xen: restore vcpu_info mapping

If we're using vcpu_info mapping, then make sure its restored on all
processors before relasing them from stop_machine.

The only complication is that if this fails, we can't continue because
we've already made assumptions that the mapping is available (baked in
calls to the _direct versions of the functions, for example).

Fortunately this can only happen with a 32-bit hypervisor, which may
possibly run out of mapping space.  On a 64-bit hypervisor, this is a
non-issue.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 29 insertions, 1 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index ed9f04b3836d..8e6152e6ed88 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -98,7 +98,7 @@ struct shared_info *HYPERVISOR_shared_info = (void *)&xen_dummy_shared_info;
  */
 static int have_vcpu_info_placement = 1;
 
-static void __init xen_vcpu_setup(int cpu)
+static void xen_vcpu_setup(int cpu)
 {
         struct vcpu_register_vcpu_info info;
         int err;
@@ -136,6 +136,34 @@ static void __init xen_vcpu_setup(int cpu)
         }
 }
 
+/*
+ * On restore, set the vcpu placement up again.
+ * If it fails, then we're in a bad state, since
+ * we can't back out from using it...
+ */
+void xen_vcpu_restore(void)
+{
+        if (have_vcpu_info_placement) {
+                int cpu;
+
+                for_each_online_cpu(cpu) {
+                        bool other_cpu = (cpu != smp_processor_id());
+
+                        if (other_cpu &&
+                            HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL))
+                                BUG();
+
+                        xen_vcpu_setup(cpu);
+
+                        if (other_cpu &&
+                            HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL))
+                                BUG();
+                }
+
+                BUG_ON(!have_vcpu_info_placement);
+        }
+}
+
 static void __init xen_banner(void)
 {
         printk(KERN_INFO "Booting paravirtualized kernel on %s\n",