From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Date: Thu, 19 Feb 2015 16:53:16 +0000 (+0100)
Subject: s390/spinlock: disabled compare-and-delay by default
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=61b0b01686d482205db14987826e1a11dd17d65c;p=linux-beck.git

s390/spinlock: disabled compare-and-delay by default

Until we have hard performance data about the effects of CAD in the
spinlock loop disable the instruction by default.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index 70a329450901..4427ab7ac23a 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -393,17 +393,19 @@ static __init void detect_machine_facilities(void)
 		S390_lowcore.machine_flags |= MACHINE_FLAG_TLB_LC;
 	if (test_facility(129))
 		S390_lowcore.machine_flags |= MACHINE_FLAG_VX;
-	if (test_facility(128))
-		S390_lowcore.machine_flags |= MACHINE_FLAG_CAD;
 #endif
 }
 
-static int __init nocad_setup(char *str)
+static int __init cad_setup(char *str)
 {
-	S390_lowcore.machine_flags &= ~MACHINE_FLAG_CAD;
+	int val;
+
+	get_option(&str, &val);
+	if (val && test_facility(128))
+		S390_lowcore.machine_flags |= MACHINE_FLAG_CAD;
 	return 0;
 }
-early_param("nocad", nocad_setup);
+early_param("cad", cad_setup);
 
 static int __init cad_init(void)
 {