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

[Dan Williams]

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 <h...@lst.de>
Cc: "Jérôme Glisse" <jgli...@redhat.com>
Reported-by: Logan Gunthorpe <log...@deltatee.com>
Signed-off-by: Dan Williams <dan.j.willi...@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;