[S390] fix "mem=" handling in case of standby memory

Standby memory detected with the sclp interface gets always registered
with add_memory calls without considering the limitationt that the
"mem=" kernel paramater implies.
So fix this and only register standby memory that is below the specified
limit.
This fixes zfcpdump since it uses "mem=32M". In case there is appr.
2GB standby memory present all of usable memory would be used for the
struct pages needed for standby memory.

Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/include/asm/setup.h

···
 
 extern struct mem_chunk memory_chunk[];
 extern unsigned long real_memory_size;
+extern int memory_end_set;
+extern unsigned long memory_end;
 
 void detect_memory_layout(struct mem_chunk chunk[]);
 

arch/s390/kernel/setup.c

···
 
 struct mem_chunk __initdata memory_chunk[MEMORY_CHUNKS];
 volatile int __cpu_logical_map[NR_CPUS]; /* logical cpu to cpu address */
-static unsigned long __initdata memory_end;
+
+int __initdata memory_end_set;
+unsigned long __initdata memory_end;
 
 /*
  * This is set up by the setup-routine at boot-time
···
 static int __init early_parse_mem(char *p)
 {
 	memory_end = memparse(p, &p);
+	memory_end_set = 1;
 	return 0;
 }
 early_param("mem", early_parse_mem);
···
 	int i;
 
 #if defined(CONFIG_ZFCPDUMP) || defined(CONFIG_ZFCPDUMP_MODULE)
-	if (ipl_info.type == IPL_TYPE_FCP_DUMP)
+	if (ipl_info.type == IPL_TYPE_FCP_DUMP) {
 		memory_end = ZFCPDUMP_HSA_SIZE;
+		memory_end_set = 1;
+	}
 #endif
 	memory_size = 0;
 	memory_end &= PAGE_MASK;

drivers/s390/char/sclp_cmd.c

···
 #include <linux/memory.h>
 #include <asm/chpid.h>
 #include <asm/sclp.h>
+#include <asm/setup.h>
 
 #include "sclp.h"
 
···
 		goto skip_add;
 	if (start + size > VMEM_MAX_PHYS)
 		size = VMEM_MAX_PHYS - start;
+	if (memory_end_set && (start >= memory_end))
+		goto skip_add;
+	if (memory_end_set && (start + size > memory_end))
+		size = memory_end - start;
 	add_memory(0, start, size);
 skip_add:
 	first_rn = rn;