[PATCH RFC v2 5/5] x86/mwait-idle: squash stats update when not actually entering C-state

[Jan Beulich]

While we don't want to skip calling update_idle_stats(), arrange for it
to not increment the overall time spent in the state we didn't really
enter.

Signed-off-by: Jan Beulich <jbeul...@suse.com>
---
RFC: Arguably more of what follows could be moved into the if() -
     thoughts?
---
v2: New.

--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -861,9 +861,11 @@ static void mwait_idle(void)
                mwait_idle_with_hints(cx->address, MWAIT_ECX_INTERRUPT_BREAK);
 
                local_irq_disable();
-       }
 
-       after = alternative_call(cpuidle_get_tick);
+               after = alternative_call(cpuidle_get_tick);
+       }
+       else
+               before = after = alternative_call(cpuidle_get_tick);
 
        cstate_restore_tsc();
        trace_exit_reason(irq_traced);