[PATCH 06/11] selftests: Fix arm64 IO barriers to match kernel

[Jason Gunthorpe <jgg@nvidia.com>]

The tools/include readl/writel MMIO accessors on arm64 use
inner-shareable barriers (dmb ish) while the kernel uses
outer-shareable (dmb osh).  Fix them to match.

Add __io_bw() and __io_ar() definitions matching the kernel's
arch/arm64/include/asm/io.h, including the dummy control dependency
in __io_ar() that orders MMIO reads against all subsequent
instructions.

Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 tools/arch/arm64/include/asm/barrier.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/arch/arm64/include/asm/barrier.h b/tools/arch/arm64/include/asm/barrier.h
index abdc64fc3c70f0..3f7fcb2a27541e 100644
--- a/tools/arch/arm64/include/asm/barrier.h
+++ b/tools/arch/arm64/include/asm/barrier.h
@@ -28,6 +28,20 @@
 #define dma_rmb()	asm volatile("dmb oshld" ::: "memory")
 #define dma_wmb()	asm volatile("dmb oshst" ::: "memory")
 
+/* Match arch/arm64/include/asm/io.h: use osh barriers for device MMIO */
+#define __io_bw()	dma_wmb()
+#define __io_ar(v)							\
+({									\
+	unsigned long tmp;						\
+									\
+	dma_rmb();							\
+									\
+	asm volatile("eor	%0, %1, %1\n"				\
+		     "cbnz	%0, ."					\
+		     : "=r" (tmp) : "r" ((unsigned long)(v))		\
+		     : "memory");					\
+})
+
 #define smp_store_release(p, v)						\
 do {									\
 	union { typeof(*p) __val; char __c[1]; } __u =			\
-- 
2.43.0