Re: [PATCH 3/7] drm/amd/display: Avoid using unvalidated tiling_flags and tmz_surface in prepare_planes

["Kazlauskas, Nicholas" <nicholas.kazlauskas@xxxxxxx>]

On 2020-08-07 4:30 a.m., daniel@xxxxxxxx wrote:
> On Thu, Jul 30, 2020 at 04:36:38PM -0400, Nicholas Kazlauskas wrote:
> > [Why]
> > We're racing with userspace as the flags could potentially change
> > from when we acquired and validated them in commit_check.
>
> Uh ... I didn't know these could change. I think my comments on Bas'
> series are even more relevant now. I think long term would be best to bake
> these flags in at addfb time when modifiers aren't set. And otherwise
> always use the modifiers flag, and completely ignore the legacy flags
> here.
> -Daniel

There's a set tiling/mod flags IOCTL that can be called after addfb 
happens, so unless there's some sort of driver magic preventing this 
from working when it's already been pinned for scanout then I don't see 
anything stopping this from happening.

I still need to review the modifiers series in a little more detail but 
that looks like a good approach to fixing these kind of issues.

Regards,
Nicholas Kazlauskas

> > [How]
> > We unfortunately can't drop this function in its entirety from
> > prepare_planes since we don't know the afb->address at commit_check
> > time yet.
> >
> > So instead of querying new tiling_flags and tmz_surface use the ones
> > from the plane_state directly.
> >
> > While we're at it, also update the force_disable_dcc option based
> > on the state from atomic check.
> >
> > Cc: Bhawanpreet Lakha <Bhawanpreet.Lakha@xxxxxxx>
> > Cc: Rodrigo Siqueira <Rodrigo.Siqueira@xxxxxxx>
> > Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx>
> > ---
> >   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 36 ++++++++++---------
> >   1 file changed, 19 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > index bf1881bd492c..f78c09c9585e 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > @@ -5794,14 +5794,8 @@ static int dm_plane_helper_prepare_fb(struct drm_plane *plane,
> >   	struct list_head list;
> >   	struct ttm_validate_buffer tv;
> >   	struct ww_acquire_ctx ticket;
> > -	uint64_t tiling_flags;
> >   	uint32_t domain;
> >   	int r;
> > -	bool tmz_surface = false;
> > -	bool force_disable_dcc = false;
> > -
> > -	dm_plane_state_old = to_dm_plane_state(plane->state);
> > -	dm_plane_state_new = to_dm_plane_state(new_state);
> >   
> >   	if (!new_state->fb) {
> >   		DRM_DEBUG_DRIVER("No FB bound\n");
> > @@ -5845,27 +5839,35 @@ static int dm_plane_helper_prepare_fb(struct drm_plane *plane,
> >   		return r;
> >   	}
> >   
> > -	amdgpu_bo_get_tiling_flags(rbo, &tiling_flags);
> > -
> > -	tmz_surface = amdgpu_bo_encrypted(rbo);
> > -
> >   	ttm_eu_backoff_reservation(&ticket, &list);
> >   
> >   	afb->address = amdgpu_bo_gpu_offset(rbo);
> >   
> >   	amdgpu_bo_ref(rbo);
> >   
> > +	/**
> > +	 * We don't do surface updates on planes that have been newly created,
> > +	 * but we also don't have the afb->address during atomic check.
> > +	 *
> > +	 * Fill in buffer attributes depending on the address here, but only on
> > +	 * newly created planes since they're not being used by DC yet and this
> > +	 * won't modify global state.
> > +	 */
> > +	dm_plane_state_old = to_dm_plane_state(plane->state);
> > +	dm_plane_state_new = to_dm_plane_state(new_state);
> > +
> >   	if (dm_plane_state_new->dc_state &&
> > -			dm_plane_state_old->dc_state != dm_plane_state_new->dc_state) {
> > -		struct dc_plane_state *plane_state = dm_plane_state_new->dc_state;
> > +	    dm_plane_state_old->dc_state != dm_plane_state_new->dc_state) {
> > +		struct dc_plane_state *plane_state =
> > +			dm_plane_state_new->dc_state;
> > +		bool force_disable_dcc = !plane_state->dcc.enable;
> >   
> > -		force_disable_dcc = adev->asic_type == CHIP_RAVEN && adev->in_suspend;
> >   		fill_plane_buffer_attributes(
> >   			adev, afb, plane_state->format, plane_state->rotation,
> > -			tiling_flags, &plane_state->tiling_info,
> > -			&plane_state->plane_size, &plane_state->dcc,
> > -			&plane_state->address, tmz_surface,
> > -			force_disable_dcc);
> > +			dm_plane_state_new->tiling_flags,
> > +			&plane_state->tiling_info, &plane_state->plane_size,
> > +			&plane_state->dcc, &plane_state->address,
> > +			dm_plane_state_new->tmz_surface, force_disable_dcc);
> >   	}
> >   
> >   	return 0;
> > --
> > 2.25.1
> >
> > _______________________________________________
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> > dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel

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