[PATCH 05/11] selftests: Add additional kernel functions to tools/include/

Jason Gunthorpe
2026-05-01T00:08:41Z

These are needed by the VFIO mlx5 selftest in the following patches,
which includes some headers from mlx5 and also needs a few more
MMIO-related features.

- DECLARE_FLEX_ARRAY in new tools/include/linux/stddef.h (wraps
existing __DECLARE_FLEX_ARRAY from uapi/linux/stddef.h)

- dma_wmb/dma_rmb barriers: x86 uses compiler barrier
(DMA-coherent), arm64 uses dmb oshst/oshld (outer-shareable for
device visibility), generic fallback uses wmb/rmb

- ioread32be/iowrite32be in tools/include/asm-generic/io.h for
big-endian MMIO register access

Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
tools/arch/arm64/include/asm/barrier.h | 4 ++++
tools/arch/x86/include/asm/barrier.h | 5 +++++
tools/include/asm-generic/io.h | 28 ++++++++++++++++++++++++++
tools/include/asm/barrier.h | 8 ++++++++
tools/include/linux/stddef.h | 10 +++++++++
5 files changed, 55 insertions(+)
create mode 100644 tools/include/linux/stddef.h

diff --git a/tools/arch/arm64/include/asm/barrier.h b/tools/arch/arm64/include/asm/barrier.h
index 3b9b41331c4f16..abdc64fc3c70f0 100644
--- a/tools/arch/arm64/include/asm/barrier.h
+++ b/tools/arch/arm64/include/asm/barrier.h
@@ -24,6 +24,10 @@
#define smp_wmb() asm volatile("dmb ishst" ::: "memory")
#define smp_rmb() asm volatile("dmb ishld" ::: "memory")

+/* DMA barriers use outer-shareable (osh) for device visibility */
+#define dma_rmb() asm volatile("dmb oshld" ::: "memory")
+#define dma_wmb() asm volatile("dmb oshst" ::: "memory")
+
#define smp_store_release(p, v) \
do { \
union { typeof(*p) __val; char __c[1]; } __u = \
diff --git a/tools/arch/x86/include/asm/barrier.h b/tools/arch/x86/include/asm/barrier.h
index 0adf295dd5b6aa..0b51431fa530ea 100644
--- a/tools/arch/x86/include/asm/barrier.h
+++ b/tools/arch/x86/include/asm/barrier.h
@@ -43,4 +43,9 @@ do { \
___p1; \
})
#endif /* defined(__x86_64__) */
+
+/* x86 is DMA-coherent so DMA barriers are just compiler barriers */
+#define dma_rmb() barrier()
+#define dma_wmb() barrier()
+
#endif /* _TOOLS_LINUX_ASM_X86_BARRIER_H */
diff --git a/tools/include/asm-generic/io.h b/tools/include/asm-generic/io.h
index e5a0b07ad452a6..0d89decdafb818 100644
--- a/tools/include/asm-generic/io.h
+++ b/tools/include/asm-generic/io.h
@@ -479,4 +479,32 @@ static inline void writesq(volatile void __iomem *addr, const void *buffer,
}
#endif

+/*
+ * ioread/iowrite for big-endian MMIO registers.
+ */
+
+#ifndef ioread32be
+#define ioread32be ioread32be
+static inline u32 ioread32be(const volatile void __iomem *addr)
+{
+ return bswap_32(readl(addr));
+}
+#endif
+
+#ifndef iowrite32be
+#define iowrite32be iowrite32be
+static inline void iowrite32be(u32 value, volatile void __iomem *addr)
+{
+ writel(bswap_32(value), addr);
+}
+#endif
+
+#ifndef iowrite64be
+#define iowrite64be iowrite64be
+static inline void iowrite64be(u64 value, volatile void __iomem *addr)
+{
+ writeq(bswap_64(value), addr);
+}
+#endif
+
#endif /* _TOOLS_ASM_GENERIC_IO_H */
diff --git a/tools/include/asm/barrier.h b/tools/include/asm/barrier.h
index 0c21678ac5e65f..e7e0c7de5a2ffe 100644
--- a/tools/include/asm/barrier.h
+++ b/tools/include/asm/barrier.h
@@ -47,6 +47,14 @@
# define smp_mb() mb()
#endif

+#ifndef dma_rmb
+# define dma_rmb() rmb()
+#endif
+
+#ifndef dma_wmb
+# define dma_wmb() wmb()
+#endif
+
#ifndef smp_store_release
# define smp_store_release(p, v) \
do { \
diff --git a/tools/include/linux/stddef.h b/tools/include/linux/stddef.h
new file mode 100644
index 00000000000000..99182ea4a1419b
--- /dev/null
+++ b/tools/include/linux/stddef.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _TOOLS_LINUX_STDDEF_H
+#define _TOOLS_LINUX_STDDEF_H
+
+#include_next <linux/stddef.h>
+
+#define DECLARE_FLEX_ARRAY(TYPE, NAME) \
+ __DECLARE_FLEX_ARRAY(TYPE, NAME)
+
+#endif /* _TOOLS_LINUX_STDDEF_H */
--
2.43.0