[PATCH 3.12 16/82] s390/dump: Fix dump memory detection

Greg Kroah-Hartman
2014-02-21T00:43:14Z

From: Michael Holzheu <holzheu@linux.vnet.ibm.com>

commit d7736ff5be31edaa4fe5ab62810c64529a24b149 upstream.

Dumps created by kdump or zfcpdump can contain invalid memory holes when
dumping z/VM systems that have memory pressure.

For example:

# zgetdump -i /proc/vmcore.
Memory map:
0000000000000000 - 0000000000bfffff (12 MB)
0000000000e00000 - 00000000014fffff (7 MB)
000000000bd00000 - 00000000f3bfffff (3711 MB)

The memory detection function find_memory_chunks() issues tprot to
find valid memory chunks. In case of CMM it can happen that pages are
marked as unstable via set_page_unstable() in arch_free_page().
If z/VM has released that pages, tprot returns -EFAULT and indicates
a memory hole.

So fix this and switch off CMM in case of kdump or zfcpdump.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/s390/mm/page-states.c | 10 ++++++++++
1 file changed, 10 insertions(+)

--- a/arch/s390/mm/page-states.c
+++ b/arch/s390/mm/page-states.c
@@ -12,6 +12,8 @@
#include <linux/mm.h>
#include <linux/gfp.h>
#include <linux/init.h>
+#include <asm/setup.h>
+#include <asm/ipl.h>

#define ESSA_SET_STABLE 1
#define ESSA_SET_UNUSED 2
@@ -41,6 +43,14 @@ void __init cmma_init(void)

if (!cmma_flag)
return;
+ /*
+ * Disable CMM for dump, otherwise the tprot based memory
+ * detection can fail because of unstable pages.
+ */
+ if (OLDMEM_BASE || ipl_info.type == IPL_TYPE_FCP_DUMP) {
+ cmma_flag = 0;
+ return;
+ }
asm volatile(
" .insn rrf,0xb9ab0000,%1,%1,0,0\n"
"0: la %0,0\n"