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>

diff --git a/arch/s390/include/asm/bitops.h b/arch/s390/include/asm/bitops.h
index 6038349c8410545e696f2f7c1c301bdeb6b1defe..16df62dde094f334d75f731c5f1bbc78375f9880 100644 (file)
--- 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 fd8db63dfc942a211d9dfe95b8c2bff88b90ed8d..429afcc480cb2e86c7e684e81c6f1f1160ee3b05 100644 (file)
--- 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)