
+#include <asm-x86/xen/hypervisor.h>
+#include <asm/cpu.h>
+
+static void enable_hotplug_cpu(int cpu)
+{
+ if (!cpu_present(cpu))
+ arch_register_cpu(cpu);
+
+ cpu_set(cpu, cpu_present_map);
+}
+
+static void disable_hotplug_cpu(int cpu)
+{
+ if (cpu_present(cpu))
+ arch_unregister_cpu(cpu);
+
+ cpu_clear(cpu, cpu_present_map);
+}
+
+static void vcpu_hotplug(unsigned int cpu)
+{
+ int err;
+ char dir[32], state[32];
+
+ if (!cpu_possible(cpu))
+ return;
+
+ sprintf(dir, "cpu/%u", 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) {
+ enable_hotplug_cpu(cpu);
+ } else if (strcmp(state, "offline") == 0) {
+ (void)cpu_down(cpu);
+ disable_hotplug_cpu(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)
+{
+ unsigned int cpu;
+ char *cpustr;
+ const char *node = vec[XS_WATCH_PATH];
+
+ cpustr = strstr(node, "cpu/");
+ if (cpustr != NULL) {
+ sscanf(cpustr, "cpu/%u", &cpu);
+ vcpu_hotplug(cpu);
+ }
+}
+
+static int setup_cpu_watcher(struct notifier_block *notifier,
+ unsigned long event, void *data)
+{
+ static struct xenbus_watch cpu_watch = {
+ .node = "cpu",
+ .callback = handle_vcpu_hotplug_event};
+
+ (void)register_xenbus_watch(&cpu_watch);
+
+ return NOTIFY_DONE;
+}
+
+static int __init setup_vcpu_hotplug_event(void)
+{
+ static struct notifier_block xsn_cpu = {
+ .notifier_call = setup_cpu_watcher };
+
+ if (!is_running_on_xen())
+ return -ENODEV;
+
+ register_xenstore_notifier(&xsn_cpu);
+
+ return 0;
+}
+
+arch_initcall(setup_vcpu_hotplug_event);
+