v4.19.13 snapshot.
diff --git a/arch/s390/mm/mem_detect.c b/arch/s390/mm/mem_detect.c
new file mode 100644
index 0000000..21f6c82
--- /dev/null
+++ b/arch/s390/mm/mem_detect.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright IBM Corp. 2008, 2009
+ *
+ * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/memblock.h>
+#include <linux/init.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <asm/ipl.h>
+#include <asm/sclp.h>
+#include <asm/setup.h>
+
+#define CHUNK_READ_WRITE 0
+#define CHUNK_READ_ONLY 1
+
+static inline void memblock_physmem_add(phys_addr_t start, phys_addr_t size)
+{
+ memblock_dbg("memblock_physmem_add: [%#016llx-%#016llx]\n",
+ start, start + size - 1);
+ memblock_add_range(&memblock.memory, start, size, 0, 0);
+ memblock_add_range(&memblock.physmem, start, size, 0, 0);
+}
+
+void __init detect_memory_memblock(void)
+{
+ unsigned long memsize, rnmax, rzm, addr, size;
+ int type;
+
+ rzm = sclp.rzm;
+ rnmax = sclp.rnmax;
+ memsize = rzm * rnmax;
+ if (!rzm)
+ rzm = 1UL << 17;
+ max_physmem_end = memsize;
+ addr = 0;
+ /* keep memblock lists close to the kernel */
+ memblock_set_bottom_up(true);
+ do {
+ size = 0;
+ /* assume lowcore is writable */
+ type = addr ? tprot(addr) : CHUNK_READ_WRITE;
+ do {
+ size += rzm;
+ if (max_physmem_end && addr + size >= max_physmem_end)
+ break;
+ } while (type == tprot(addr + size));
+ if (type == CHUNK_READ_WRITE || type == CHUNK_READ_ONLY) {
+ if (max_physmem_end && (addr + size > max_physmem_end))
+ size = max_physmem_end - addr;
+ memblock_physmem_add(addr, size);
+ }
+ addr += size;
+ } while (addr < max_physmem_end);
+ memblock_set_bottom_up(false);
+ if (!max_physmem_end)
+ max_physmem_end = memblock_end_of_DRAM();
+ memblock_dump_all();
+}