linux-kernel - [tip:x86/cpufeature] x86/msr: Add MSR_MISC_FEATURE

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Message-ID: <tip-ae47eda905e61ef6ba0b6f79b967c9de15ca4f8e@git.kernel.org>
Date:   Sat, 4 Feb 2017 08:30:51 -0800
From:   tip-bot for Grzegorz Andrejczuk <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     grzegorz.andrejczuk@...el.com, mingo@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, hpa@...or.com
Subject: [tip:x86/cpufeature] x86/msr: Add MSR_MISC_FEATURE_ENABLES and
 RING3MWAIT bit

Commit-ID:  ae47eda905e61ef6ba0b6f79b967c9de15ca4f8e
Gitweb:     http://git.kernel.org/tip/ae47eda905e61ef6ba0b6f79b967c9de15ca4f8e
Author:     Grzegorz Andrejczuk <grzegorz.andrejczuk@...el.com>
AuthorDate: Fri, 20 Jan 2017 14:22:33 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Sat, 4 Feb 2017 08:51:09 +0100

x86/msr: Add MSR_MISC_FEATURE_ENABLES and RING3MWAIT bit

Define new MSR MISC_FEATURE_ENABLES (0x140).

On supported CPUs if bit 1 of this MSR is set, then calling MONITOR and
MWAIT instructions outside of ring 0 will not cause invalid-opcode
exception.

The MSR MISC_FEATURE_ENABLES is not yet documented in the SDM. Here is the
relevant documentation:

Hex   Dec  Name                     Scope
140H  320  MISC_FEATURE_ENABLES     Thread
           0    Reserved
           1    If set to 1, the MONITOR and MWAIT instructions do not
                cause invalid-opcode exceptions when executed with CPL > 0
                or in virtual-8086 mode. If MWAIT is executed when CPL > 0
                or in virtual-8086 mode, and if EAX indicates a C-state
                other than C0 or C1, the instruction operates as if EAX
                indicated the C-state C1.
           63:2 Reserved

Signed-off-by: Grzegorz Andrejczuk <grzegorz.andrejczuk@...el.com>
Cc: Piotr.Luc@...el.com
Cc: dave.hansen@...ux.intel.com
Link: http://lkml.kernel.org/r/1484918557-15481-2-git-send-email-grzegorz.andrejczuk@intel.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 arch/x86/include/asm/msr-index.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 710273c..00293a9 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -543,6 +543,11 @@
 #define MSR_IA32_MISC_ENABLE_IP_PREF_DISABLE_BIT	39
 #define MSR_IA32_MISC_ENABLE_IP_PREF_DISABLE		(1ULL << MSR_IA32_MISC_ENABLE_IP_PREF_DISABLE_BIT)
 
+/* MISC_FEATURE_ENABLES non-architectural features */
+#define MSR_MISC_FEATURE_ENABLES	0x00000140
+
+#define MSR_MISC_FEATURE_ENABLES_RING3MWAIT_BIT		1
+
 #define MSR_IA32_TSC_DEADLINE		0x000006E0
 
 /* P4/Xeon+ specific */