---

yaml
---
r: 136526
b: refs/heads/master
c: b38b066
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 75a048119e76540d73132cfc8e0fa0c0a8bb6c83
+refs/heads/master: b38b0665905538e76e26f2a4c686179abb1f69f6

trunk/arch/x86/kernel/cpu/common.c

@@ -212,6 +212,49 @@ 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;
@@ -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;