[PATCH v3 06/12] drm/ttm: add TTM_PAGE_FLAG_EXTERNAL_MAPPABLE

[Matthew Auld]

In commit:

commit 667a50db0477d47fdff01c666f5ee1ce26b5264c
Author: Thomas Hellstrom <thellstrom at vmware.com>
Date:   Fri Jan 3 11:17:18 2014 +0100

    drm/ttm: Refuse to fault (prime-) imported pages

we introduced the restriction that imported pages should not be directly
mappable through TTM(this also extends to userptr). In the next patch we
want to introduce a shmem_tt backend, which should follow all the
existing rules with TTM_PAGE_FLAG_EXTERNAL, since it will need to handle
swapping itself, but with the above mapping restriction lifted.

Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Cc: Christian König <christian.koenig at amd.com>
---
 drivers/gpu/drm/ttm/ttm_bo_vm.c | 6 ++++--
 include/drm/ttm/ttm_tt.h        | 7 +++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 708390588c7c..fd6e18f12f50 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -163,8 +163,10 @@ vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
 	 * (if at all) by redirecting mmap to the exporter.
 	 */
 	if (bo->ttm && (bo->ttm->page_flags & TTM_PAGE_FLAG_EXTERNAL)) {
-		dma_resv_unlock(bo->base.resv);
-		return VM_FAULT_SIGBUS;
+		if (!(bo->ttm->page_flags & TTM_PAGE_FLAG_EXTERNAL_MAPPABLE)) {
+			dma_resv_unlock(bo->base.resv);
+			return VM_FAULT_SIGBUS;
+		}
 	}
 
 	return 0;
diff --git a/include/drm/ttm/ttm_tt.h b/include/drm/ttm/ttm_tt.h
index 7f54a83c95ef..800c9edb3e10 100644
--- a/include/drm/ttm/ttm_tt.h
+++ b/include/drm/ttm/ttm_tt.h
@@ -66,11 +66,18 @@ struct ttm_tt {
 	 * Note that enum ttm_bo_type.ttm_bo_type_sg objects will always enable
 	 * this flag.
 	 *
+	 * TTM_PAGE_FLAG_EXTERNAL_MAPPABLE: Same behaviour as
+	 * TTM_PAGE_FLAG_EXTERNAL, but with the reduced restriction that it is
+	 * still valid to use TTM to map the pages directly. This is useful when
+	 * implementing a ttm_tt backend which still allocates driver owned
+	 * pages underneath(say with shmem).
+	 *
 	 * TTM_PAGE_FLAG_PRIV_POPULATED: TTM internal only. DO NOT USE.
 	 */
 #define TTM_PAGE_FLAG_SWAPPED		(1 << 0)
 #define TTM_PAGE_FLAG_ZERO_ALLOC	(1 << 1)
 #define TTM_PAGE_FLAG_EXTERNAL		(1 << 2)
+#define TTM_PAGE_FLAG_EXTERNAL_MAPPABLE	(1 << 3 | TTM_PAGE_FLAG_EXTERNAL)
 
 #define TTM_PAGE_FLAG_PRIV_POPULATED	(1 << 31)
 	uint32_t page_flags;
-- 
2.26.3