x86, mm: introduce vmem_altmap to augment vmemmap_populate()

In support of providing struct page for large persistent memory
capacities, use struct vmem_altmap to change the default policy for
allocating memory for the memmap array.  The default vmemmap_populate()
allocates page table storage area from the page allocator.  Given
persistent memory capacities relative to DRAM it may not be feasible to
store the memmap in 'System Memory'.  Instead vmem_altmap represents
pre-allocated "device pages" to satisfy vmemmap_alloc_block_buf()
requests.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: kbuild test robot <lkp@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 25409714160e..7ca3fe6ef92d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -43,6 +43,7 @@
 #include <linux/vmalloc.h>
 #include <linux/vmstat.h>
 #include <linux/mempolicy.h>
+#include <linux/memremap.h>
 #include <linux/stop_machine.h>
 #include <linux/sort.h>
 #include <linux/pfn.h>
@@ -4485,8 +4486,9 @@ static inline unsigned long wait_table_bits(unsigned long size)
 void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
                 unsigned long start_pfn, enum memmap_context context)
 {
-        pg_data_t *pgdat = NODE_DATA(nid);
+        struct vmem_altmap *altmap = to_vmem_altmap(__pfn_to_phys(start_pfn));
         unsigned long end_pfn = start_pfn + size;
+        pg_data_t *pgdat = NODE_DATA(nid);
         unsigned long pfn;
         struct zone *z;
         unsigned long nr_initialised = 0;
@@ -4494,6 +4496,13 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
         if (highest_memmap_pfn < end_pfn - 1)
                 highest_memmap_pfn = end_pfn - 1;
 
+        /*
+         * Honor reservation requested by the driver for this ZONE_DEVICE
+         * memory
+         */
+        if (altmap && start_pfn == altmap->base_pfn)
+                start_pfn += altmap->reserve;
+
         z = &pgdat->node_zones[zone];
         for (pfn = start_pfn; pfn < end_pfn; pfn++) {
                 /*