[Xen-devel] [PATCH v3 2/3] x86 Test and expose CPUID faulting capabilities in /proc/cpuinfo

[Kyle Huey <me@xxxxxxxxxxxx>]

Signed-off-by: Kyle Huey <khuey@xxxxxxxxxxxx>
---
 arch/x86/include/asm/cpufeatures.h |  1 +
 arch/x86/include/asm/msr-index.h   |  1 +
 arch/x86/kernel/cpu/scattered.c    | 14 ++++++++++++++
 3 files changed, 16 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h 
b/arch/x86/include/asm/cpufeatures.h
index 92a8308..78b9d06 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -190,6 +190,7 @@
 
 #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_CPUID_FAULT ( 7*32+ 4) /* Intel CPUID faulting */
 
 #define X86_FEATURE_HW_PSTATE  ( 7*32+ 8) /* AMD HW-PState */
 #define X86_FEATURE_PROC_FEEDBACK ( 7*32+ 9) /* AMD ProcFeedbackInterface */
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 56f4c66..83908d5 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -41,6 +41,7 @@
 #define MSR_IA32_PERFCTR1              0x000000c2
 #define MSR_FSB_FREQ                   0x000000cd
 #define MSR_PLATFORM_INFO              0x000000ce
+#define CPUID_FAULTING_SUPPORT         (1UL << 31)
 
 #define MSR_NHM_SNB_PKG_CST_CFG_CTL    0x000000e2
 #define NHM_C3_AUTO_DEMOTE             (1UL << 25)
diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index 8cb57df..d502da1 100644
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -24,6 +24,17 @@ enum cpuid_regs {
        CR_EBX
 };
 
+static int supports_cpuid_faulting(void)
+{
+       unsigned int lo, hi;
+
+       if (rdmsr_safe(MSR_PLATFORM_INFO, &lo, &hi) == 0 &&
+           (lo & CPUID_FAULTING_SUPPORT))
+               return 1;
+       else
+               return 0;
+}
+
 void init_scattered_cpuid_features(struct cpuinfo_x86 *c)
 {
        u32 max_level;
@@ -54,4 +65,7 @@ void init_scattered_cpuid_features(struct cpuinfo_x86 *c)
                if (regs[cb->reg] & (1 << cb->bit))
                        set_cpu_cap(c, cb->feature);
        }
+
+       if (supports_cpuid_faulting())
+               set_cpu_cap(c, X86_FEATURE_CPUID_FAULT);
 }
-- 
2.9.3


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