[PATCH v2] drm/ttm: update bulk move object of ghost BO

[Matthew Auld]

On Tue, 6 Sept 2022 at 09:54, Christian König <christian.koenig at amd.com> wrote:
>
> Am 06.09.22 um 10:46 schrieb ZhenGuo Yin:
> > [Why]
> > Ghost BO is released with non-empty bulk move object. There is a
> > warning trace:
> > WARNING: CPU: 19 PID: 1582 at ttm/ttm_bo.c:366 ttm_bo_release+0x2e1/0x2f0 [amdttm]
> > Call Trace:
> >    amddma_resv_reserve_fences+0x10d/0x1f0 [amdkcl]
> >    amdttm_bo_put+0x28/0x30 [amdttm]
> >    amdttm_bo_move_accel_cleanup+0x126/0x200 [amdttm]
> >    amdgpu_bo_move+0x1a8/0x770 [amdgpu]
> >    ttm_bo_handle_move_mem+0xb0/0x140 [amdttm]
> >    amdttm_bo_validate+0xbf/0x100 [amdttm]
> >
> > [How]
> > The resource of ghost BO should be moved to LRU directly, instead of
> > using bulk move. The bulk move object of ghost BO should set to NULL
> > before function ttm_bo_move_to_lru_tail_unlocked.
> >
> > v2: set bulk move to NULL manually if no resource associated with ghost BO
> >
> > Fixed: 5b951e487fd6bf5f ("drm/ttm: fix bulk move handling v2")
> > Signed-off-by: ZhenGuo Yin <zhenguo.yin at amd.com>
>
> Reviewed-by: Christian König <christian.koenig at amd.com>
>
> Going to push that to drm-misc-fixes in a minute.
>
> Thanks,
> Christian.
>
> > ---
> >   drivers/gpu/drm/ttm/ttm_bo_util.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
> > index 1cbfb00c1d65..57a27847206f 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
> > @@ -239,6 +239,9 @@ static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
> >       if (fbo->base.resource) {
> >               ttm_resource_set_bo(fbo->base.resource, &fbo->base);
> >               bo->resource = NULL;
> > +             ttm_bo_set_bulk_move(&fbo->base, NULL);

This appears to blow up quite badly in i915. See here for an example trace:
https://gitlab.freedesktop.org/drm/intel/-/issues/6744

Do you know if amdgpu is also hitting this, or is this somehow i915 specific?

> > +     } else {
> > +             fbo->base.bulk_move = NULL;
> >       }
> >
> >       dma_resv_init(&fbo->base.base._resv);
>