cputime: Use a proper subsystem naming for vtime related APIs

Use a naming based on vtime as a prefix for virtual based
cputime accounting APIs:

- account_system_vtime() -> vtime_account()
- account_switch_vtime() -> vtime_task_switch()

It makes it easier to allow for further declension such
as vtime_account_system(), vtime_account_idle(), ... if we
want to find out the context we account to from generic code.

This also make it better to know on which subsystem these APIs
refer to.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 305f23c..cab3da3 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -132,11 +132,11 @@
 struct task_struct;
 
 #if !defined(CONFIG_VIRT_CPU_ACCOUNTING) && !defined(CONFIG_IRQ_TIME_ACCOUNTING)
-static inline void account_system_vtime(struct task_struct *tsk)
+static inline void vtime_account(struct task_struct *tsk)
 {
 }
 #else
-extern void account_system_vtime(struct task_struct *tsk);
+extern void vtime_account(struct task_struct *tsk);
 #endif
 
 #if defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU)
@@ -162,7 +162,7 @@
  */
 #define __irq_enter()					\
 	do {						\
-		account_system_vtime(current);		\
+		vtime_account(current);		\
 		add_preempt_count(HARDIRQ_OFFSET);	\
 		trace_hardirq_enter();			\
 	} while (0)
@@ -178,7 +178,7 @@
 #define __irq_exit()					\
 	do {						\
 		trace_hardirq_exit();			\
-		account_system_vtime(current);		\
+		vtime_account(current);		\
 		sub_preempt_count(HARDIRQ_OFFSET);	\
 	} while (0)
 
diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index bbe5d15..ca0944b 100644
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -131,9 +131,9 @@
 extern void account_idle_ticks(unsigned long ticks);
 
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
-extern void account_switch_vtime(struct task_struct *prev);
+extern void vtime_task_switch(struct task_struct *prev);
 #else
-static inline void account_switch_vtime(struct task_struct *prev) { }
+static inline void vtime_task_switch(struct task_struct *prev) { }
 #endif
 
 #endif /* _LINUX_KERNEL_STAT_H */
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b70b48b..8a59e0a 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -685,7 +685,7 @@
 static inline void kvm_guest_enter(void)
 {
 	BUG_ON(preemptible());
-	account_system_vtime(current);
+	vtime_account(current);
 	current->flags |= PF_VCPU;
 	/* KVM does not hold any references to rcu protected data when it
 	 * switches CPU into a guest mode. In fact switching to a guest mode
@@ -699,7 +699,7 @@
 
 static inline void kvm_guest_exit(void)
 {
-	account_system_vtime(current);
+	vtime_account(current);
 	current->flags &= ~PF_VCPU;
 }