linux-kernel - [PATCH v10 1/5] x86/msr: add MSR_MISC_FEATURE

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Message-Id: <1481911204-3713-2-git-send-email-grzegorz.andrejczuk@intel.com>
Date:   Fri, 16 Dec 2016 19:00:00 +0100
From:   Grzegorz Andrejczuk <grzegorz.andrejczuk@...el.com>
To:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Piotr.Luc@...el.com,
        dave.hansen@...ux.intel.com,
        Grzegorz Andrejczuk <grzegorz.andrejczuk@...el.com>
Subject: [PATCH v10 1/5] x86/msr: add MSR_MISC_FEATURE_ENABLES and RING3MWAIT bit

This patch defines new MSR MISC_FEATURE_ENABLES (0x140).
On supported CPUs if bit 1 of this new register 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>
---
 arch/x86/include/asm/msr-index.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 78f3760..55ffae0 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -539,6 +539,12 @@
 #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_MISC_FEATURE_ENABLES_RING3MWAIT		(1ULL << MSR_MISC_FEATURE_ENABLES_RING3MWAIT_BIT)
+
 #define MSR_IA32_TSC_DEADLINE		0x000006E0
 
 /* P4/Xeon+ specific */
-- 
2.5.1