Greg Kroah-Hartman
598cf27219
Link: https://lore.kernel.org/r/20260217200002.683975158@linuxfoundation.org Tested-by: Florian Fainelli <florian.fainelli@broadcom.com> Tested-by: Takeshi Ogasawara <takeshi.ogasawara@futuring-girl.com> Tested-by: Peter Schneider <pschneider1968@googlemail.com> Tested-by: Jon Hunter <jonathanh@nvidia.com> Tested-by: Salvatore Bonaccorso <carnil@debian.org> Tested-by: Brett A C Sheffield <bacs@librecast.net> Tested-by: Mark Brown <broonie@kernel.org> Tested-by: Luna Jernberg <droidbittin@gmail.com> Tested-by: Ronald Warsow <rwarsow@gmx.de> Tested-by: Justin M. Forbes <jforbes@fedoraproject.org> Tested-by: Ron Economos <re@w6rz.net> Tested-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
120 lines
3.0 KiB
C
120 lines
3.0 KiB
C
/* SPDX-License-Identifier: MIT */
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/*
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* Copyright © 2025 Intel Corporation
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*/
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#ifndef _XE_GUARD_H_
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#define _XE_GUARD_H_
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#include <linux/spinlock.h>
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/**
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* struct xe_guard - Simple logic to protect a feature.
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*
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* Implements simple semaphore-like logic that can be used to lockdown the
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* feature unless it is already in use. Allows enabling of the otherwise
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* incompatible features, where we can't follow the strict owner semantics
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* required by the &rw_semaphore.
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*
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* NOTE! It shouldn't be used to protect a data, use &rw_semaphore instead.
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*/
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struct xe_guard {
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/**
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* @counter: implements simple exclusive/lockdown logic:
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* if == 0 then guard/feature is idle/not in use,
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* if < 0 then feature is active and can't be locked-down,
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* if > 0 then feature is lockded-down and can't be activated.
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*/
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int counter;
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/** @name: the name of the guard (useful for debug) */
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const char *name;
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/** @owner: the info about the last owner of the guard (for debug) */
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void *owner;
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/** @lock: protects guard's data */
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spinlock_t lock;
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};
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/**
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* xe_guard_init() - Initialize the guard.
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* @guard: the &xe_guard to init
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* @name: name of the guard
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*/
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static inline void xe_guard_init(struct xe_guard *guard, const char *name)
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{
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spin_lock_init(&guard->lock);
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guard->counter = 0;
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guard->name = name;
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}
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/**
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* xe_guard_arm() - Arm the guard for the exclusive/lockdown mode.
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* @guard: the &xe_guard to arm
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* @lockdown: arm for lockdown(true) or exclusive(false) mode
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* @who: optional owner info (for debug only)
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*
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* Multiple lockdown requests are allowed.
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* Only single exclusive access can be granted.
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* Will fail if the guard is already in exclusive mode.
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* On success, must call the xe_guard_disarm() to release.
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*
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* Return: 0 on success or a negative error code on failure.
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*/
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static inline int xe_guard_arm(struct xe_guard *guard, bool lockdown, void *who)
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{
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guard(spinlock)(&guard->lock);
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if (lockdown) {
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if (guard->counter < 0)
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return -EBUSY;
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guard->counter++;
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} else {
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if (guard->counter > 0)
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return -EPERM;
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if (guard->counter < 0)
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return -EUSERS;
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guard->counter--;
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}
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guard->owner = who;
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return 0;
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}
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/**
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* xe_guard_disarm() - Disarm the guard from exclusive/lockdown mode.
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* @guard: the &xe_guard to disarm
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* @lockdown: disarm from lockdown(true) or exclusive(false) mode
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*
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* Return: true if successfully disarmed or false in case of mismatch.
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*/
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static inline bool xe_guard_disarm(struct xe_guard *guard, bool lockdown)
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{
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guard(spinlock)(&guard->lock);
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if (lockdown) {
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if (guard->counter <= 0)
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return false;
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guard->counter--;
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} else {
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if (guard->counter != -1)
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return false;
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guard->counter++;
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}
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return true;
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}
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/**
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* xe_guard_mode_str() - Convert guard mode into a string.
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* @lockdown: flag used to select lockdown or exclusive mode
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*
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* Return: "lockdown" or "exclusive" string.
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*/
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static inline const char *xe_guard_mode_str(bool lockdown)
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{
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return lockdown ? "lockdown" : "exclusive";
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}
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#endif
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