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
14 static __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
31 extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
32 extern void __pv_init_lock_hash(void);
33 extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
34 extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock);
35 extern 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 */
44 static inline void native_queued_spin_unlock(struct qspinlock *lock)
45 {
46 smp_store_release(&lock->locked, 0);
47 }
48
49 static inline void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
50 {
51 pv_queued_spin_lock_slowpath(lock, val);
52 }
53
54 static 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
61 static 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 */
77 DECLARE_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
88 static 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 */
117
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