[S390] Limit cpu detection to 256 physical cpus.

Saves us more than 65k pointless IPIs.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

4 files changed, 13 insertions, 7 deletions

diff --git a/arch/s390/include/asm/cpu.h b/arch/s390/include/asm/cpu.h
new file mode 100644
index 00000000000..702ad46841c
--- /dev/null
+++ b/arch/s390/include/asm/cpu.h
@@ -0,0 +1,6 @@
+#ifndef _ASM_S390_CPU_H
+#define _ASM_S390_CPU_H
+
+#define MAX_CPU_ADDRESS 255
+
+#endif /* _ASM_S390_CPU_H */
diff --git a/arch/s390/kernel/head.S b/arch/s390/kernel/head.S
index ec688234852..c52b4f7742f 100644
--- a/arch/s390/kernel/head.S
+++ b/arch/s390/kernel/head.S
@@ -27,6 +27,7 @@
 #include <asm/asm-offsets.h>
 #include <asm/thread_info.h>
 #include <asm/page.h>
+#include <asm/cpu.h>
 
 #ifdef CONFIG_64BIT
 #define ARCH_OFFSET     4
diff --git a/arch/s390/kernel/head64.S b/arch/s390/kernel/head64.S
index bdcb3f05bcd..6a250808092 100644
--- a/arch/s390/kernel/head64.S
+++ b/arch/s390/kernel/head64.S
@@ -62,9 +62,9 @@ startup_continue:
         clr     %r11,%r12
         je      5f                      # no more space in prefix array
 4:
-        ahi     %r8,1                           # next cpu (r8 += 1)
-        cl      %r8,.Llast_cpu-.LPG1(%r13)      # is last possible cpu ?
-        jl      1b                              # jump if not last cpu
+        ahi     %r8,1                   # next cpu (r8 += 1)
+        chi     %r8,MAX_CPU_ADDRESS     # is last possible cpu ?
+        jle     1b                      # jump if not last cpu
 5:
         lhi     %r1,2                   # mode 2 = esame (dump)
         j       6f
@@ -130,8 +130,6 @@ startup_continue:
 #ifdef CONFIG_ZFCPDUMP
 .Lcurrent_cpu:
         .long 0x0
-.Llast_cpu:
-        .long 0x0000ffff
 .Lpref_arr_ptr:
         .long zfcpdump_prefix_array
 #endif /* CONFIG_ZFCPDUMP */
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index be2cae08340..9261495ca2c 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -49,6 +49,7 @@
 #include <asm/sclp.h>
 #include <asm/cputime.h>
 #include <asm/vdso.h>
+#include <asm/cpu.h>
 #include "entry.h"
 
 static struct task_struct *current_set[NR_CPUS];
@@ -300,7 +301,7 @@ static int smp_rescan_cpus_sigp(cpumask_t avail)
         logical_cpu = cpumask_first(&avail);
         if (logical_cpu >= nr_cpu_ids)
                 return 0;
-        for (cpu_id = 0; cpu_id <= 65535; cpu_id++) {
+        for (cpu_id = 0; cpu_id <= MAX_CPU_ADDRESS; cpu_id++) {
                 if (cpu_known(cpu_id))
                         continue;
                 __cpu_logical_map[logical_cpu] = cpu_id;
@@ -379,7 +380,7 @@ static void __init smp_detect_cpus(void)
         /* Use sigp detection algorithm if sclp doesn't work. */
         if (sclp_get_cpu_info(info)) {
                 smp_use_sigp_detection = 1;
-                for (cpu = 0; cpu <= 65535; cpu++) {
+                for (cpu = 0; cpu <= MAX_CPU_ADDRESS; cpu++) {
                         if (cpu == boot_cpu_addr)
                                 continue;
                         __cpu_logical_map[CPU_INIT_NO] = cpu;