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author | 2023-10-10 11:40:56 +0000 | |
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committer | 2023-10-10 11:40:56 +0000 | |
commit | e02cda008591317b1625707ff8e115a4841aa889 (patch) | |
tree | aee302e3cf8b59ec2d32ec481be3d1afddfc8968 /util/atomic64.c | |
parent | cc668e6b7e0ffd8c9d130513d12053cf5eda1d3b (diff) |
Introduce Virtio-loopback epsilon release:
Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.
Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9
Diffstat (limited to 'util/atomic64.c')
-rw-r--r-- | util/atomic64.c | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/util/atomic64.c b/util/atomic64.c new file mode 100644 index 000000000..93037d5b1 --- /dev/null +++ b/util/atomic64.c @@ -0,0 +1,83 @@ +/* + * Copyright (C) 2018, Emilio G. Cota <cota@braap.org> + * + * License: GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ +#include "qemu/osdep.h" +#include "qemu/atomic.h" +#include "qemu/thread.h" + +#ifdef CONFIG_ATOMIC64 +#error This file must only be compiled if !CONFIG_ATOMIC64 +#endif + +/* + * When !CONFIG_ATOMIC64, we serialize both reads and writes with spinlocks. + * We use an array of spinlocks, with padding computed at run-time based on + * the host's dcache line size. + * We point to the array with a void * to simplify the padding's computation. + * Each spinlock is located every lock_size bytes. + */ +static void *lock_array; +static size_t lock_size; + +/* + * Systems without CONFIG_ATOMIC64 are unlikely to have many cores, so we use a + * small array of locks. + */ +#define NR_LOCKS 16 + +static QemuSpin *addr_to_lock(const void *addr) +{ + uintptr_t a = (uintptr_t)addr; + uintptr_t idx; + + idx = a >> qemu_dcache_linesize_log; + idx ^= (idx >> 8) ^ (idx >> 16); + idx &= NR_LOCKS - 1; + return lock_array + idx * lock_size; +} + +#define GEN_READ(name, type) \ + type name(const type *ptr) \ + { \ + QemuSpin *lock = addr_to_lock(ptr); \ + type ret; \ + \ + qemu_spin_lock(lock); \ + ret = *ptr; \ + qemu_spin_unlock(lock); \ + return ret; \ + } + +GEN_READ(qatomic_read_i64, int64_t) +GEN_READ(qatomic_read_u64, uint64_t) +#undef GEN_READ + +#define GEN_SET(name, type) \ + void name(type *ptr, type val) \ + { \ + QemuSpin *lock = addr_to_lock(ptr); \ + \ + qemu_spin_lock(lock); \ + *ptr = val; \ + qemu_spin_unlock(lock); \ + } + +GEN_SET(qatomic_set_i64, int64_t) +GEN_SET(qatomic_set_u64, uint64_t) +#undef GEN_SET + +void qatomic64_init(void) +{ + int i; + + lock_size = ROUND_UP(sizeof(QemuSpin), qemu_dcache_linesize); + lock_array = qemu_memalign(qemu_dcache_linesize, lock_size * NR_LOCKS); + for (i = 0; i < NR_LOCKS; i++) { + QemuSpin *lock = lock_array + i * lock_size; + + qemu_spin_init(lock); + } +} |