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

[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.

>
> 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);
>