[Xen-changelog] [xen-unstable] x86: Fix cpu offline bug: cancel SYSIO method when play dead

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Liu, Jinsong <jinsong.liu@xxxxxxxxx>
# Date 1299860853 0
# Node ID 6c5e68521f1dc5c55efd11f9d0a29a9f6666191e
# Parent  da7c950772ed1e62c3ea6a888d139adab6cb8fca
x86: Fix cpu offline bug: cancel SYSIO method when play dead

Play dead is a fragile and tricky point of cpu offline logic.  For how
to play cpu dead, linux kernel changed several times: Very old kernel
support 3 ways to play cpu dead: mwait, SYSIO, and halt, just like
what cpuidle did when enter C3; Later, it cancel mwait and SYSIO
support, only use halt to play dead; Latest linux 2.6.38 add mwait
support when cpu dead.

This patch cancel SYSIO method when cpu dead, keep same with latest
kernel.

SYSIO is an obsoleted method to enter deep C, with some tricky
hardware behavior, and seldom supported in new platform.  Xen
experiment indicate that when cpu dead, SYSIO method would trigger
unknown issue which would bring strange error.  We now cancel SYSIO
method when cpu dead, after all, correctness is more important than
power save, and btw new platform use mwait.

Signed-off-by: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
---


diff -r da7c950772ed -r 6c5e68521f1d xen/arch/x86/acpi/cpu_idle.c
--- a/xen/arch/x86/acpi/cpu_idle.c      Fri Mar 11 16:20:34 2011 +0000
+++ b/xen/arch/x86/acpi/cpu_idle.c      Fri Mar 11 16:27:33 2011 +0000
@@ -554,7 +554,6 @@
 {
     struct acpi_processor_power *power;
     struct acpi_processor_cx *cx;
-    int unused;
 
     if ( (power = processor_powers[smp_processor_id()]) == NULL )
         goto default_halt;
@@ -574,10 +573,6 @@
                 __monitor((void *)&mwait_wakeup(smp_processor_id()), 0, 0);
                 __mwait(cx->address, 0);
                 break;
-            case ACPI_CSTATE_EM_SYSIO:
-                inb(cx->address);
-                unused = inl(pmtmr_ioport);
-                break;
             default:
                 goto default_halt;
         }

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