1 files changed, 47 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 0f8656361e04..21f086b4c1a8 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -213,6 +213,49 @@ static inline void squash_the_stupid_serial_number(struct cpuinfo_x86 *c)
 #endif
 
 /*
+ * Some CPU features depend on higher CPUID levels, which may not always
+ * be available due to CPUID level capping or broken virtualization
+ * software.  Add those features to this table to auto-disable them.
+ */
+struct cpuid_dependent_feature {
+        u32 feature;
+        u32 level;
+};
+static const struct cpuid_dependent_feature __cpuinitconst
+cpuid_dependent_features[] = {
+        { X86_FEATURE_MWAIT,            0x00000005 },
+        { X86_FEATURE_DCA,              0x00000009 },
+        { X86_FEATURE_XSAVE,            0x0000000d },
+        { 0, 0 }
+};
+
+static void __cpuinit filter_cpuid_features(struct cpuinfo_x86 *c, bool warn)
+{
+        const struct cpuid_dependent_feature *df;
+        for (df = cpuid_dependent_features; df->feature; df++) {
+                /*
+                 * Note: cpuid_level is set to -1 if unavailable, but
+                 * extended_extended_level is set to 0 if unavailable
+                 * and the legitimate extended levels are all negative
+                 * when signed; hence the weird messing around with
+                 * signs here...
+                 */
+                if (cpu_has(c, df->feature) &&
+                    ((s32)df->feature < 0 ?
+                     (u32)df->feature > (u32)c->extended_cpuid_level :
+                     (s32)df->feature > (s32)c->cpuid_level)) {
+                        clear_cpu_cap(c, df->feature);
+                        if (warn)
+                                printk(KERN_WARNING
+                                       "CPU: CPU feature %s disabled "
+                                       "due to lack of CPUID level 0x%x\n",
+                                       x86_cap_flags[df->feature],
+                                       df->level);
+                }
+        }
+}       
+
+/*
  * Naming convention should be: <Name> [(<Codename>)]
  * This table only is used unless init_<vendor>() below doesn't set it;
  * in particular, if CPUID levels 0x80000002..4 are supported, this isn't used
@@ -573,6 +616,7 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 #ifdef CONFIG_SMP
         c->cpu_index = boot_cpu_id;
 #endif
+        filter_cpuid_features(c, false);
 }
 
 void __init early_cpu_init(void)
@@ -706,6 +750,9 @@ static void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
          * we do "generic changes."
          */
 
+        /* Filter out anything that depends on CPUID levels we don't have */
+        filter_cpuid_features(c, true);
+
         /* If the model name is still unset, do table lookup. */
         if (!c->x86_model_id[0]) {
                 char *p;