Am 15.09.21 um 20:59 schrieb Matthew Auld:
In commit:
commit 667a50db0477d47fdff01c666f5ee1ce26b5264c
Author: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
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@xxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
---
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)
That's really bad practice because an "if (!(flags &
TTM_PAGE_FLAG_EXTERNAL_MAPPABLE))" has a different semantics as an "if
(flags & TTM_PAGE_FLAG_EXTERNAL_MAPPABLE)".
Rather add a TTM_PAGE_FLAG_UNMAPPABLE and make sure that it is set as
appropriated.
Regards,
Christian.
#define TTM_PAGE_FLAG_PRIV_POPULATED (1 << 31)
uint32_t page_flags;
