[PATCH v2 4/7] mm, devm_memremap_pages: Add MEMORY_DEVICE_PRIVATE support

[Dan Williams <dan.j.williams@intel.com>]

In preparation for consolidating all ZONE_DEVICE enabling via
devm_memremap_pages(), teach it how to handle the constraints of
MEMORY_DEVICE_PRIVATE ranges.

Cc: Christoph Hellwig <hch@lst.de>
Cc: "JA(C)rA'me Glisse" <jglisse@redhat.com>
Reported-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 kernel/memremap.c |   38 ++++++++++++++++++++++++++++++++------
 1 file changed, 32 insertions(+), 6 deletions(-)

diff --git a/kernel/memremap.c b/kernel/memremap.c
index dfec0801f652..89eed25e2a80 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -303,8 +303,13 @@ static void devm_memremap_pages_release(void *data)
 		- align_start;
 
 	mem_hotplug_begin();
-	arch_remove_memory(align_start, align_size, pgmap->altmap_valid ?
-			&pgmap->altmap : NULL);
+	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
+		pfn = align_start >> PAGE_SHIFT;
+		__remove_pages(page_zone(pfn_to_page(pfn)), pfn,
+				align_size >> PAGE_SHIFT, NULL);
+	} else
+		arch_remove_memory(align_start, align_size,
+				pgmap->altmap_valid ? &pgmap->altmap : NULL);
 	mem_hotplug_done();
 
 	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
@@ -388,11 +393,32 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap,
 		goto err_pfn_remap;
 
 	mem_hotplug_begin();
-	error = arch_add_memory(nid, align_start, align_size, altmap, false);
-	if (!error)
-		move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
-					align_start >> PAGE_SHIFT,
+
+	/*
+	 * For device private memory we call add_pages() as we only need to
+	 * allocate and initialize struct page for the device memory. More-
+	 * over the device memory is un-accessible thus we do not want to
+	 * create a linear mapping for the memory like arch_add_memory()
+	 * would do.
+	 *
+	 * For all other device memory types, which are accessible by
+	 * the CPU, we do want the linear mapping and thus use
+	 * arch_add_memory().
+	 */
+	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
+		error = add_pages(nid, align_start >> PAGE_SHIFT,
+				align_size >> PAGE_SHIFT, NULL, false);
+	} else {
+		struct zone *zone;
+
+		error = arch_add_memory(nid, align_start, align_size, altmap,
+				false);
+		zone = &NODE_DATA(nid)->node_zones[ZONE_DEVICE];
+		if (!error)
+			move_pfn_range_to_zone(zone, align_start >> PAGE_SHIFT,
 					align_size >> PAGE_SHIFT, altmap);
+	}
+
 	mem_hotplug_done();
 	if (error)
 		goto err_add_memory;