tools headers: Import iosubmit_cmds512()

Import iosubmit_cmds512() from arch/x86/include/asm/io.h into tools/ so
it can be used by VFIO selftests to interact with Intel DSA devices.

Also pull in movdir64b() from arch/x86/include/asm/special_insns.h into
tools/, which is the underlying instruction used by iosubmit_cmds512().

Changes made when importing: None

Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20250822212518.4156428-21-dmatlack@google.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

2 files changed, 53 insertions, 0 deletions

diff --git a/tools/arch/x86/include/asm/io.h b/tools/arch/x86/include/asm/io.h
index 4c787a2363de..ecad61a3ea52 100644
--- a/tools/arch/x86/include/asm/io.h
+++ b/tools/arch/x86/include/asm/io.h
@@ -4,6 +4,7 @@
 
 #include <linux/compiler.h>
 #include <linux/types.h>
+#include "special_insns.h"
 
 #define build_mmio_read(name, size, type, reg, barrier) \
 static inline type name(const volatile void __iomem *addr) \
@@ -72,4 +73,29 @@ build_mmio_write(__writeq, "q", u64, "r", )
 
 #include <asm-generic/io.h>
 
+/**
+ * iosubmit_cmds512 - copy data to single MMIO location, in 512-bit units
+ * @dst: destination, in MMIO space (must be 512-bit aligned)
+ * @src: source
+ * @count: number of 512 bits quantities to submit
+ *
+ * Submit data from kernel space to MMIO space, in units of 512 bits at a
+ * time.  Order of access is not guaranteed, nor is a memory barrier
+ * performed afterwards.
+ *
+ * Warning: Do not use this helper unless your driver has checked that the CPU
+ * instruction is supported on the platform.
+ */
+static inline void iosubmit_cmds512(void __iomem *dst, const void *src,
+				    size_t count)
+{
+	const u8 *from = src;
+	const u8 *end = from + count * 64;
+
+	while (from < end) {
+		movdir64b(dst, from);
+		from += 64;
+	}
+}
+
 #endif /* _TOOLS_ASM_X86_IO_H */
diff --git a/tools/arch/x86/include/asm/special_insns.h b/tools/arch/x86/include/asm/special_insns.h
new file mode 100644
index 000000000000..04af42a99c38
--- /dev/null
+++ b/tools/arch/x86/include/asm/special_insns.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _TOOLS_ASM_X86_SPECIAL_INSNS_H
+#define _TOOLS_ASM_X86_SPECIAL_INSNS_H
+
+/* The dst parameter must be 64-bytes aligned */
+static inline void movdir64b(void *dst, const void *src)
+{
+	const struct { char _[64]; } *__src = src;
+	struct { char _[64]; } *__dst = dst;
+
+	/*
+	 * MOVDIR64B %(rdx), rax.
+	 *
+	 * Both __src and __dst must be memory constraints in order to tell the
+	 * compiler that no other memory accesses should be reordered around
+	 * this one.
+	 *
+	 * Also, both must be supplied as lvalues because this tells
+	 * the compiler what the object is (its size) the instruction accesses.
+	 * I.e., not the pointers but what they point to, thus the deref'ing '*'.
+	 */
+	asm volatile(".byte 0x66, 0x0f, 0x38, 0xf8, 0x02"
+		     : "+m" (*__dst)
+		     :  "m" (*__src), "a" (__dst), "d" (__src));
+}
+
+#endif /* _TOOLS_ASM_X86_SPECIAL_INSNS_H */