linux-kernel - [RFC PATCH 2/3] x86/cpufeatures: Add enumeration for SERIALIZE instruction

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Message-Id: <20200610200701.16757-3-kyung.min.park@intel.com>
Date:   Wed, 10 Jun 2020 13:07:00 -0700
From:   Kyung Min Park <kyung.min.park@...el.com>
To:     x86@...nel.org, linux-kernel@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        gregkh@...uxfoundation.org, ak@...ux.intel.com,
        dave.hansen@...el.com, tony.luck@...el.com,
        ravi.v.shankar@...el.com, ricardo.neri@...el.com,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject: [RFC PATCH 2/3] x86/cpufeatures: Add enumeration for SERIALIZE instruction

From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>

This instruction gives software a way to force the processor to complete
all modifications to flags, registers and memory from previous instructions
and drain all buffered writes to memory before the next instruction is
fetched and executed.

The same effect can be obtained using the cpuid instruction. However,
cpuid causes modification on the eax, ebx, ecx, and ecx regiters; it
also causes a VM exit.

A processor supports SERIALIZE instruction if CPUID.0x0x.0x0:EDX[14] is
present. The CPU feature flag is shown as "serialize" in /proc/cpuinfo.

Detailed information on the instructions and CPUID feature flag SERIALIZE
can be found in the latest Intel Architecture Instruction Set Extensions
and Future Features Programming Reference and Intel 64 and IA-32
Architectures Software Developer's Manual.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.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 db189945e9b0..cd9b1ec022ec 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -364,6 +364,7 @@
 #define X86_FEATURE_AVX512_VP2INTERSECT (18*32+ 8) /* AVX-512 Intersect for D/Q */
 #define X86_FEATURE_MD_CLEAR		(18*32+10) /* VERW clears CPU buffers */
 #define X86_FEATURE_TSX_FORCE_ABORT	(18*32+13) /* "" TSX_FORCE_ABORT */
+#define X86_FEATURE_SERIALIZE		(18*32+14) /* SERIALIZE instruction */
 #define X86_FEATURE_PCONFIG		(18*32+18) /* Intel PCONFIG */
 #define X86_FEATURE_SPEC_CTRL		(18*32+26) /* "" Speculation Control (IBRS + IBPB) */
 #define X86_FEATURE_INTEL_STIBP		(18*32+27) /* "" Single Thread Indirect Branch Predictors */
-- 
2.17.1