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023e9deb51
guest_enter() doesn't call context_tracking_enabled() before calling context_tracking_enabled_this_cpu(). Therefore the guest code doesn't benefit from the static key on the fast path. Just make sure that context_tracking_enabled_*cpu() functions check the static key by themselves to propagate the optimization. Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Pavel Machek <pavel@ucw.cz> Cc: Rafael J . Wysocki <rjw@rjwysocki.net> Cc: Rik van Riel <riel@surriel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: Wanpeng Li <wanpengli@tencent.com> Cc: Yauheni Kaliuta <yauheni.kaliuta@redhat.com> Link: https://lkml.kernel.org/r/20191016025700.31277-11-frederic@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
56 lines
1.6 KiB
C
56 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_CONTEXT_TRACKING_STATE_H
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#define _LINUX_CONTEXT_TRACKING_STATE_H
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#include <linux/percpu.h>
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#include <linux/static_key.h>
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struct context_tracking {
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/*
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* When active is false, probes are unset in order
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* to minimize overhead: TIF flags are cleared
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* and calls to user_enter/exit are ignored. This
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* may be further optimized using static keys.
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*/
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bool active;
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int recursion;
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enum ctx_state {
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CONTEXT_DISABLED = -1, /* returned by ct_state() if unknown */
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CONTEXT_KERNEL = 0,
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CONTEXT_USER,
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CONTEXT_GUEST,
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} state;
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};
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#ifdef CONFIG_CONTEXT_TRACKING
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extern struct static_key_false context_tracking_key;
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DECLARE_PER_CPU(struct context_tracking, context_tracking);
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static inline bool context_tracking_enabled(void)
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{
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return static_branch_unlikely(&context_tracking_key);
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}
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static inline bool context_tracking_enabled_cpu(int cpu)
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{
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return context_tracking_enabled() && per_cpu(context_tracking.active, cpu);
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}
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static inline bool context_tracking_enabled_this_cpu(void)
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{
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return context_tracking_enabled() && __this_cpu_read(context_tracking.active);
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}
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static inline bool context_tracking_in_user(void)
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{
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return __this_cpu_read(context_tracking.state) == CONTEXT_USER;
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}
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#else
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static inline bool context_tracking_in_user(void) { return false; }
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static inline bool context_tracking_enabled(void) { return false; }
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static inline bool context_tracking_enabled_cpu(int cpu) { return false; }
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static inline bool context_tracking_enabled_this_cpu(void) { return false; }
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#endif /* CONFIG_CONTEXT_TRACKING */
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#endif
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