[RFC PATCH 4/6] mm/page_alloc: adjust the start,end in dax pmem kmem case

[Jia He <justin.he@arm.com>]

There are 3 cases when doing online pages:
 - normal RAM, should be aligned with memory block size
 - persistent memory with ZONE_DEVICE
 - persistent memory used as normal RAM (kmem) with ZONE_NORMAL, this patch
   tries to adjust the start_pfn/end_pfn after finding the corresponding
   resource range.

Without this patch, the check of __init_single_page when doing online memory
will be failed because those pages haven't been mapped in mmu(not present
from mmu's point of view).

Signed-off-by: Jia He <justin.he@arm.com>
---
 mm/page_alloc.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e028b87ce294..13216ab3623f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5971,6 +5971,20 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 		if (start_pfn == altmap->base_pfn)
 			start_pfn += altmap->reserve;
 		end_pfn = altmap->base_pfn + vmem_altmap_offset(altmap);
+	} else {
+		struct resource res;
+		int ret;
+
+		/* adjust the start,end in dax pmem kmem case */
+		ret = find_next_iomem_res(start_pfn << PAGE_SHIFT,
+			(end_pfn << PAGE_SHIFT) - 1,
+			IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
+			IORES_DESC_PERSISTENT_MEMORY,
+			false, &res);
+		if (!ret) {
+			start_pfn = PFN_UP(res.start);
+			end_pfn = PFN_DOWN(res.end + 1);
+		}
 	}
 #endif
 
-- 
2.17.1