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-rw-r--r--arch/x86/kernel/acpi/cstate.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
index c2502eb9aa8..a4805b3b409 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;