Am 21.09.21 um 13:37 schrieb Thomas Hellström:
HI, Christian,
On Tue, 2021-09-21 at 13:28 +0200, Christian König wrote:
Am 21.09.21 um 13:01 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.
Sounds like you completely misunderstand what that is good for.
This is for debugger attaching to a process and peek/poke into the
VMA
and completely unrelated to kmap.
I think what Matthew is saying is that there is a fallthrough to
TTM_PL_TT which calls
ttm_bo_vm_access_kmap
Ah, good point. Now that makes much more sense.
which calls
ttm_tt_populate().
So from my pow, unless there are other concerns, this is
Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
In that case the patch is Reviewed-by: Christian König
<christian.koenig@xxxxxxx> as well.
When this is gone we can also make ttm_tt_swapin() static since that
here is the only user.
And BTW replacing the switch/case with a check for use_tt in the
resource_manager is probably a good idea as well.
Regards,
Christian.
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.
That's indeed true, but we just need to unconditionally call
ttm_tt_populate() here instead.
Regards,
Christian.
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>
---
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);
