From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: s390/spinlock: use cpu alternatives to enable niai instruction
Patch-mainline: v4.15-rc1
Git-commit: f554be42fd0fd8dd14680c67f2db26b3e7de9670
References: FATE#322614,LTC#160173,bsc#1066354

Summary:     kernel: add niai spinlock optimization
Description: Exploit the semaphore-assist facility introduced with IBM z14
             to improve the system behaviour in case of congested spinlocks.

Upstream-Description:

             s390/spinlock: use cpu alternatives to enable niai instruction

             Enable niai instruction in the spinlock code at run-time for machines
             on which facility 49 is available (zEC12 and newer).

             Signed-off-by: Vasily Gorbik <gor@linux.vnet.ibm.com>
             Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>


Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 arch/s390/include/asm/spinlock.h |    5 ++---
 arch/s390/lib/spinlock.c         |    9 +++------
 2 files changed, 5 insertions(+), 9 deletions(-)

--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -13,6 +13,7 @@
 #include <asm/atomic_ops.h>
 #include <asm/barrier.h>
 #include <asm/processor.h>
+#include <asm/alternative.h>
 
 #define SPINLOCK_LOCKVAL (S390_lowcore.spinlock_lockval)
 
@@ -92,9 +93,7 @@ static inline void arch_spin_unlock(arch
 {
 	typecheck(int, lp->lock);
 	asm volatile(
-#ifdef CONFIG_HAVE_MARCH_ZEC12_FEATURES
-		"	.long	0xb2fa0070\n"	/* NIAI 7 */
-#endif
+		ALTERNATIVE("", ".long 0xb2fa0070", 49)	/* NIAI 7 */
 		"	st	%1,%0\n"
 		: "=Q" (lp->lock) : "d" (0) : "cc", "memory");
 }
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -10,6 +10,7 @@
 #include <linux/spinlock.h>
 #include <linux/init.h>
 #include <linux/smp.h>
+#include <asm/alternative.h>
 #include <asm/io.h>
 
 int spin_retry = -1;
@@ -37,9 +38,7 @@ static inline int arch_load_niai4(int *l
 	int owner;
 
 	asm volatile(
-#ifdef CONFIG_HAVE_MARCH_ZEC12_FEATURES
-		"	.long	0xb2fa0040\n"	/* NIAI 4 */
-#endif
+		ALTERNATIVE("", ".long 0xb2fa0040", 49)	/* NIAI 4 */
 		"	l	%0,%1\n"
 		: "=d" (owner) : "Q" (*lock) : "memory");
        return owner;
@@ -50,9 +49,7 @@ static inline int arch_cmpxchg_niai8(int
 	int expected = old;
 
 	asm volatile(
-#ifdef CONFIG_HAVE_MARCH_ZEC12_FEATURES
-		"	.long	0xb2fa0080\n"	/* NIAI 8 */
-#endif
+		ALTERNATIVE("", ".long 0xb2fa0080", 49)	/* NIAI 8 */
 		"	cs	%0,%3,%1\n"
 		: "=d" (old), "=Q" (*lock)
 		: "0" (old), "d" (new), "Q" (*lock)