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

[Matthew Auld]

On Wed, 29 Sept 2021 at 13:01, Christian König <christian.koenig at amd.com> wrote:
>
> 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.

Version which should apply to drm-misc-next:
https://patchwork.freedesktop.org/series/95219/

>
> 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);
>