[PATCH] x86/asm: Add support for MOVDIR64B instruction

Kirill A. Shutemov
2019-07-30T23:06:00Z

Add support for a new instruction MOVDIR64B. The instruction moves
64-bytes as direct-store with 64-byte write atomicity from source memory
address to destination memory address.

MOVDIR64B requires the destination address to be 64-byte aligned. No
alignment restriction is enforced for source operand.

See Intel Software Developer’s Manual for more information on the
instruction.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---

Several upcoming patchsets will make use of the helper.

---
arch/x86/include/asm/special_insns.h | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
index 219be88a59d2..059e7bd331d2 100644
--- a/arch/x86/include/asm/special_insns.h
+++ b/arch/x86/include/asm/special_insns.h
@@ -248,6 +248,13 @@ static inline void clwb(volatile void *__p)

#define nop() asm volatile ("nop")

+static inline void movdir64b(void *dst, const void *src)
+{
+ /* movdir64b [rdx], rax */
+ asm volatile(".byte 0x66, 0x0f, 0x38, 0xf8, 0x02"
+ : "=m" (*(char *)dst)
+ : "d" (src), "a" (dst));
+}

#endif /* __KERNEL__ */

--
2.21.0