On Thu, Mar 31, 2022 at 10:52:54PM +0300, Ville Syrjälä wrote: > On Thu, Mar 31, 2022 at 09:11:29PM +0200, Daniel Vetter wrote: > > On Thu, Mar 31, 2022 at 06:48:43PM +0300, Ville Syrjälä wrote: > > > On Thu, Mar 31, 2022 at 05:14:29PM +0200, Daniel Vetter wrote: > > > > On Thu, Mar 31, 2022 at 04:25:13PM +0300, Ville Syrjälä wrote: > > > > > On Thu, Mar 31, 2022 at 03:05:45PM +0200, Maxime Ripard wrote: > > > > > > From: Daniel Vetter <daniel.vetter@xxxxxxxx> > > > > > > > > > > > > The stuff never really worked, and leads to lots of fun because it > > > > > > out-of-order frees atomic states. Which upsets KASAN, among other > > > > > > things. > > > > > > > > > > > > For async updates we now have a more solid solution with the > > > > > > ->atomic_async_check and ->atomic_async_commit hooks. Support for that > > > > > > for msm and vc4 landed. nouveau and i915 have their own commit > > > > > > routines, doing something similar. > > > > > > > > > > > > For everyone else it's probably better to remove the use-after-free > > > > > > bug, and encourage folks to use the async support instead. The > > > > > > affected drivers which register a legacy cursor plane and don't either > > > > > > use the new async stuff or their own commit routine are: amdgpu, > > > > > > atmel, mediatek, qxl, rockchip, sti, sun4i, tegra, virtio, and vmwgfx. > > > > > > > > > > > > Inspired by an amdgpu bug report. > > > > > > > > > > > > v2: Drop RFC, I think with amdgpu converted over to use > > > > > > atomic_async_check/commit done in > > > > > > > > > > > > commit 674e78acae0dfb4beb56132e41cbae5b60f7d662 > > > > > > Author: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx> > > > > > > Date: Wed Dec 5 14:59:07 2018 -0500 > > > > > > > > > > > > drm/amd/display: Add fast path for cursor plane updates > > > > > > > > > > > > we don't have any driver anymore where we have userspace expecting > > > > > > solid legacy cursor support _and_ they are using the atomic helpers in > > > > > > their fully glory. So we can retire this. > > > > > > > > > > > > v3: Paper over msm and i915 regression. The complete_all is the only > > > > > > thing missing afaict. > > > > > > > > > > > > v4: Rebased on recent kernel, added extra link for vc4 bug. > > > > > > > > > > > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=199425 > > > > > > Link: https://lore.kernel.org/all/20220221134155.125447-9-maxime@xxxxxxxxxx/ > > > > > > Cc: mikita.lipski@xxxxxxx > > > > > > Cc: Michel Dänzer <michel@xxxxxxxxxxx> > > > > > > Cc: harry.wentland@xxxxxxx > > > > > > Cc: Rob Clark <robdclark@xxxxxxxxx> > > > > > > Cc: "Kazlauskas, Nicholas" <nicholas.kazlauskas@xxxxxxx> > > > > > > Tested-by: Maxime Ripard <maxime@xxxxxxxxxx> > > > > > > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > > > > > > Signed-off-by: Maxime Ripard <maxime@xxxxxxxxxx> > > > > > > --- > > > > > > drivers/gpu/drm/drm_atomic_helper.c | 13 ------------- > > > > > > drivers/gpu/drm/i915/display/intel_display.c | 13 +++++++++++++ > > > > > > drivers/gpu/drm/msm/msm_atomic.c | 2 ++ > > > > > > 3 files changed, 15 insertions(+), 13 deletions(-) > > > > > > > > > > > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c > > > > > > index 9603193d2fa1..a2899af82b4a 100644 > > > > > > --- a/drivers/gpu/drm/drm_atomic_helper.c > > > > > > +++ b/drivers/gpu/drm/drm_atomic_helper.c > > > > > > @@ -1498,13 +1498,6 @@ drm_atomic_helper_wait_for_vblanks(struct drm_device *dev, > > > > > > int i, ret; > > > > > > unsigned int crtc_mask = 0; > > > > > > > > > > > > - /* > > > > > > - * Legacy cursor ioctls are completely unsynced, and userspace > > > > > > - * relies on that (by doing tons of cursor updates). > > > > > > - */ > > > > > > - if (old_state->legacy_cursor_update) > > > > > > - return; > > > > > > - > > > > > > for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) { > > > > > > if (!new_crtc_state->active) > > > > > > continue; > > > > > > @@ -2135,12 +2128,6 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state, > > > > > > continue; > > > > > > } > > > > > > > > > > > > - /* Legacy cursor updates are fully unsynced. */ > > > > > > - if (state->legacy_cursor_update) { > > > > > > - complete_all(&commit->flip_done); > > > > > > - continue; > > > > > > - } > > > > > > - > > > > > > if (!new_crtc_state->event) { > > > > > > commit->event = kzalloc(sizeof(*commit->event), > > > > > > GFP_KERNEL); > > > > > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c > > > > > > index bf7ce684dd8e..bde32f5a33cb 100644 > > > > > > --- a/drivers/gpu/drm/i915/display/intel_display.c > > > > > > +++ b/drivers/gpu/drm/i915/display/intel_display.c > > > > > > @@ -8855,6 +8855,19 @@ static int intel_atomic_commit(struct drm_device *dev, > > > > > > state->base.legacy_cursor_update = false; > > > > > > } > > > > > > > > > > > > + /* > > > > > > + * FIXME: Cut over to (async) commit helpers instead of hand-rolling > > > > > > + * everything. > > > > > > + */ > > > > > > > > > > Intel cursors can't even do async updates so this is rather > > > > > nonsensical. What we need is some kind of reasonable mailbox > > > > > support. > > > > > > > > This is not the async plane update you're thinking of. i915 really should > > > > switch over more to atomic helpers. > > > > > > The comment should be clarified then. As is I have no real idea > > > what it's trying to say. > > > > Use drm_atomic_commit and only overwrite atomic_commit_tail. > > You mean drm_atomic_helper_commit() I suppose? > > > But I'm not > > really clear why the comment isn't clear - i915 is the only driver not > > using them, maybe should start to take a look when they're so unfamiliar > > :-P > > There are a lot of problems with that: > - no uapi/hw state split so if there's anything that looks > at the state it's very likely going to get things wrong > - it doesn't know anything about i915's own state objects > - uses wrong workqueues > > Those are the ones that immediately came to mind when I looked > at it. Probably I missed some others as well. Yeah and we could have fixed them in the shared code, and 5+ years ago I even had patches, but i915 gem team had the idea they know better. That part really needs to be fixed, and if that means redoing a bunch of display work because display team didn't push back on gem team reinventing all the wheels ... tough luck. I suggest you get started. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
