[PATCH v3 8/9] s390/percpu: Provide arch_this_cpu_write() implementation

[Heiko Carstens]

Provide an s390 specific implementation of arch_this_cpu_write()
instead of the generic variant. The generic variant uses a quite
expensive raw_local_irq_save() / raw_local_irq_restore() pair.

Get rid of this by providing an own variant which makes use of the new
percpu code section infrastructure.

With this the text size of the kernel image is reduced by ~1k (defconfig).

Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
---
 arch/s390/include/asm/percpu.h | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/arch/s390/include/asm/percpu.h b/arch/s390/include/asm/percpu.h
index abd774fdd73a..44867e7ed0df 100644
--- a/arch/s390/include/asm/percpu.h
+++ b/arch/s390/include/asm/percpu.h
@@ -271,6 +271,36 @@ do {									\
 #define this_cpu_read_4(pcp) arch_this_cpu_read(pcp, "l")
 #define this_cpu_read_8(pcp) arch_this_cpu_read(pcp, "lg")
 
+#define arch_this_cpu_write(pcp, val, op)				\
+do {									\
+	unsigned long lc_pcpr, lc_pcpo;					\
+	typedef typeof(pcp) pcp_op_T__;					\
+	pcp_op_T__ *ptr__, val__ = (val);				\
+									\
+	lc_pcpr = offsetof(struct lowcore, percpu_register);		\
+	lc_pcpo = offsetof(struct lowcore, percpu_offset);		\
+	ptr__ = PERCPU_PTR(&(pcp));					\
+	asm_inline volatile(						\
+		MVIY_PERCPU("%[disppcpr]", "%[dispaltpcpr]", "%[ptr__]")\
+		AG_ALT("%[disppcpo]", "%[dispaltpcpo]", "%[ptr__]")	\
+		op "    %[val__],0(%[ptr__])\n"				\
+		MVIY_ALT("%[disppcpr]", "%[dispaltpcpr]", "%%r0")	\
+		: [ptr__] "+&a" (ptr__), "=m" (*ptr__),			\
+		  "=m" (((struct lowcore *)0)->percpu_register)		\
+		: [val__] "d" (val__),					\
+		  [disppcpr] "i" (lc_pcpr),				\
+		  [disppcpo] "i" (lc_pcpo),				\
+		  [dispaltpcpr] "i" (lc_pcpr + LOWCORE_ALT_ADDRESS),	\
+		  [dispaltpcpo] "i" (lc_pcpo + LOWCORE_ALT_ADDRESS),	\
+		  "m" (((struct lowcore *)0)->percpu_offset)		\
+		: "cc");						\
+} while (0)
+
+#define this_cpu_write_1(pcp, val) arch_this_cpu_write(pcp, val, "stc")
+#define this_cpu_write_2(pcp, val) arch_this_cpu_write(pcp, val, "sth")
+#define this_cpu_write_4(pcp, val) arch_this_cpu_write(pcp, val, "st")
+#define this_cpu_write_8(pcp, val) arch_this_cpu_write(pcp, val, "stg")
+
 #define arch_this_cpu_cmpxchg(pcp, oval, nval)				\
 ({									\
 	typedef typeof(pcp) pcp_op_T__;					\
-- 
2.51.0