xen/riscv: introduces acquire, release and full barriers

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/riscv/include/asm/fence.h

@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _ASM_RISCV_FENCE_H
+#define _ASM_RISCV_FENCE_H
+
+#define RISCV_ACQUIRE_BARRIER   "\tfence r , rw\n"
+#define RISCV_RELEASE_BARRIER   "\tfence rw, w\n"
+#define RISCV_FULL_BARRIER      "\tfence rw, rw\n"
+
+#endif	/* _ASM_RISCV_FENCE_H */