tools/virtio: copy READ/WRITE_ONCE

This is to make ptr_ring test build again.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 57 insertions, 0 deletions

diff --git a/tools/virtio/ringtest/main.h b/tools/virtio/ringtest/main.h
index 5706e075adf2..593a3289c87d 100644
--- a/tools/virtio/ringtest/main.h
+++ b/tools/virtio/ringtest/main.h
@@ -134,4 +134,61 @@ static inline void busy_wait(void)
     barrier(); \
 } while (0)
 
+#if defined(__i386__) || defined(__x86_64__) || defined(__s390x__)
+#define smp_wmb() barrier()
+#else
+#define smp_wmb() smp_release()
+#endif
+
+#ifdef __alpha__
+#define smp_read_barrier_depends() smp_acquire()
+#else
+#define smp_read_barrier_depends() do {} while(0)
+#endif
+
+static __always_inline
+void __read_once_size(const volatile void *p, void *res, int size)
+{
+        switch (size) {                                                 \
+        case 1: *(unsigned char *)res = *(volatile unsigned char *)p; break;              \
+        case 2: *(unsigned short *)res = *(volatile unsigned short *)p; break;            \
+        case 4: *(unsigned int *)res = *(volatile unsigned int *)p; break;            \
+        case 8: *(unsigned long long *)res = *(volatile unsigned long long *)p; break;            \
+        default:                                                        \
+                barrier();                                              \
+                __builtin_memcpy((void *)res, (const void *)p, size);   \
+                barrier();                                              \
+        }                                                               \
+}
+
+static __always_inline void __write_once_size(volatile void *p, void *res, int size)
+{
+        switch (size) {
+        case 1: *(volatile unsigned char *)p = *(unsigned char *)res; break;
+        case 2: *(volatile unsigned short *)p = *(unsigned short *)res; break;
+        case 4: *(volatile unsigned int *)p = *(unsigned int *)res; break;
+        case 8: *(volatile unsigned long long *)p = *(unsigned long long *)res; break;
+        default:
+                barrier();
+                __builtin_memcpy((void *)p, (const void *)res, size);
+                barrier();
+        }
+}
+
+#define READ_ONCE(x) \
+({                                                                      \
+        union { typeof(x) __val; char __c[1]; } __u;                    \
+        __read_once_size(&(x), __u.__c, sizeof(x));             \
+        smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
+        __u.__val;                                                      \
+})
+
+#define WRITE_ONCE(x, val) \
+({                                                      \
+        union { typeof(x) __val; char __c[1]; } __u =   \
+                { .__val = (typeof(x)) (val) }; \
+        __write_once_size(&(x), __u.__c, sizeof(x));    \
+        __u.__val;                                      \
+})
+
 #endif