This patch enables the directMap counters to be printed in proc/meminfo
for Hash mmu. With this patch on a system with 8G of DRAM we can see the
entire RAM mapped with 16M pagesize:

cat /proc/meminfo |grep -i direct
DirectMap4k:           0 kB
DirectMap64k:          0 kB
DirectMap16M:    8388608 kB
DirectMap16G:          0 kB

Tested with devdax too:
root@buildroot:/# ndctl create-namespace -r region0 -m devdax -s 2G
{
  "dev":"namespace0.0",
  "mode":"devdax",
  "map":"dev",
  "size":"2032.00 MiB (2130.71 MB)",
  "uuid":"aa383ded-cd99-43a0-979f-5225467cfb40",
  "daxregion":{
    "id":0,
    "size":"2032.00 MiB (2130.71 MB)",
    "align":16777216,
    "devices":[
      {
        "chardev":"dax0.0",
        "size":"2032.00 MiB (2130.71 MB)",
        "target_node":0,
        "align":"16.00 MiB (16.78 MB)",
        "mode":"devdax"
      }
    ]
  },
  "align":16777216
}
root@buildroot:/# cat /proc/meminfo |grep -i direct
DirectMap4k:           0 kB
DirectMap64k:          0 kB
DirectMap16M:   10485760 kB
DirectMap16G:          0 kB

root@buildroot:/# ndctl destroy-namespace -f all
destroyed 1 namespace
root@buildroot:/# cat /proc/meminfo |grep -i direct
DirectMap4k:           0 kB
DirectMap64k:          0 kB
DirectMap16M:    8388608 kB
DirectMap16G:          0 kB

Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <redacted>
Cc: Paul Mackerras <redacted>
Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Cc: Donet Tom <redacted>
Cc: <redacted>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 arch/powerpc/mm/book3s64/pgtable.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
index c9431ae7f78a..e3485db7de02 100644
--- a/arch/powerpc/mm/book3s64/pgtable.c
+++ b/arch/powerpc/mm/book3s64/pgtable.c

@@ -510,20 +510,21 @@ atomic_long_t direct_pages_count[MMU_PAGE_COUNT];
 
 void arch_report_meminfo(struct seq_file *m)
 {
-	/*
-	 * Hash maps the memory with one size mmu_linear_psize.
-	 * So don't bother to print these on hash
-	 */
-	if (!radix_enabled())
-		return;
 	seq_printf(m, "DirectMap4k:    %8lu kB\n",
 		   atomic_long_read(&direct_pages_count[MMU_PAGE_4K]) << 2);
-	seq_printf(m, "DirectMap64k:    %8lu kB\n",
+	seq_printf(m, "DirectMap64k:   %8lu kB\n",
 		   atomic_long_read(&direct_pages_count[MMU_PAGE_64K]) << 6);
-	seq_printf(m, "DirectMap2M:    %8lu kB\n",
-		   atomic_long_read(&direct_pages_count[MMU_PAGE_2M]) << 11);
-	seq_printf(m, "DirectMap1G:    %8lu kB\n",
-		   atomic_long_read(&direct_pages_count[MMU_PAGE_1G]) << 20);
+	if (radix_enabled()) {
+		seq_printf(m, "DirectMap2M:    %8lu kB\n",
+			   atomic_long_read(&direct_pages_count[MMU_PAGE_2M]) << 11);
+		seq_printf(m, "DirectMap1G:    %8lu kB\n",
+			   atomic_long_read(&direct_pages_count[MMU_PAGE_1G]) << 20);
+	} else {
+		seq_printf(m, "DirectMap16M:   %8lu kB\n",
+			   atomic_long_read(&direct_pages_count[MMU_PAGE_16M]) << 14);
+		seq_printf(m, "DirectMap16G:   %8lu kB\n",
+			   atomic_long_read(&direct_pages_count[MMU_PAGE_16G]) << 24);
+	}
 }
 #endif /* CONFIG_PROC_FS */
 

-- 
2.51.0