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

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Message-Id: <20190730230554.8291-1-kirill.shutemov@linux.intel.com>
Date:   Wed, 31 Jul 2019 02:05:54 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, "Luck, Tony" <tony.luck@...el.com>,
        "Lin, Jing" <jing.lin@...el.com>,
        "Kumar, Sanjay K" <sanjay.k.kumar@...el.com>,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH] x86/asm: Add support for MOVDIR64B instruction

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@...ux.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