1 files changed, 3 insertions, 1 deletions

diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
index c2502eb9aa83..a4805b3b4095 100644
--- a/arch/x86/kernel/acpi/cstate.c
+++ b/arch/x86/kernel/acpi/cstate.c
@@ -56,6 +56,7 @@ static struct cstate_entry *cpu_cstate_entry;	/* per CPU ptr */
 static short mwait_supported[ACPI_PROCESSOR_MAX_POWER];
 
 #define MWAIT_SUBSTATE_MASK     (0xf)
+#define MWAIT_CSTATE_MASK       (0xf)
 #define MWAIT_SUBSTATE_SIZE     (4)
 
 #define CPUID_MWAIT_LEAF (5)
@@ -98,7 +99,8 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu,
         cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);
 
         /* Check whether this particular cx_type (in CST) is supported or not */
-        cstate_type = (cx->address >> MWAIT_SUBSTATE_SIZE) + 1;
+        cstate_type = ((cx->address >> MWAIT_SUBSTATE_SIZE) &
+                        MWAIT_CSTATE_MASK) + 1;
         edx_part = edx >> (cstate_type * MWAIT_SUBSTATE_SIZE);
         num_cstate_subtype = edx_part & MWAIT_SUBSTATE_MASK;