Use set_pte_at() to assign the PTE pointer returned by alloc_vm_area(),
rather than a direct assignment.

Fixes: 6056e50033d9 ("drm/i915/gem: Support discontiguous lmem object maps")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_pages.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
index 0fee67f34d74..6838cf9bdae6 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
@@ -286,23 +286,34 @@ static void *i915_gem_object_map(struct drm_i915_gem_object *obj,
 	}
 
 	if (i915_gem_object_has_struct_page(obj)) {
+		unsigned long addr = (unsigned long)area->addr;
 		struct sgt_iter iter;
 		struct page *page;
 		pte_t **ptes = mem;
 
-		for_each_sgt_page(page, iter, sgt)
-			**ptes++ = mk_pte(page, pgprot);
+		for_each_sgt_page(page, iter, sgt) {
+			set_pte_at(&init_mm, addr, *ptes, mk_pte(page, pgprot));
+			addr += PAGE_SIZE;
+			ptes++;
+		}
+		GEM_BUG_ON(addr != (unsigned long)area->addr + obj->base.size);
 	} else {
+		unsigned long addr = (unsigned long)area->addr;
 		resource_size_t iomap;
 		struct sgt_iter iter;
 		pte_t **ptes = mem;
-		dma_addr_t addr;
+		dma_addr_t offset;
 
 		iomap = obj->mm.region->iomap.base;
 		iomap -= obj->mm.region->region.start;
 
-		for_each_sgt_daddr(addr, iter, sgt)
-			**ptes++ = iomap_pte(iomap, addr, pgprot);
+		for_each_sgt_daddr(offset, iter, sgt) {
+			set_pte_at(&init_mm, addr, *ptes,
+				   iomap_pte(iomap, offset, pgprot));
+			addr += PAGE_SIZE;
+			ptes++;
+		}
+		GEM_BUG_ON(addr != (unsigned long)area->addr + obj->base.size);
 	}
 	flush_vm_area(area);
 
-- 
2.20.1