X-Git-Url: http://pileus.org/git/?a=blobdiff_plain;f=arch%2Fx86%2Fkernel%2Fprocess_32.c;h=9f45a51af968be31679923ea94bf83a9e0c60e88;hb=0c07ee38c9d4eb081758f5ad14bbffa7197e1aec;hp=69a69c3f43bb4940c6fa9485b0015debb68f432a;hpb=30d432dfab2bcfd021d352e2058fae6b9405caeb;p=~andy%2Flinux

diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 69a69c3f43b..9f45a51af96 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -285,9 +285,17 @@ static void mwait_idle(void)
 	mwait_idle_with_hints(0, 0);
 }
 
+static int mwait_usable(const struct cpuinfo_x86 *c)
+{
+	if (force_mwait)
+		return 1;
+	/* Any C1 states supported? */
+	return c->cpuid_level >= 5 && ((cpuid_edx(5) >> 4) & 0xf) > 0;
+}
+
 void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
 {
-	if (cpu_has(c, X86_FEATURE_MWAIT)) {
+	if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
 		printk("monitor/mwait feature present.\n");
 		/*
 		 * Skip, if setup has overridden idle.