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@intel.com>

diff --git a/xen/arch/x86/acpi/cpu_idle.c b/xen/arch/x86/acpi/cpu_idle.c
index 7cbcceeb7a75cef8397bf9edbaee5a8ea7b4bc46..a01a27f4add8907cb8b6750a648b478d375d79d8 100644 (file)
--- a/xen/arch/x86/acpi/cpu_idle.c
+++ b/xen/arch/x86/acpi/cpu_idle.c
@@ -554,7 +554,6 @@ static void acpi_dead_idle(void)
 {
     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 @@ static void acpi_dead_idle(void)
                 __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;
         }