[PATCH 1/6] lsmem: display global memmap on memory parameter

[Sumanth Korikkar <sumanthk@linux.ibm.com>]

Display the output of global memmap-on-memory parameter for memory
hotplug. Retrieve the details via
/sys/module/memory_hotplug/parameters/memmap_on_memory.

lsmem
RANGE                                 SIZE  STATE REMOVABLE BLOCK
0x0000000000000000-0x00000001ffffffff   8G online       yes  0-63

Memory block size:                128M
Total online memory:                8G
Total offline memory:               0B
Memmap on memory parameter:        yes

Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
---
 sys-utils/lsmem.1.adoc |  2 ++
 sys-utils/lsmem.c      | 29 +++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/sys-utils/lsmem.1.adoc b/sys-utils/lsmem.1.adoc
index d588051a8..9c9397631 100644
--- a/sys-utils/lsmem.1.adoc
+++ b/sys-utils/lsmem.1.adoc
@@ -28,6 +28,8 @@ Not all columns are supported on all systems. If an unsupported column is specif
 
 Use the *--help* option to see the columns description.
 
+Memmap on memory parameter output displays the globally enabled memmap-on-memory setting for memory_hotplug. This is typically set on the kernel command line via memory_hotplug.memmap_on_memory.
+
 == OPTIONS
 
 *-a*, *--all*::
diff --git a/sys-utils/lsmem.c b/sys-utils/lsmem.c
index 39967bfc9..ea818d6dc 100644
--- a/sys-utils/lsmem.c
+++ b/sys-utils/lsmem.c
@@ -306,8 +306,25 @@ static void fill_scols_table(struct lsmem *lsmem)
 		add_scols_line(lsmem, &lsmem->blocks[i]);
 }
 
+static int get_memmap_mode(char *res, char *src, int len)
+{
+	if (!strncmp(src, "Y", 1))
+		strncpy(res, "yes", len);
+	else if (!strncmp(src, "N", 1))
+		strncpy(res, "no", len);
+	else if (!strncmp(src, "force", 5))
+		strncpy(res, "force", len);
+	else
+		return -1;
+	return 0;
+}
+
 static void print_summary(struct lsmem *lsmem)
 {
+	const char *path = "/sys/module/memory_hotplug/parameters/memmap_on_memory";
+	char buf[8], res[8];
+	FILE *memmap;
+
 	if (lsmem->bytes) {
 		printf("%-32s %15"PRId64"\n",_("Memory block size:"), lsmem->block_size);
 		printf("%-32s %15"PRId64"\n",_("Total online memory:"), lsmem->mem_online);
@@ -327,6 +344,18 @@ static void print_summary(struct lsmem *lsmem)
 			printf("%-32s %5s\n",_("Total offline memory:"), p);
 		free(p);
 	}
+	memmap = fopen(path, "r");
+	if (!memmap)
+		return;
+	if (fgets(buf, sizeof(buf), memmap)) {
+		if (!get_memmap_mode(res, buf, sizeof(res))) {
+			if (lsmem->bytes)
+				printf("%-32s %15s\n", _("Memmap on memory parameter:"), res);
+			else
+				printf("%-32s %5s\n", _("Memmap on memory parameter:"), res);
+		}
+	}
+	fclose(memmap);
 }
 
 static int memory_block_get_node(struct lsmem *lsmem, char *name)
-- 
2.48.1