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, 83 insertions, 0 deletions

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 70375a690761..73d78dc9b875 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -674,6 +674,89 @@ static int retrigger_dynirq(unsigned int irq)
         return ret;
 }
 
+static void restore_cpu_virqs(unsigned int cpu)
+{
+        struct evtchn_bind_virq bind_virq;
+        int virq, irq, evtchn;
+
+        for (virq = 0; virq < NR_VIRQS; virq++) {
+                if ((irq = per_cpu(virq_to_irq, cpu)[virq]) == -1)
+                        continue;
+
+                BUG_ON(irq_info[irq].type != IRQT_VIRQ);
+                BUG_ON(irq_info[irq].index != virq);
+
+                /* Get a new binding from Xen. */
+                bind_virq.virq = virq;
+                bind_virq.vcpu = cpu;
+                if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
+                                                &bind_virq) != 0)
+                        BUG();
+                evtchn = bind_virq.port;
+
+                /* Record the new mapping. */
+                evtchn_to_irq[evtchn] = irq;
+                irq_info[irq] = mk_irq_info(IRQT_VIRQ, virq, evtchn);
+                bind_evtchn_to_cpu(evtchn, cpu);
+
+                /* Ready for use. */
+                unmask_evtchn(evtchn);
+        }
+}
+
+static void restore_cpu_ipis(unsigned int cpu)
+{
+        struct evtchn_bind_ipi bind_ipi;
+        int ipi, irq, evtchn;
+
+        for (ipi = 0; ipi < XEN_NR_IPIS; ipi++) {
+                if ((irq = per_cpu(ipi_to_irq, cpu)[ipi]) == -1)
+                        continue;
+
+                BUG_ON(irq_info[irq].type != IRQT_IPI);
+                BUG_ON(irq_info[irq].index != ipi);
+
+                /* Get a new binding from Xen. */
+                bind_ipi.vcpu = cpu;
+                if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_ipi,
+                                                &bind_ipi) != 0)
+                        BUG();
+                evtchn = bind_ipi.port;
+
+                /* Record the new mapping. */
+                evtchn_to_irq[evtchn] = irq;
+                irq_info[irq] = mk_irq_info(IRQT_IPI, ipi, evtchn);
+                bind_evtchn_to_cpu(evtchn, cpu);
+
+                /* Ready for use. */
+                unmask_evtchn(evtchn);
+
+        }
+}
+
+void xen_irq_resume(void)
+{
+        unsigned int cpu, irq, evtchn;
+
+        init_evtchn_cpu_bindings();
+
+        /* New event-channel space is not 'live' yet. */
+        for (evtchn = 0; evtchn < NR_EVENT_CHANNELS; evtchn++)
+                mask_evtchn(evtchn);
+
+        /* No IRQ <-> event-channel mappings. */
+        for (irq = 0; irq < NR_IRQS; irq++)
+                irq_info[irq].evtchn = 0; /* zap event-channel binding */
+
+        for (evtchn = 0; evtchn < NR_EVENT_CHANNELS; evtchn++)
+                evtchn_to_irq[evtchn] = -1;
+
+        for_each_possible_cpu(cpu) {
+                restore_cpu_virqs(cpu);
+                restore_cpu_ipis(cpu);
+        }
+}
+
 static struct irq_chip xen_dynamic_chip __read_mostly = {
         .name           = "xen-dyn",
         .mask           = disable_dynirq,