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https://github.com/torvalds/linux.git
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Frederic Weisbecker
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 <[email protected]> Signed-off-by: Frederic Weisbecker <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Jacek Anaszewski <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Pavel Machek <[email protected]> Cc: Rafael J . Wysocki <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Viresh Kumar <[email protected]> Cc: Wanpeng Li <[email protected]> Cc: Yauheni Kaliuta <[email protected]> Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]>
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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