1 | /* |
2 | * Copyright (C) 2018, Emilio G. Cota <cota@braap.org> |
3 | * |
4 | * License: GNU GPL, version 2 or later. |
5 | * See the COPYING file in the top-level directory. |
6 | */ |
7 | #include "qemu/osdep.h" |
8 | #include "qemu/atomic.h" |
9 | #include "qemu/thread.h" |
10 | |
11 | #ifdef CONFIG_ATOMIC64 |
12 | #error This file must only be compiled if !CONFIG_ATOMIC64 |
13 | #endif |
14 | |
15 | /* |
16 | * When !CONFIG_ATOMIC64, we serialize both reads and writes with spinlocks. |
17 | * We use an array of spinlocks, with padding computed at run-time based on |
18 | * the host's dcache line size. |
19 | * We point to the array with a void * to simplify the padding's computation. |
20 | * Each spinlock is located every lock_size bytes. |
21 | */ |
22 | static void *lock_array; |
23 | static size_t lock_size; |
24 | |
25 | /* |
26 | * Systems without CONFIG_ATOMIC64 are unlikely to have many cores, so we use a |
27 | * small array of locks. |
28 | */ |
29 | #define NR_LOCKS 16 |
30 | |
31 | static QemuSpin *addr_to_lock(const void *addr) |
32 | { |
33 | uintptr_t a = (uintptr_t)addr; |
34 | uintptr_t idx; |
35 | |
36 | idx = a >> qemu_dcache_linesize_log; |
37 | idx ^= (idx >> 8) ^ (idx >> 16); |
38 | idx &= NR_LOCKS - 1; |
39 | return lock_array + idx * lock_size; |
40 | } |
41 | |
42 | #define GEN_READ(name, type) \ |
43 | type name(const type *ptr) \ |
44 | { \ |
45 | QemuSpin *lock = addr_to_lock(ptr); \ |
46 | type ret; \ |
47 | \ |
48 | qemu_spin_lock(lock); \ |
49 | ret = *ptr; \ |
50 | qemu_spin_unlock(lock); \ |
51 | return ret; \ |
52 | } |
53 | |
54 | GEN_READ(atomic_read_i64, int64_t) |
55 | GEN_READ(atomic_read_u64, uint64_t) |
56 | #undef GEN_READ |
57 | |
58 | #define GEN_SET(name, type) \ |
59 | void name(type *ptr, type val) \ |
60 | { \ |
61 | QemuSpin *lock = addr_to_lock(ptr); \ |
62 | \ |
63 | qemu_spin_lock(lock); \ |
64 | *ptr = val; \ |
65 | qemu_spin_unlock(lock); \ |
66 | } |
67 | |
68 | GEN_SET(atomic_set_i64, int64_t) |
69 | GEN_SET(atomic_set_u64, uint64_t) |
70 | #undef GEN_SET |
71 | |
72 | void atomic64_init(void) |
73 | { |
74 | int i; |
75 | |
76 | lock_size = ROUND_UP(sizeof(QemuSpin), qemu_dcache_linesize); |
77 | lock_array = qemu_memalign(qemu_dcache_linesize, lock_size * NR_LOCKS); |
78 | for (i = 0; i < NR_LOCKS; i++) { |
79 | QemuSpin *lock = lock_array + i * lock_size; |
80 | |
81 | qemu_spin_init(lock); |
82 | } |
83 | } |
84 | |