At the moment, xchg on sh only supports 4 and 1 byte values, so using it
from smp_store_mb means attempts to store a 2 byte value using this
macro fail.
And happens to be exactly what virtio drivers want to do.
Check size and fall back to a slower, but safe, WRITE_ONCE+smp_mb.
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
arch/sh/include/asm/barrier.h | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/sh/include/asm/barrier.h b/arch/sh/include/asm/barrier.h
index f887c64..0cc5735 100644
--- a/arch/sh/include/asm/barrier.h
+++ b/arch/sh/include/asm/barrier.h
@@ -32,7 +32,15 @@
#define ctrl_barrier() __asm__ __volatile__ ("nop;nop;nop;nop;nop;nop;nop;nop")
#endif
-#define __smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0)
+#define __smp_store_mb(var, value) do { \
+ if (sizeof(var) != 4 && sizeof(var) != 1) { \
+ WRITE_ONCE(var, value); \
+ __smp_mb(); \
+ } else { \
+ (void)xchg(&var, value); \
+ } \
+} while (0)
+
#define smp_store_mb(var, value) __smp_store_mb(var, value)
#include <asm-generic/barrier.h>
--
MST
_______________________________________________
Virtualization mailing list
Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
