linux-kernel - [PATCH] x86/cpufeature: Add negative features

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Date:   Wed,  5 Jun 2019 15:02:52 -0700
From:   Aaron Lewis <aaronlewis@...gle.com>
To:     linux-kernel@...r.kernel.org, jmattson@...gle.com,
        pshier@...gle.com, marcorr@...gle.com
Cc:     Aaron Lewis <aaronlewis@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org
Subject: [PATCH] x86/cpufeature: Add negative features

Add the CPUID enumeration for Intel's de-feature bits to accommodate
passing these de-features through to kvm guests.

These de-features are:
 - X86_FEATURE_FDP_EXCPTN_ONLY: If CPUID.(EAX=07H,ECX=0H):EBX[bit 6] = 1, the
   data pointer (FDP) is updated only for the x87 non-control instructions that
   incur unmasked x87 exceptions (from SDM vol 1, section 8.1.8).
 - X86_FEATURE_ZERO_FCS_FDS: If CPUID.(EAX=07H,ECX=0H):EBX[bit 13] = 1, the
   processor deprecates FCS and FDS; it saves each as 0000H (from SDM vol 1,
   section 8.1.8).

Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: x86@...nel.org
Reviewed-by: Jim Mattson <jmattson@...gle.com>
Signed-off-by: Aaron Lewis <aaronlewis@...gle.com>
---
 arch/x86/include/asm/cpufeatures.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 75f27ee2c263..1017b9c7dfe0 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -239,12 +239,14 @@
 #define X86_FEATURE_BMI1		( 9*32+ 3) /* 1st group bit manipulation extensions */
 #define X86_FEATURE_HLE			( 9*32+ 4) /* Hardware Lock Elision */
 #define X86_FEATURE_AVX2		( 9*32+ 5) /* AVX2 instructions */
+#define X86_FEATURE_FDP_EXCPTN_ONLY	( 9*32+ 6) /* "" FPU data pointer updated only on x87 exceptions */
 #define X86_FEATURE_SMEP		( 9*32+ 7) /* Supervisor Mode Execution Protection */
 #define X86_FEATURE_BMI2		( 9*32+ 8) /* 2nd group bit manipulation extensions */
 #define X86_FEATURE_ERMS		( 9*32+ 9) /* Enhanced REP MOVSB/STOSB instructions */
 #define X86_FEATURE_INVPCID		( 9*32+10) /* Invalidate Processor Context ID */
 #define X86_FEATURE_RTM			( 9*32+11) /* Restricted Transactional Memory */
 #define X86_FEATURE_CQM			( 9*32+12) /* Cache QoS Monitoring */
+#define X86_FEATURE_ZERO_FCS_FDS	( 9*32+13) /* "" Zero out FPU CS and FPU DS */
 #define X86_FEATURE_MPX			( 9*32+14) /* Memory Protection Extension */
 #define X86_FEATURE_RDT_A		( 9*32+15) /* Resource Director Technology Allocation */
 #define X86_FEATURE_AVX512F		( 9*32+16) /* AVX-512 Foundation */
-- 
2.22.0.rc1.311.g5d7573a151-goog