diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 21876ee..7bf5ba7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1089,6 +1089,7 @@ static struct ttm_bo_driver amdgpu_bo_driver = {
 	.fault_reserve_notify = &amdgpu_bo_fault_reserve_notify,
 	.io_mem_reserve = &amdgpu_ttm_io_mem_reserve,
 	.io_mem_free = &amdgpu_ttm_io_mem_free,
+	.io_mem_pfn = ttm_bo_default_io_mem_pfn,
 };
 
 int amdgpu_ttm_init(struct amdgpu_device *adev)
diff --git a/drivers/gpu/drm/ast/ast_ttm.c b/drivers/gpu/drm/ast/ast_ttm.c
index 50c910e..e879496 100644
--- a/drivers/gpu/drm/ast/ast_ttm.c
+++ b/drivers/gpu/drm/ast/ast_ttm.c
@@ -236,6 +236,7 @@ struct ttm_bo_driver ast_bo_driver = {
 	.verify_access = ast_bo_verify_access,
 	.io_mem_reserve = &ast_ttm_io_mem_reserve,
 	.io_mem_free = &ast_ttm_io_mem_free,
+	.io_mem_pfn = ttm_bo_default_io_mem_pfn,
 };
 
 int ast_mm_init(struct ast_private *ast)
diff --git a/drivers/gpu/drm/bochs/bochs_mm.c b/drivers/gpu/drm/bochs/bochs_mm.c
index e4c1125..804afbc 100644
--- a/drivers/gpu/drm/bochs/bochs_mm.c
+++ b/drivers/gpu/drm/bochs/bochs_mm.c
@@ -205,6 +205,7 @@ struct ttm_bo_driver bochs_bo_driver = {
 	.verify_access = bochs_bo_verify_access,
 	.io_mem_reserve = &bochs_ttm_io_mem_reserve,
 	.io_mem_free = &bochs_ttm_io_mem_free,
+	.io_mem_pfn = ttm_bo_default_io_mem_pfn,
 };
 
 int bochs_mm_init(struct bochs_device *bochs)
diff --git a/drivers/gpu/drm/cirrus/cirrus_ttm.c b/drivers/gpu/drm/cirrus/cirrus_ttm.c
index f53aa8f..93dbcd3 100644
--- a/drivers/gpu/drm/cirrus/cirrus_ttm.c
+++ b/drivers/gpu/drm/cirrus/cirrus_ttm.c
@@ -236,6 +236,7 @@ struct ttm_bo_driver cirrus_bo_driver = {
 	.verify_access = cirrus_bo_verify_access,
 	.io_mem_reserve = &cirrus_ttm_io_mem_reserve,
 	.io_mem_free = &cirrus_ttm_io_mem_free,
+	.io_mem_pfn = ttm_bo_default_io_mem_pfn,
 };
 
 int cirrus_mm_init(struct cirrus_device *cirrus)
diff --git a/drivers/gpu/drm/mgag200/mgag200_ttm.c b/drivers/gpu/drm/mgag200/mgag200_ttm.c
index 657598b..565a217 100644
--- a/drivers/gpu/drm/mgag200/mgag200_ttm.c
+++ b/drivers/gpu/drm/mgag200/mgag200_ttm.c
@@ -236,6 +236,7 @@ struct ttm_bo_driver mgag200_bo_driver = {
 	.verify_access = mgag200_bo_verify_access,
 	.io_mem_reserve = &mgag200_ttm_io_mem_reserve,
 	.io_mem_free = &mgag200_ttm_io_mem_free,
+	.io_mem_pfn = ttm_bo_default_io_mem_pfn,
 };
 
 int mgag200_mm_init(struct mga_device *mdev)
diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
index 3949a74..978a5e7 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -1570,6 +1570,7 @@ struct ttm_bo_driver nouveau_bo_driver = {
 	.fault_reserve_notify = &nouveau_ttm_fault_reserve_notify,
 	.io_mem_reserve = &nouveau_ttm_io_mem_reserve,
 	.io_mem_free = &nouveau_ttm_io_mem_free,
+	.io_mem_pfn = ttm_bo_default_io_mem_pfn,
 };
 
 struct nvkm_vma *
diff --git a/drivers/gpu/drm/qxl/qxl_ttm.c b/drivers/gpu/drm/qxl/qxl_ttm.c
index 2955f91..28fa56e 100644
--- a/drivers/gpu/drm/qxl/qxl_ttm.c
+++ b/drivers/gpu/drm/qxl/qxl_ttm.c
@@ -394,6 +394,7 @@ static struct ttm_bo_driver qxl_bo_driver = {
 	.verify_access = &qxl_verify_access,
 	.io_mem_reserve = &qxl_ttm_io_mem_reserve,
 	.io_mem_free = &qxl_ttm_io_mem_free,
+	.io_mem_pfn = ttm_bo_default_io_mem_pfn,
 	.move_notify = &qxl_bo_move_notify,
 };
 
diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index 6571384..d07ff84 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -873,6 +873,7 @@ static struct ttm_bo_driver radeon_bo_driver = {
 	.fault_reserve_notify = &radeon_bo_fault_reserve_notify,
 	.io_mem_reserve = &radeon_ttm_io_mem_reserve,
 	.io_mem_free = &radeon_ttm_io_mem_free,
+	.io_mem_pfn = ttm_bo_default_io_mem_pfn,
 };
 
 int radeon_ttm_init(struct radeon_device *rdev)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 750733a..be84e3dc 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -231,7 +231,7 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	 */
 	for (i = 0; i < TTM_BO_VM_NUM_PREFAULT; ++i) {
 		if (bo->mem.bus.is_iomem)
-			pfn = ((bo->mem.bus.base + bo->mem.bus.offset) >> PAGE_SHIFT) + page_offset;
+			pfn = bdev->driver->io_mem_pfn(bo, page_offset);
 		else {
 			page = ttm->pages[page_offset];
 			if (unlikely(!page && i == 0)) {
@@ -324,6 +324,14 @@ static struct ttm_buffer_object *ttm_bo_vm_lookup(struct ttm_bo_device *bdev,
 	return bo;
 }
 
+unsigned long ttm_bo_default_io_mem_pfn(struct ttm_buffer_object *bo,
+					unsigned long page_offset)
+{
+	return ((bo->mem.bus.base + bo->mem.bus.offset) >> PAGE_SHIFT)
+		+ page_offset;
+}
+EXPORT_SYMBOL(ttm_bo_default_io_mem_pfn);
+
 int ttm_bo_mmap(struct file *filp, struct vm_area_struct *vma,
 		struct ttm_bo_device *bdev)
 {
diff --git a/drivers/gpu/drm/virtio/virtgpu_ttm.c b/drivers/gpu/drm/virtio/virtgpu_ttm.c
index a8875a7..8b76bf9 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ttm.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ttm.c
@@ -432,6 +432,7 @@ static struct ttm_bo_driver virtio_gpu_bo_driver = {
 	.verify_access = &virtio_gpu_verify_access,
 	.io_mem_reserve = &virtio_gpu_ttm_io_mem_reserve,
 	.io_mem_free = &virtio_gpu_ttm_io_mem_free,
+	.io_mem_pfn = ttm_bo_default_io_mem_pfn,
 	.move_notify = &virtio_gpu_bo_move_notify,
 	.swap_notify = &virtio_gpu_bo_swap_notify,
 };
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c
index 1de9669..ba2fa7b 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c
@@ -859,4 +859,5 @@ struct ttm_bo_driver vmw_bo_driver = {
 	.fault_reserve_notify = &vmw_ttm_fault_reserve_notify,
 	.io_mem_reserve = &vmw_ttm_io_mem_reserve,
 	.io_mem_free = &vmw_ttm_io_mem_free,
+	.io_mem_pfn = ttm_bo_default_io_mem_pfn,
 };
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 2d0f63e..3b302a5 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -724,6 +724,17 @@ extern int ttm_fbdev_mmap(struct vm_area_struct *vma,
 			  struct ttm_buffer_object *bo);
 
 /**
+ * ttm_bo_default_iomem_pfn - get a pfn for a page offset
+ *
+ * @bo: the BO we need to look up the pfn for
+ * @page_offset: offset inside the BO to look up.
+ *
+ * Calculate the PFN for iomem based mappings during page fault
+ */
+unsigned long ttm_bo_default_io_mem_pfn(struct ttm_buffer_object *bo,
+				        unsigned long page_offset);
+
+/**
  * ttm_bo_mmap - mmap out of the ttm device address space.
  *
  * @filp:      filp as input from the mmap method.
diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
index 7777d14..cb5072a 100644
--- a/include/drm/ttm/ttm_bo_driver.h
+++ b/include/drm/ttm/ttm_bo_driver.h
@@ -462,6 +462,15 @@ struct ttm_bo_driver {
 			      struct ttm_mem_reg *mem);
 	void (*io_mem_free)(struct ttm_bo_device *bdev,
 			    struct ttm_mem_reg *mem);
+
+	/**
+	 * Return the pfn for a given page_offset inside the BO.
+	 *
+	 * @bo: the BO to look up the pfn for
+	 * @page_offset: the offset to look up
+	 */
+	unsigned long (*io_mem_pfn)(struct ttm_buffer_object *bo,
+				    unsigned long page_offset);
 };
 
 /**
