s390/mem_detect: limit memory detection loop to "mem=" parameter

The current memory detection loop will detect all present memory of
a machine. This is true even if the user specified the "mem=" parameter
on the kernel command line.
This can be a problem since the memory detection may cause a fully
populated host page table for the guest, even for those parts of the
memory that the guest will never use afterwards.

So fix this and only detect memory up to a user supplied "mem=" limit
if specified.

Reported-by: Michael Johanssen <johanssn@de.ibm.com>
Reviewed-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

3 files changed, 2 insertions, 3 deletions

diff --git a/arch/s390/kernel/crash_dump.c b/arch/s390/kernel/crash_dump.c
index fb8d8781a011..30b7f63aa4e8 100644
--- a/arch/s390/kernel/crash_dump.c
+++ b/arch/s390/kernel/crash_dump.c
@@ -88,7 +88,7 @@ static struct mem_chunk *get_memory_layout(void)
         struct mem_chunk *chunk_array;
 
         chunk_array = kzalloc_panic(MEMORY_CHUNKS * sizeof(struct mem_chunk));
-        detect_memory_layout(chunk_array);
+        detect_memory_layout(chunk_array, 0);
         create_mem_hole(chunk_array, OLDMEM_BASE, OLDMEM_SIZE, CHUNK_CRASHK);
         return chunk_array;
 }
diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index bda011e2f8ae..dc8770d7173c 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -482,7 +482,6 @@ void __init startup_init(void)
         detect_machine_facilities();
         setup_topology();
         sclp_facilities_detect();
-        detect_memory_layout(memory_chunk);
 #ifdef CONFIG_DYNAMIC_FTRACE
         S390_lowcore.ftrace_func = (unsigned long)ftrace_caller;
 #endif
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 555f1895972e..cdd9ec0a6fc0 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -1066,7 +1066,7 @@ void __init setup_arch(char **cmdline_p)
                 memcpy(&uaccess, &uaccess_std, sizeof(uaccess));
 
         parse_early_param();
-
+        detect_memory_layout(memory_chunk, memory_end);
         os_info_init();
         setup_ipl();
         reserve_oldmem();