linux-kernel - [PATCH 2/2] x86/cpufeatures: Enumerate MOVDIR64B instruction

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Date:   Wed, 24 Oct 2018 14:57:17 -0700
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     "Thomas Gleixner" <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...hat.com>, "H Peter Anvin" <hpa@...or.com>,
        "Ravi V Shankar" <ravi.v.shankar@...el.com>,
        "Ashok Raj" <ashok.raj@...el.com>
Cc:     "linux-kernel" <linux-kernel@...r.kernel.org>,
        "Fenghua Yu" <fenghua.yu@...el.com>
Subject: [PATCH 2/2] x86/cpufeatures: Enumerate MOVDIR64B instruction

MOVDIR64B moves 64-bytes as direct-store with 64-bytes write atomicity.
Direct store is implemented by using write combining (WC) for writing
data directly into memory without caching the data.

In low latency offload (e.g. Non-Volatile Memory, etc), MOVDIR64B writes
work descriptors (and data in some cases) to device-hosted work-queues
atomically without cache pollution.

Availability of the MOVDIR64B instruction is indicated by the
presence of the CPUID feature flag MOVDIR64B (CPUID.0x07.0x0:ECX[bit 28]).

Please check the latest Intel Architecture Instruction Set Extensions
and Future Features Programming Reference for more details on the CPUID
feature MOVDIR64B flag.

Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
---
 arch/x86/include/asm/cpufeatures.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 90934ee7b79a..28c4a502b419 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -332,6 +332,7 @@
 #define X86_FEATURE_RDPID		(16*32+22) /* RDPID instruction */
 #define X86_FEATURE_CLDEMOTE		(16*32+25) /* CLDEMOTE instruction */
 #define X86_FEATURE_MOVDIRI		(16*32+27) /* MOVDIRI instruction */
+#define X86_FEATURE_MOVDIR64B		(16*32+28) /* MOVDIR64B instruction */

 /* AMD-defined CPU features, CPUID level 0x80000007 (EBX), word 17 */
 #define X86_FEATURE_OVERFLOW_RECOV	(17*32+ 0) /* MCA overflow recovery support */
-- 
2.5.0