[PATCH] restore sysenter MSRs at APM resume

This changes apm.c to invoke suspend.c's save and restore processor
state procedures around suspends, which fixes the SYSENTER MSR problem.

The patch also decouples sysenter.c from SOFTWARE_SUSPEND: the variables
used (only!) in suspend_asm.S are moved there, and the include file now
declares the procedures called from apm.c (previously they were only
called from suspend_asm.S).

arch/i386/kernel/Makefile

@@ -17,7 +17,7 @@ obj-$(CONFIG_MCA)		+= mca.o
 obj-$(CONFIG_X86_MSR)		+= msr.o
 obj-$(CONFIG_X86_CPUID)		+= cpuid.o
 obj-$(CONFIG_MICROCODE)		+= microcode.o
-obj-$(CONFIG_APM)		+= apm.o
+obj-$(CONFIG_APM)		+= apm.o suspend.o
 obj-$(CONFIG_X86_SMP)		+= smp.o smpboot.o
 obj-$(CONFIG_X86_TRAMPOLINE)	+= trampoline.o
 obj-$(CONFIG_X86_MPPARSE)	+= mpparse.o

arch/i386/kernel/apm.c

@@ -226,6 +226,7 @@
 #include <asm/system.h>
 #include <asm/uaccess.h>
 #include <asm/desc.h>
+#include <asm/suspend.h>
 
 #include "io_ports.h"
 
@@ -1212,7 +1213,9 @@ static int suspend(int vetoable)
 	spin_unlock(&i8253_lock);
 	write_sequnlock_irq(&xtime_lock);
 
+	save_processor_state();
 	err = set_system_power_state(APM_STATE_SUSPEND);
+	restore_processor_state();
 
 	write_seqlock_irq(&xtime_lock);
 	spin_lock(&i8253_lock);

arch/i386/kernel/suspend.c

@@ -27,9 +27,7 @@
 #include <asm/tlbflush.h>
 
 static struct saved_context saved_context;
-unsigned long saved_context_eax, saved_context_ebx, saved_context_ecx, saved_context_edx;
-unsigned long saved_context_esp, saved_context_ebp, saved_context_esi, saved_context_edi;
-unsigned long saved_context_eflags;
+static void fix_processor_context(void);
 
 extern void enable_sep_cpu(void *);
 
@@ -107,7 +105,7 @@ void restore_processor_state(void)
 	do_fpu_end();
 }
 
-void fix_processor_context(void)
+static void fix_processor_context(void)
 {
 	int cpu = smp_processor_id();
 	struct tss_struct * t = init_tss + cpu;

arch/i386/kernel/suspend_asm.S

@@ -6,6 +6,28 @@
 #include <asm/segment.h>
 #include <asm/page.h>
 
+	.data
+saved_context_eax:
+	.long	0
+saved_context_ebx:
+	.long	0
+saved_context_ecx:
+	.long	0
+saved_context_edx:
+	.long	0
+saved_context_esp:
+	.long	0
+saved_context_ebp:
+	.long	0
+saved_context_esi:
+	.long	0
+saved_context_edi:
+	.long	0
+saved_context_eflags:
+	.long	0
+
+	.text
+
 ENTRY(do_magic)
 	pushl %ebx
 	cmpl $0,8(%esp)

include/asm-i386/suspend.h

@@ -30,18 +30,14 @@ struct saved_context {
 	unsigned long return_address;
 } __attribute__((packed));
 
-/* We'll access these from assembly, so we'd better have them outside struct */
-extern unsigned long saved_context_eax, saved_context_ebx, saved_context_ecx, saved_context_edx;
-extern unsigned long saved_context_esp, saved_context_ebp, saved_context_esi, saved_context_edi;
-extern unsigned long saved_context_eflags;
-
-
 #define loaddebug(thread,register) \
                __asm__("movl %0,%%db" #register  \
                        : /* no output */ \
                        :"r" ((thread)->debugreg[register]))
 
-extern void fix_processor_context(void);
+extern void save_processor_state(void);
+extern void restore_processor_state(void);
+
 extern void do_magic(int resume);
 
 #ifdef CONFIG_ACPI_SLEEP