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 #include "qemu/cacheinfo.h" 11 12 #ifdef CONFIG_ATOMIC64 13 #error This file must only be compiled if !CONFIG_ATOMIC64 14 #endif 15 16 /* 17 * When !CONFIG_ATOMIC64, we serialize both reads and writes with spinlocks. 18 * We use an array of spinlocks, with padding computed at run-time based on 19 * the host's dcache line size. 20 * We point to the array with a void * to simplify the padding's computation. 21 * Each spinlock is located every lock_size bytes. 22 */ 23 static void *lock_array; 24 static size_t lock_size; 25 26 /* 27 * Systems without CONFIG_ATOMIC64 are unlikely to have many cores, so we use a 28 * small array of locks. 29 */ 30 #define NR_LOCKS 16 31 32 static QemuSpin *addr_to_lock(const void *addr) 33 { 34 uintptr_t a = (uintptr_t)addr; 35 uintptr_t idx; 36 37 idx = a >> qemu_dcache_linesize_log; 38 idx ^= (idx >> 8) ^ (idx >> 16); 39 idx &= NR_LOCKS - 1; 40 return lock_array + idx * lock_size; 41 } 42 43 #define GEN_READ(name, type) \ 44 type name(const type *ptr) \ 45 { \ 46 QemuSpin *lock = addr_to_lock(ptr); \ 47 type ret; \ 48 \ 49 qemu_spin_lock(lock); \ 50 ret = *ptr; \ 51 qemu_spin_unlock(lock); \ 52 return ret; \ 53 } 54 55 GEN_READ(qatomic_read_i64, int64_t) 56 GEN_READ(qatomic_read_u64, uint64_t) 57 #undef GEN_READ 58 59 #define GEN_SET(name, type) \ 60 void name(type *ptr, type val) \ 61 { \ 62 QemuSpin *lock = addr_to_lock(ptr); \ 63 \ 64 qemu_spin_lock(lock); \ 65 *ptr = val; \ 66 qemu_spin_unlock(lock); \ 67 } 68 69 GEN_SET(qatomic_set_i64, int64_t) 70 GEN_SET(qatomic_set_u64, uint64_t) 71 #undef GEN_SET 72 73 void qatomic64_init(void) 74 { 75 int i; 76 77 lock_size = ROUND_UP(sizeof(QemuSpin), qemu_dcache_linesize); 78 lock_array = qemu_memalign(qemu_dcache_linesize, lock_size * NR_LOCKS); 79 for (i = 0; i < NR_LOCKS; i++) { 80 QemuSpin *lock = lock_array + i * lock_size; 81 82 qemu_spin_init(lock); 83 } 84 } 85