[Intel-gfx] [PATCH v5 01/13] drm/ttm: stop calling tt_swapin in vm_access

[Christian König]

Am 27.09.21 um 18:14 schrieb Matthew Auld:
> On Mon, 27 Sept 2021 at 12:47, Christian König <christian.koenig at amd.com> 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 at amd.com>
>>> 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 at intel.com>
>>> Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
>>> Cc: Christian König <christian.koenig at amd.com>
>>> Reviewed-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
>>> Reviewed-by: Christian König <christian.koenig at amd.com>
>>> ---
>>>    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);