Commit 2d854e57 authored by Frederic Weisbecker's avatar Frederic Weisbecker
Browse files

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: default avatarFrederic 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>
parent fbb00b56

include/linux/context_tracking.h

+22 −30
Original line number Diff line number Diff line
@@ -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

kernel/context_tracking.c

+4 −2
Original line number Diff line number Diff line
@@ -141,12 +141,13 @@ void user_exit(void) 
	local_irq_restore(flags);

}



#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN

void guest_enter(void)

{

	if (vtime_accounting_enabled())

		vtime_guest_enter(current);

	else

		__guest_enter();

		current->flags |= PF_VCPU;

}

EXPORT_SYMBOL_GPL(guest_enter);
@@ -155,9 +156,10 @@ void guest_exit(void) 
	if (vtime_accounting_enabled())

		vtime_guest_exit(current);

	else

		__guest_exit();

		current->flags &= ~PF_VCPU;

}

EXPORT_SYMBOL_GPL(guest_exit);

#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */





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