x86: kvmclock: abstract save/restore sched_clock_state

Upon resume from hibernation, CPU 0's hvclock area contains the old
values for system_time and tsc_timestamp. It is necessary for the
hypervisor to update these values with uptodate ones before the CPU uses
them.

Abstract TSC's save/restore sched_clock_state functions and use
restore_state to write to KVM_SYSTEM_TIME MSR, forcing an update.

Also move restore_sched_clock_state before __restore_processor_state,
since the later calls CONFIG_LOCK_STAT's lockstat_clock (also for TSC).
Thanks to Igor Mammedov for tracking it down.

Fixes suspend-to-disk with kvmclock.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 15d9915..c91e8b9 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -61,7 +61,7 @@
 extern void check_tsc_sync_target(void);
 
 extern int notsc_setup(char *);
-extern void save_sched_clock_state(void);
-extern void restore_sched_clock_state(void);
+extern void tsc_save_sched_clock_state(void);
+extern void tsc_restore_sched_clock_state(void);
 
 #endif /* _ASM_X86_TSC_H */