[PATCH] x86 ACPI: Fix breakage of resume on 64-bit UP systems with SMP kernel

From: Rafael J. Wysocki
Date: Thu Oct 16 2008 - 19:22:28 EST

From: Rafael J. Wysocki <rjw@xxxxxxx>

x86 ACPI: Fix breakage of resume on 64-bit UP systems with SMP kernel

We are now using per CPU GDT tables in head_64.S and the original
early_gdt_descr.address is invalidated after boot by
setup_per_cpu_areas(). This breaks resume from suspend to RAM on
x86_64 UP systems using SMP kernels, because this part of head_64.S
is also executed during the resume and the invalid GDT address
causes the system to crash. It doesn't break on 'true' SMP systems,
because early_gdt_descr.address is modified every time
native_cpu_up() runs. However, during resume it should point to the
GDT of the boot CPU rather than to another CPU's GDT.

For this reason, during suspend to RAM always make
early_gdt_descr.address point to the boot CPU's GDT.

This fixes http://bugzilla.kernel.org/show_bug.cgi?id=11568, which
is a regression from 2.6.26.

Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
Reported-and-tested-by: Andy Wettstein <ajw1980@xxxxxxxxx>
arch/x86/kernel/acpi/sleep.c | 3 +++
1 file changed, 3 insertions(+)

Index: linux-2.6/arch/x86/kernel/acpi/sleep.c
--- linux-2.6.orig/arch/x86/kernel/acpi/sleep.c
+++ linux-2.6/arch/x86/kernel/acpi/sleep.c
@@ -10,6 +10,7 @@
#include <linux/dmi.h>
#include <linux/cpumask.h>
#include <asm/segment.h>
+#include <asm/desc.h>

#include "realmode/wakeup.h"
#include "sleep.h"
@@ -100,6 +101,8 @@ int acpi_save_state_mem(void)
header->trampoline_segment = setup_trampoline() >> 4;
stack_start.sp = temp_stack + 4096;
+ early_gdt_descr.address =
+ (unsigned long)get_cpu_gdt_table(smp_processor_id());
initial_code = (unsigned long)wakeup_long64;
saved_magic = 0x123456789abcdef0;
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