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Date: Sun, 27 Nov 2016 19:05:18 -0800 From: Kyle Huey <me@...ehuey.com> To: Robert O'Callahan <robert@...llahan.org>, Thomas Gleixner <tglx@...utronix.de>, Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org, Paolo Bonzini <pbonzini@...hat.com>, Radim Krčmář <rkrcmar@...hat.com>, Jeff Dike <jdike@...toit.com>, Richard Weinberger <richard@....at>, Alexander Viro <viro@...iv.linux.org.uk>, Shuah Khan <shuah@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, Borislav Petkov <bp@...e.de>, Peter Zijlstra <peterz@...radead.org>, Boris Ostrovsky <boris.ostrovsky@...cle.com>, Len Brown <len.brown@...el.com>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, Dmitry Safonov <dsafonov@...tuozzo.com>, David Matlack <dmatlack@...gle.com>, Nadav Amit <nadav.amit@...il.com>, Andi Kleen <andi@...stfloor.org> Cc: linux-kernel@...r.kernel.org, user-mode-linux-devel@...ts.sourceforge.net, user-mode-linux-user@...ts.sourceforge.net, linux-fsdevel@...r.kernel.org, linux-kselftest@...r.kernel.org, kvm@...r.kernel.org Subject: [PATCH v13 5/8] x86/cpufeature: Detect CPUID faulting support Intel supports faulting on the CPUID instruction beginning with Ivy Bridge. When enabled, the processor will fault on attempts to execute the CPUID instruction with CPL>0. This will allow a ptracer to emulate the CPUID instruction. Bit 31 of MSR_PLATFORM_INFO advertises support for this feature. It is documented in detail in Section 2.3.2 of https://bugzilla.kernel.org/attachment.cgi?id=243991 Detect support for this feature and expose it as X86_FEATURE_CPUID_FAULT. Signed-off-by: Kyle Huey <khuey@...ehuey.com> Reviewed-by: Borislav Petkov <bp@...e.de> --- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/msr-index.h | 2 ++ arch/x86/kernel/cpu/intel.c | 12 ++++++++++++ 3 files changed, 15 insertions(+) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index a396292..85f853f 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -182,16 +182,17 @@ /* * Auxiliary flags: Linux defined - For features scattered in various * CPUID levels like 0x6, 0xA etc, word 7. * * Reuse free bits when adding new feature flags! */ +#define X86_FEATURE_CPUID_FAULT ( 7*32+ 0) /* Intel CPUID faulting */ #define X86_FEATURE_CPB ( 7*32+ 2) /* AMD Core Performance Boost */ #define X86_FEATURE_EPB ( 7*32+ 3) /* IA32_ENERGY_PERF_BIAS support */ #define X86_FEATURE_HW_PSTATE ( 7*32+ 8) /* AMD HW-PState */ #define X86_FEATURE_PROC_FEEDBACK ( 7*32+ 9) /* AMD ProcFeedbackInterface */ #define X86_FEATURE_INTEL_PT ( 7*32+15) /* Intel Processor Trace */ #define X86_FEATURE_AVX512_4VNNIW (7*32+16) /* AVX-512 Neural Network Instructions */ diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h index 78f3760..3ac0acf 100644 --- a/arch/x86/include/asm/msr-index.h +++ b/arch/x86/include/asm/msr-index.h @@ -36,16 +36,18 @@ #define EFER_LMSLE (1<<_EFER_LMSLE) #define EFER_FFXSR (1<<_EFER_FFXSR) /* Intel MSRs. Some also available on other CPUs */ #define MSR_IA32_PERFCTR0 0x000000c1 #define MSR_IA32_PERFCTR1 0x000000c2 #define MSR_FSB_FREQ 0x000000cd #define MSR_PLATFORM_INFO 0x000000ce +#define MSR_PLATFORM_INFO_CPUID_FAULT_BIT 31 +#define MSR_PLATFORM_INFO_CPUID_FAULT BIT_ULL(MSR_PLATFORM_INFO_CPUID_FAULT_BIT) #define MSR_NHM_SNB_PKG_CST_CFG_CTL 0x000000e2 #define NHM_C3_AUTO_DEMOTE (1UL << 25) #define NHM_C1_AUTO_DEMOTE (1UL << 26) #define ATM_LNC_C6_AUTO_DEMOTE (1UL << 25) #define SNB_C1_AUTO_UNDEMOTE (1UL << 27) #define SNB_C3_AUTO_UNDEMOTE (1UL << 28) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index fcd484d..12ddddf 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -447,16 +447,26 @@ static void intel_bsp_resume(struct cpuinfo_x86 *c) { /* * MSR_IA32_ENERGY_PERF_BIAS is lost across suspend/resume, * so reinitialize it properly like during bootup: */ init_intel_energy_perf(c); } +static void init_intel_misc_features(struct cpuinfo_x86 *c) +{ + u64 msr; + + if (!rdmsrl_safe(MSR_PLATFORM_INFO, &msr)) { + if (msr & MSR_PLATFORM_INFO_CPUID_FAULT) + set_cpu_cap(c, X86_FEATURE_CPUID_FAULT); + } +} + static void init_intel(struct cpuinfo_x86 *c) { unsigned int l2 = 0; early_init_intel(c); intel_workarounds(c); @@ -560,16 +570,18 @@ static void init_intel(struct cpuinfo_x86 *c) /* Work around errata */ srat_detect_node(c); if (cpu_has(c, X86_FEATURE_VMX)) detect_vmx_virtcap(c); init_intel_energy_perf(c); + + init_intel_misc_features(c); } #ifdef CONFIG_X86_32 static unsigned int intel_size_cache(struct cpuinfo_x86 *c, unsigned int size) { /* * Intel PIII Tualatin. This comes in two flavours. * One has 256kb of cache, the other 512. We have no way -- 2.10.2
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