qspinlock.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _ASM_X86_QSPINLOCK_H
  3#define _ASM_X86_QSPINLOCK_H
  4
  5#include <linux/jump_label.h>
  6#include <asm/cpufeature.h>
  7#include <asm-generic/qspinlock_types.h>
  8#include <asm/paravirt.h>
  9#include <asm/rmwcc.h>
 10
 11#define _Q_PENDING_LOOPS	(1 << 9)
 12
 13#define queued_fetch_set_pending_acquire queued_fetch_set_pending_acquire
 14static __always_inline u32 queued_fetch_set_pending_acquire(struct qspinlock *lock)
 15{
 16	u32 val;
 17
 18	/*
 19	 * We can't use GEN_BINARY_RMWcc() inside an if() stmt because asm goto
 20	 * and CONFIG_PROFILE_ALL_BRANCHES=y results in a label inside a
 21	 * statement expression, which GCC doesn't like.
 22	 */
 23	val = GEN_BINARY_RMWcc(LOCK_PREFIX "btsl", lock->val.counter, c,
 24			       "I", _Q_PENDING_OFFSET) * _Q_PENDING_VAL;
 25	val |= atomic_read(&lock->val) & ~_Q_PENDING_MASK;
 26
 27	return val;
 28}
 29
 30#ifdef CONFIG_PARAVIRT_SPINLOCKS
 31extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
 32extern void __pv_init_lock_hash(void);
 33extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
 34extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock);
 35extern bool nopvspin;
 36
 37#define	queued_spin_unlock queued_spin_unlock
 38/**
 39 * queued_spin_unlock - release a queued spinlock
 40 * @lock : Pointer to queued spinlock structure
 41 *
 42 * A smp_store_release() on the least-significant byte.
 43 */
 44static inline void native_queued_spin_unlock(struct qspinlock *lock)
 45{
 46	smp_store_release(&lock->locked, 0);
 47}
 48
 49static inline void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
 50{
 51	pv_queued_spin_lock_slowpath(lock, val);
 52}
 53
 54static inline void queued_spin_unlock(struct qspinlock *lock)
 55{
 56	kcsan_release();
 57	pv_queued_spin_unlock(lock);
 58}
 59
 60#define vcpu_is_preempted vcpu_is_preempted
 61static inline bool vcpu_is_preempted(long cpu)
 62{
 63	return pv_vcpu_is_preempted(cpu);
 64}
 65#endif
 66
 67#ifdef CONFIG_PARAVIRT
 68/*
 69 * virt_spin_lock_key - disables by default the virt_spin_lock() hijack.
 70 *
 71 * Native (and PV wanting native due to vCPU pinning) should keep this key
 72 * disabled. Native does not touch the key.
 73 *
 74 * When in a guest then native_pv_lock_init() enables the key first and
 75 * KVM/XEN might conditionally disable it later in the boot process again.
 76 */
 77DECLARE_STATIC_KEY_FALSE(virt_spin_lock_key);
 78
 79/*
 80 * Shortcut for the queued_spin_lock_slowpath() function that allows
 81 * virt to hijack it.
 82 *
 83 * Returns:
 84 *   true - lock has been negotiated, all done;
 85 *   false - queued_spin_lock_slowpath() will do its thing.
 86 */
 87#define virt_spin_lock virt_spin_lock
 88static inline bool virt_spin_lock(struct qspinlock *lock)
 89{
 90	int val;
 91
 92	if (!static_branch_likely(&virt_spin_lock_key))
 93		return false;
 94
 95	/*
 96	 * On hypervisors without PARAVIRT_SPINLOCKS support we fall
 97	 * back to a Test-and-Set spinlock, because fair locks have
 98	 * horrible lock 'holder' preemption issues.
 99	 */
100
101 __retry:
102	val = atomic_read(&lock->val);
103
104	if (val || !atomic_try_cmpxchg(&lock->val, &val, _Q_LOCKED_VAL)) {
105		cpu_relax();
106		goto __retry;
107	}
108
109	return true;
110}
111
112#endif /* CONFIG_PARAVIRT */
113
114#include <asm-generic/qspinlock.h>
115
116#endif /* _ASM_X86_QSPINLOCK_H */