context_tracking: Move guest exit context tracking to separate helpers

Provide separate context tracking helpers for guest exit, the standalone
helpers will be called separately by KVM x86 in later patches to fix
tick-based accounting.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210505002735.1684165-2-seanjc@google.com

Author: Wanpeng Li

include/linux/context_tracking.h

@@ -131,10 +131,15 @@ static __always_inline void guest_enter_irqoff(void)
 	}
 }
 
-static __always_inline void guest_exit_irqoff(void)
+static __always_inline void context_tracking_guest_exit(void)
 {
 	if (context_tracking_enabled())
 		__context_tracking_exit(CONTEXT_GUEST);
+}
+
+static __always_inline void guest_exit_irqoff(void)
+{
+	context_tracking_guest_exit();
 
 	instrumentation_begin();
 	if (vtime_accounting_enabled_this_cpu())
@@ -159,6 +164,8 @@ static __always_inline void guest_enter_irqoff(void)
 	instrumentation_end();
 }
 
+static __always_inline void context_tracking_guest_exit(void) { }
+
 static __always_inline void guest_exit_irqoff(void)
 {
 	instrumentation_begin();