[Xen-changelog] [xen-unstable] x86: Disable IRQs and do WBINVD first in play_dead().

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir@xxxxxxx>
# Date 1299061403 0
# Node ID 666006a3a4ad3e4015fa0610aae6ebda3d271523
# Parent  bde351b18fd0fce23e6d4ae24627ed15a9b7c768
x86: Disable IRQs and do WBINVD first in play_dead().

When we advertise we are dead via cpu_exit_clear(), it is no longer
safe to handle interrupts as our per-cpu vars can go away.

In future, we may want to think about NMI handling in this scenario
too.

Signed-off-by: Keir Fraser <keir@xxxxxxx>
---


diff -r bde351b18fd0 -r 666006a3a4ad xen/arch/x86/domain.c
--- a/xen/arch/x86/domain.c     Wed Mar 02 10:01:55 2011 +0000
+++ b/xen/arch/x86/domain.c     Wed Mar 02 10:23:23 2011 +0000
@@ -99,19 +99,20 @@
 
 static void play_dead(void)
 {
+    local_irq_disable();
+    wbinvd();
+
     /*
      * NOTE: After cpu_exit_clear, per-cpu variables are no longer accessible,
      * as they may be freed at any time. In this case, heap corruption or
      * #PF can occur (when heap debugging is enabled). For example, even
      * printk() can involve tasklet scheduling, which touches per-cpu vars.
      * 
-     * Consider very carefully when adding code to this path. Most hypervisor
+     * Consider very carefully when adding code to *dead_idle. Most hypervisor
      * subsystems are unsafe to call.
      */
     cpu_exit_clear(smp_processor_id());
-    mb();
-    local_irq_disable();
-    wbinvd();
+
     (*dead_idle)();
 }
 

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