[PATCH 3.2 074/200] s390/dump: Fix dump memory detection

[Ben Hutchings]

3.2.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 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"

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