From 4ae803253e4649803dc6e972bb5e59fc107cf474 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Tue, 17 Sep 2013 09:48:44 +0200
Subject: [PATCH] s390/bitops: optimize set_bit() for constant values
Since zEC12 we have the interlocked-access facility 2 which allows to
use the instructions ni/oi/xi to update a single byte in storage with
compare-and-swap semantics.
So change set_bit(), clear_bit() and change_bit() to generate such code
instead of a compare-and-swap loop (or using the load-and-* instruction
family), if possible.
This reduces the text segment by yet another 8KB (defconfig).
Alternatively the long displacement variants niy/oiy/xiy could have
been used, but the extended displacement field is usually not needed
and therefore would only increase the size of the text segment again.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
arch/s390/include/asm/bitops.h | 36 ++++++++++++++++++++++++++++++++++
arch/s390/kernel/head.S | 2 +-
2 files changed, 37 insertions(+), 1 deletion(-)
diff --git a/arch/s390/include/asm/bitops.h b/arch/s390/include/asm/bitops.h
index 6038349c8410..16df62dde094 100644
--- a/arch/s390/include/asm/bitops.h
+++ b/arch/s390/include/asm/bitops.h
@@ -151,6 +151,18 @@ static inline void set_bit(unsigned long nr, volatile unsigned long *ptr)
unsigned long *addr = __bitops_word(nr, ptr);
unsigned long mask;
+#ifdef CONFIG_HAVE_MARCH_ZEC12_FEATURES
+ if (__builtin_constant_p(nr)) {
+ unsigned char *caddr = __bitops_byte(nr, ptr);
+
+ asm volatile(
+ "oi %0,%b1\n"
+ : "+Q" (*caddr)
+ : "i" (1 << (nr & 7))
+ : "cc");
+ return;
+ }
+#endif
mask = 1UL << (nr & (BITS_PER_LONG - 1));
__BITOPS_LOOP(addr, mask, __BITOPS_OR);
}
@@ -160,6 +172,18 @@ static inline void clear_bit(unsigned long nr, volatile unsigned long *ptr)
unsigned long *addr = __bitops_word(nr, ptr);
unsigned long mask;
+#ifdef CONFIG_HAVE_MARCH_ZEC12_FEATURES
+ if (__builtin_constant_p(nr)) {
+ unsigned char *caddr = __bitops_byte(nr, ptr);
+
+ asm volatile(
+ "ni %0,%b1\n"
+ : "+Q" (*caddr)
+ : "i" (~(1 << (nr & 7)))
+ : "cc");
+ return;
+ }
+#endif
mask = ~(1UL << (nr & (BITS_PER_LONG - 1)));
__BITOPS_LOOP(addr, mask, __BITOPS_AND);
}
@@ -169,6 +193,18 @@ static inline void change_bit(unsigned long nr, volatile unsigned long *ptr)
unsigned long *addr = __bitops_word(nr, ptr);
unsigned long mask;
+#ifdef CONFIG_HAVE_MARCH_ZEC12_FEATURES
+ if (__builtin_constant_p(nr)) {
+ unsigned char *caddr = __bitops_byte(nr, ptr);
+
+ asm volatile(
+ "xi %0,%b1\n"
+ : "+Q" (*caddr)
+ : "i" (1 << (nr & 7))
+ : "cc");
+ return;
+ }
+#endif
mask = 1UL << (nr & (BITS_PER_LONG - 1));
__BITOPS_LOOP(addr, mask, __BITOPS_XOR);
}
diff --git a/arch/s390/kernel/head.S b/arch/s390/kernel/head.S
index fd8db63dfc94..429afcc480cb 100644
--- a/arch/s390/kernel/head.S
+++ b/arch/s390/kernel/head.S
@@ -437,7 +437,7 @@ ENTRY(startup_kdump)
#if defined(CONFIG_64BIT)
#if defined(CONFIG_MARCH_ZEC12)
- .long 3, 0xc100efe3, 0xf46ce000, 0x00400000
+ .long 3, 0xc100efe3, 0xf46ce800, 0x00400000
#elif defined(CONFIG_MARCH_Z196)
.long 2, 0xc100efe3, 0xf46c0000
#elif defined(CONFIG_MARCH_Z10)