Emilio G. Cota | 782da5b | 2018-09-10 19:27:42 -0400 | [diff] [blame] | 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 | |
Stefan Hajnoczi | d73415a | 2020-09-23 11:56:46 +0100 | [diff] [blame] | 54 | GEN_READ(qatomic_read_i64, int64_t) |
| 55 | GEN_READ(qatomic_read_u64, uint64_t) |
Emilio G. Cota | 782da5b | 2018-09-10 19:27:42 -0400 | [diff] [blame] | 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 | |
Stefan Hajnoczi | d73415a | 2020-09-23 11:56:46 +0100 | [diff] [blame] | 68 | GEN_SET(qatomic_set_i64, int64_t) |
| 69 | GEN_SET(qatomic_set_u64, uint64_t) |
Emilio G. Cota | 782da5b | 2018-09-10 19:27:42 -0400 | [diff] [blame] | 70 | #undef GEN_SET |
| 71 | |
Stefan Hajnoczi | d73415a | 2020-09-23 11:56:46 +0100 | [diff] [blame] | 72 | void qatomic64_init(void) |
Emilio G. Cota | 782da5b | 2018-09-10 19:27:42 -0400 | [diff] [blame] | 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 | } |