xen: implement save/restore

This patch implements Xen save/restore and migration.

Saving is triggered via xenbus, which is polled in
drivers/xen/manage.c.  When a suspend request comes in, the kernel
prepares itself for saving by:

1 - Freeze all processes.  This is primarily to prevent any
    partially-completed pagetable updates from confusing the suspend
    process.  If CONFIG_PREEMPT isn't defined, then this isn't necessary.

2 - Suspend xenbus and other devices

3 - Stop_machine, to make sure all the other vcpus are quiescent.  The
    Xen tools require the domain to run its save off vcpu0.

4 - Within the stop_machine state, it pins any unpinned pgds (under
    construction or destruction), performs canonicalizes various other
    pieces of state (mostly converting mfns to pfns), and finally

5 - Suspend the domain

Restore reverses the steps used to save the domain, ending when all
the frozen processes are thawed.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 112 insertions, 14 deletions

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index aa7af9e6abc0..ba85fa2cff33 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -5,21 +5,113 @@
 #include <linux/err.h>
 #include <linux/reboot.h>
 #include <linux/sysrq.h>
+#include <linux/stop_machine.h>
+#include <linux/freezer.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
+#include <xen/grant_table.h>
+#include <xen/events.h>
+#include <xen/hvc-console.h>
+#include <xen/xen-ops.h>
+
+#include <asm/xen/hypercall.h>
+#include <asm/xen/page.h>
+
+enum shutdown_state {
+        SHUTDOWN_INVALID = -1,
+        SHUTDOWN_POWEROFF = 0,
+        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.  */
+         SHUTDOWN_HALT = 4,
+};
 
 /* Ignore multiple shutdown requests. */
-static int shutting_down = SHUTDOWN_INVALID;
+static enum shutdown_state shutting_down = SHUTDOWN_INVALID;
+
+static int xen_suspend(void *data)
+{
+        int *cancelled = data;
+
+        BUG_ON(!irqs_disabled());
+
+        load_cr3(swapper_pg_dir);
+
+        xen_mm_pin_all();
+        gnttab_suspend();
+        xen_time_suspend();
+        xen_pre_suspend();
+
+        /*
+         * This hypercall returns 1 if suspend was cancelled
+         * or the domain was merely checkpointed, and 0 if it
+         * is resuming in a new domain.
+         */
+        *cancelled = HYPERVISOR_suspend(virt_to_mfn(xen_start_info));
+
+        xen_post_suspend(*cancelled);
+        xen_time_resume();
+        gnttab_resume();
+        xen_mm_unpin_all();
+
+        if (!*cancelled) {
+                xen_irq_resume();
+                xen_console_resume();
+        }
+
+        return 0;
+}
+
+static void do_suspend(void)
+{
+        int err;
+        int cancelled = 1;
+
+        shutting_down = SHUTDOWN_SUSPEND;
+
+#ifdef CONFIG_PREEMPT
+        /* If the kernel is preemptible, we need to freeze all the processes
+           to prevent them from being in the middle of a pagetable update
+           during suspend. */
+        err = freeze_processes();
+        if (err) {
+                printk(KERN_ERR "xen suspend: freeze failed %d\n", err);
+                return;
+        }
+#endif
+
+        err = device_suspend(PMSG_SUSPEND);
+        if (err) {
+                printk(KERN_ERR "xen suspend: device_suspend %d\n", err);
+                goto out;
+        }
+
+        printk("suspending xenbus...\n");
+        /* XXX use normal device tree? */
+        xenbus_suspend();
+
+        err = stop_machine_run(xen_suspend, &cancelled, 0);
+        if (err) {
+                printk(KERN_ERR "failed to start xen_suspend: %d\n", err);
+                goto out;
+        }
+
+        if (!cancelled)
+                xenbus_resume();
+        else
+                xenbus_suspend_cancel();
+
+        device_resume();
+
+
+out:
+#ifdef CONFIG_PREEMPT
+        thaw_processes();
+#endif
+        shutting_down = SHUTDOWN_INVALID;
+}
 
 static void shutdown_handler(struct xenbus_watch *watch,
                              const char **vec, unsigned int len)
@@ -52,11 +144,17 @@ static void shutdown_handler(struct xenbus_watch *watch,
         }
 
         if (strcmp(str, "poweroff") == 0 ||
-            strcmp(str, "halt") == 0)
+            strcmp(str, "halt") == 0) {
+                shutting_down = SHUTDOWN_POWEROFF;
                 orderly_poweroff(false);
-        else if (strcmp(str, "reboot") == 0)
+        } else if (strcmp(str, "reboot") == 0) {
+                shutting_down = SHUTDOWN_POWEROFF; /* ? */
                 ctrl_alt_del();
-        else {
+#ifdef CONFIG_PM_SLEEP
+        } else if (strcmp(str, "suspend") == 0) {
+                do_suspend();
+#endif
+        } else {
                 printk(KERN_INFO "Ignoring shutdown request: %s\n", str);
                 shutting_down = SHUTDOWN_INVALID;
         }