xen: handle external requests for shutdown, reboot and sysrq

The guest domain can be asked to shutdown or reboot itself, or have a
sysrq key injected, via xenbus.  This patch adds a watcher for those
events, and does the appropriate action.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Chris Wright <chrisw@sous-sol.org>

2 files changed, 144 insertions, 1 deletions

diff --git a/arch/i386/xen/Makefile b/arch/i386/xen/Makefile
index fd05f243a3f8..7bf2ce399a2a 100644
--- a/arch/i386/xen/Makefile
+++ b/arch/i386/xen/Makefile
@@ -1,4 +1,4 @@
 obj-y           := enlighten.o setup.o features.o multicalls.o mmu.o \
-                        events.o time.o
+                        events.o time.o manage.o
 
 obj-$(CONFIG_SMP)       += smp.o
diff --git a/arch/i386/xen/manage.c b/arch/i386/xen/manage.c
new file mode 100644
index 000000000000..aa7af9e6abc0
--- /dev/null
+++ b/arch/i386/xen/manage.c
@@ -0,0 +1,143 @@
+/*
+ * Handle extern requests for shutdown, reboot and sysrq
+ */
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <linux/reboot.h>
+#include <linux/sysrq.h>
+
+#include <xen/xenbus.h>
+
+#define SHUTDOWN_INVALID  -1
+#define SHUTDOWN_POWEROFF  0
+#define SHUTDOWN_SUSPEND   2
+/* Code 3 is SHUTDOWN_CRASH, which we don't use because the domain can only
+ * report a crash, not be instructed to crash!
+ * HALT is the same as POWEROFF, as far as we're concerned.  The tools use
+ * the distinction when we return the reason code to them.
+ */
+#define SHUTDOWN_HALT      4
+
+/* Ignore multiple shutdown requests. */
+static int shutting_down = SHUTDOWN_INVALID;
+
+static void shutdown_handler(struct xenbus_watch *watch,
+                             const char **vec, unsigned int len)
+{
+        char *str;
+        struct xenbus_transaction xbt;
+        int err;
+
+        if (shutting_down != SHUTDOWN_INVALID)
+                return;
+
+ again:
+        err = xenbus_transaction_start(&xbt);
+        if (err)
+                return;
+
+        str = (char *)xenbus_read(xbt, "control", "shutdown", NULL);
+        /* Ignore read errors and empty reads. */
+        if (XENBUS_IS_ERR_READ(str)) {
+                xenbus_transaction_end(xbt, 1);
+                return;
+        }
+
+        xenbus_write(xbt, "control", "shutdown", "");
+
+        err = xenbus_transaction_end(xbt, 0);
+        if (err == -EAGAIN) {
+                kfree(str);
+                goto again;
+        }
+
+        if (strcmp(str, "poweroff") == 0 ||
+            strcmp(str, "halt") == 0)
+                orderly_poweroff(false);
+        else if (strcmp(str, "reboot") == 0)
+                ctrl_alt_del();
+        else {
+                printk(KERN_INFO "Ignoring shutdown request: %s\n", str);
+                shutting_down = SHUTDOWN_INVALID;
+        }
+
+        kfree(str);
+}
+
+static void sysrq_handler(struct xenbus_watch *watch, const char **vec,
+                          unsigned int len)
+{
+        char sysrq_key = '\0';
+        struct xenbus_transaction xbt;
+        int err;
+
+ again:
+        err = xenbus_transaction_start(&xbt);
+        if (err)
+                return;
+        if (!xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key)) {
+                printk(KERN_ERR "Unable to read sysrq code in "
+                       "control/sysrq\n");
+                xenbus_transaction_end(xbt, 1);
+                return;
+        }
+
+        if (sysrq_key != '\0')
+                xenbus_printf(xbt, "control", "sysrq", "%c", '\0');
+
+        err = xenbus_transaction_end(xbt, 0);
+        if (err == -EAGAIN)
+                goto again;
+
+        if (sysrq_key != '\0')
+                handle_sysrq(sysrq_key, NULL);
+}
+
+static struct xenbus_watch shutdown_watch = {
+        .node = "control/shutdown",
+        .callback = shutdown_handler
+};
+
+static struct xenbus_watch sysrq_watch = {
+        .node = "control/sysrq",
+        .callback = sysrq_handler
+};
+
+static int setup_shutdown_watcher(void)
+{
+        int err;
+
+        err = register_xenbus_watch(&shutdown_watch);
+        if (err) {
+                printk(KERN_ERR "Failed to set shutdown watcher\n");
+                return err;
+        }
+
+        err = register_xenbus_watch(&sysrq_watch);
+        if (err) {
+                printk(KERN_ERR "Failed to set sysrq watcher\n");
+                return err;
+        }
+
+        return 0;
+}
+
+static int shutdown_event(struct notifier_block *notifier,
+                          unsigned long event,
+                          void *data)
+{
+        setup_shutdown_watcher();
+        return NOTIFY_DONE;
+}
+
+static int __init setup_shutdown_event(void)
+{
+        static struct notifier_block xenstore_notifier = {
+                .notifier_call = shutdown_event
+        };
+        register_xenstore_notifier(&xenstore_notifier);
+
+        return 0;
+}
+
+subsys_initcall(setup_shutdown_event);