s390/dump: Fix dump memory detection

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.

Cc: <stable@vger.kernel.org>
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/mm/page-states.c b/arch/s390/mm/page-states.c
index a90d45e9dfb0cbb7b1dce5fb8441a249dc0556c3..27c50f4d90cb32ce97db6004ce450096b807655c 100644 (file)
--- 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"