virtio/asm/barrier.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 #include <stdlib.h>
0003 #if defined(__i386__) || defined(__x86_64__)
0004 #define barrier() asm volatile("" ::: "memory")
0005 #define virt_mb() __sync_synchronize()
0006 #define virt_rmb() barrier()
0007 #define virt_wmb() barrier()
0008 /* Atomic store should be enough, but gcc generates worse code in that case. */
0009 #define virt_store_mb(var, value)  do { \
0010     typeof(var) virt_store_mb_value = (value); \
0011     __atomic_exchange(&(var), &virt_store_mb_value, &virt_store_mb_value, \
0012               __ATOMIC_SEQ_CST); \
0013     barrier(); \
0014 } while (0);
0015 /* Weak barriers should be used. If not - it's a bug */
0016 # define mb() abort()
0017 # define dma_rmb() abort()
0018 # define dma_wmb() abort()
0019 #elif defined(__aarch64__)
0020 #define dmb(opt) asm volatile("dmb " #opt : : : "memory")
0021 #define virt_mb() __sync_synchronize()
0022 #define virt_rmb() dmb(ishld)
0023 #define virt_wmb() dmb(ishst)
0024 #define virt_store_mb(var, value)  do { WRITE_ONCE(var, value); dmb(ish); } while (0)
0025 /* Weak barriers should be used. If not - it's a bug */
0026 # define mb() abort()
0027 # define dma_rmb() abort()
0028 # define dma_wmb() abort()
0029 #else
0030 #error Please fill in barrier macros
0031 #endif
0032