x86: unmask CPUID levels on Intel CPUs

If the CPUID limit bit in MSR_IA32_MISC_ENABLE is set, clear it to
make all CPUID information available. This is required for some
features to work, such as MWAIT in cpuidle, get cpu topology, XSAVE,
etc.

Signed-off-by: Wei Gang <gang.wei@intel.com>

xen/arch/x86/cpu/intel.c

@@ -90,6 +90,20 @@ void __devinit early_intel_workaround(struct cpuinfo_x86 *c)
 	/* Netburst reports 64 bytes clflush size, but does IO in 128 bytes */
 	if (c->x86 == 15 && c->x86_cache_alignment == 64)
 		c->x86_cache_alignment = 128;
+
+	/* Unmask CPUID levels if masked: */
+	if (c->x86 > 6 || (c->x86 == 6 && c->x86_model >= 0xd)) {
+		u64 misc_enable;
+
+		rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable);
+
+		if (misc_enable & MSR_IA32_MISC_ENABLE_LIMIT_CPUID) {
+			misc_enable &= ~MSR_IA32_MISC_ENABLE_LIMIT_CPUID;
+			wrmsrl(MSR_IA32_MISC_ENABLE, misc_enable);
+			c->cpuid_level = cpuid_eax(0);
+			printk("revised cpuid_level = %d\n", c->cpuid_level);
+		}
+	}
 }
 
 /*

xen/include/asm-x86/msr-index.h

@@ -324,6 +324,7 @@
 #define MSR_IA32_MISC_ENABLE_BTS_UNAVAIL  (1<<11)
 #define MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL (1<<12)
 #define MSR_IA32_MISC_ENABLE_MONITOR_ENABLE (1<<18)
+#define MSR_IA32_MISC_ENABLE_LIMIT_CPUID  (1<<22)
 #define MSR_IA32_MISC_ENABLE_XTPR_DISABLE (1<<23)
 
 /* Intel Model 6 */