Re: [PATCH v5 01/13] drm/ttm: stop calling tt_swapin in vm_access

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Am 27.09.21 um 18:14 schrieb Matthew Auld:
On Mon, 27 Sept 2021 at 12:47, Christian König <christian.koenig@xxxxxxx> wrote:
Any objections that I just push patches 1-7 to drm-misc-next?
Please go ahead Christian. Thanks.

Well I've pushed patches #1-#4 because #5 won't apply on current drm-misc-next (some conflict in i915).

Could you rebase this an/or request backmerging of drm-next into drm-misc-next when potential i915 prerequisites have landed there.

Thanks,
Christian.


Christian.

Am 27.09.21 um 13:41 schrieb Matthew Auld:
In commit:

commit 09ac4fcb3f255e9225967c75f5893325c116cdbe
Author: Felix Kuehling <Felix.Kuehling@xxxxxxx>
Date:   Thu Jul 13 17:01:16 2017 -0400

      drm/ttm: Implement vm_operations_struct.access v2

we added the vm_access hook, where we also directly call tt_swapin for
some reason. If something is swapped-out then the ttm_tt must also be
unpopulated, and since access_kmap should also call tt_populate, if
needed, then swapping-in will already be handled there.

If anything, calling tt_swapin directly here would likely always fail
since the tt->pages won't yet be populated, or worse since the tt->pages
array is never actually cleared in unpopulate this might lead to a nasty
uaf.

Fixes: 09ac4fcb3f25 ("drm/ttm: Implement vm_operations_struct.access v2")
Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Reviewed-by: Christian König <christian.koenig@xxxxxxx>
---
   drivers/gpu/drm/ttm/ttm_bo_vm.c | 5 -----
   1 file changed, 5 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index f56be5bc0861..5b9b7fd01a69 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -519,11 +519,6 @@ int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,

       switch (bo->resource->mem_type) {
       case TTM_PL_SYSTEM:
-             if (unlikely(bo->ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)) {
-                     ret = ttm_tt_swapin(bo->ttm);
-                     if (unlikely(ret != 0))
-                             return ret;
-             }
               fallthrough;
       case TTM_PL_TT:
               ret = ttm_bo_vm_access_kmap(bo, offset, buf, len, write);




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