tools/virtio/ringtest: tweaks for s390

Make ringtest work on s390 too.

Signed-off-by: Halil Pasic <[e-mail]>
Acked-by: Sascha Silbe <[e-mail]>
Signed-off-by: Cornelia Huck <[e-mail]>

tools/virtio/ringtest/main.h

···
 #define VMEXIT_CYCLES 500
 #define VMENTRY_CYCLES 500
 
+#elif defined(__s390x__)
+static inline void wait_cycles(unsigned long long cycles)
+{
+	asm volatile("0: brctg %0,0b" : : "d" (cycles));
+}
+
+/* tweak me */
+#define VMEXIT_CYCLES 200
+#define VMENTRY_CYCLES 200
+
 #else
 static inline void wait_cycles(unsigned long long cycles)
 {
···
 /* Is there a portable way to do this? */
 #if defined(__x86_64__) || defined(__i386__)
 #define cpu_relax() asm ("rep; nop" ::: "memory")
+#elif defined(__s390x__)
+#define cpu_relax() barrier()
 #else
 #define cpu_relax() assert(0)
 #endif