context_tracing: Fix guest accounting with native vtime

1) If context tracking is enabled with native vtime accounting (which
combo is useless except for dev testing), we call vtime_guest_enter()
and vtime_guest_exit() on host <-> guest switches. But those are stubs
in this configurations. As a result, cputime is not correctly flushed
on kvm context switches.

2) If context tracking runs but is disabled on some CPUs, those
CPUs end up calling __guest_enter/__guest_exit which in turn
call vtime_account_system(). We don't want to call this because we
run in tick based accounting for these CPUs.

Refactor the guest_enter/guest_exit code such that all combinations
finally work.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>

1 files changed, 22 insertions, 30 deletions

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index fc09d7b0dacf..5984f2556d13 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -20,25 +20,6 @@ struct context_tracking {
         } state;
 };
 
-static inline void __guest_enter(void)
-{
-        /*
-         * This is running in ioctl context so we can avoid
-         * the call to vtime_account() with its unnecessary idle check.
-         */
-        vtime_account_system(current);
-        current->flags |= PF_VCPU;
-}
-
-static inline void __guest_exit(void)
-{
-        /*
-         * This is running in ioctl context so we can avoid
-         * the call to vtime_account() with its unnecessary idle check.
-         */
-        vtime_account_system(current);
-        current->flags &= ~PF_VCPU;
-}
 
 #ifdef CONFIG_CONTEXT_TRACKING
 DECLARE_PER_CPU(struct context_tracking, context_tracking);
@@ -56,9 +37,6 @@ static inline bool context_tracking_active(void)
 extern void user_enter(void);
 extern void user_exit(void);
 
-extern void guest_enter(void);
-extern void guest_exit(void);
-
 static inline enum ctx_state exception_enter(void)
 {
         enum ctx_state prev_ctx;
@@ -81,21 +59,35 @@ extern void context_tracking_task_switch(struct task_struct *prev,
 static inline bool context_tracking_in_user(void) { return false; }
 static inline void user_enter(void) { }
 static inline void user_exit(void) { }
+static inline enum ctx_state exception_enter(void) { return 0; }
+static inline void exception_exit(enum ctx_state prev_ctx) { }
+static inline void context_tracking_task_switch(struct task_struct *prev,
+                                                struct task_struct *next) { }
+#endif /* !CONFIG_CONTEXT_TRACKING */
 
+#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
+extern void guest_enter(void);
+extern void guest_exit(void);
+#else
 static inline void guest_enter(void)
 {
-        __guest_enter();
+        /*
+         * This is running in ioctl context so we can avoid
+         * the call to vtime_account() with its unnecessary idle check.
+         */
+        vtime_account_system(current);
+        current->flags |= PF_VCPU;
 }
 
 static inline void guest_exit(void)
 {
-        __guest_exit();
+        /*
+         * This is running in ioctl context so we can avoid
+         * the call to vtime_account() with its unnecessary idle check.
+         */
+        vtime_account_system(current);
+        current->flags &= ~PF_VCPU;
 }
-
-static inline enum ctx_state exception_enter(void) { return 0; }
-static inline void exception_exit(enum ctx_state prev_ctx) { }
-static inline void context_tracking_task_switch(struct task_struct *prev,
-                                                struct task_struct *next) { }
-#endif /* !CONFIG_CONTEXT_TRACKING */
+#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */
 
 #endif