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@kylehuey.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Grzegorz Andrejczuk <grzegorz.andrejczuk@intel.com>
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: linux-kselftest@vger.kernel.org
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Robert O'Callahan <robert@ocallahan.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: user-mode-linux-user@lists.sourceforge.net
Cc: David Matlack <dmatlack@google.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Link: http://lkml.kernel.org/r/20170320081628.18952-8-khuey@kylehuey.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 26 insertions, 1 deletions

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index b04bb6dfed7f..0fe00446f9ca 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -187,6 +187,7 @@
  * Reuse free bits when adding new feature flags!
  */
 #define X86_FEATURE_RING3MWAIT  ( 7*32+ 0) /* Ring 3 MONITOR/MWAIT */
+#define X86_FEATURE_CPUID_FAULT ( 7*32+ 1) /* 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_CAT_L3      ( 7*32+ 4) /* Cache Allocation Technology L3 */
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index f429b70ebaef..b1f75daca34b 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -45,6 +45,8 @@
 #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_PKG_CST_CONFIG_CONTROL      0x000000e2
 #define NHM_C3_AUTO_DEMOTE              (1UL << 25)
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index e229318d7230..a07f8295c9ed 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -488,6 +488,28 @@ static void intel_bsp_resume(struct cpuinfo_x86 *c)
         init_intel_energy_perf(c);
 }
 
+static void init_cpuid_fault(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_misc_features(struct cpuinfo_x86 *c)
+{
+        u64 msr;
+
+        if (rdmsrl_safe(MSR_MISC_FEATURES_ENABLES, &msr))
+                return;
+
+        /* Check features and update capabilities */
+        init_cpuid_fault(c);
+        probe_xeon_phi_r3mwait(c);
+}
+
 static void init_intel(struct cpuinfo_x86 *c)
 {
         unsigned int l2 = 0;
@@ -602,7 +624,7 @@ static void init_intel(struct cpuinfo_x86 *c)
 
         init_intel_energy_perf(c);
 
-        probe_xeon_phi_r3mwait(c);
+        init_intel_misc_features(c);
 }
 
 #ifdef CONFIG_X86_32