Re: [PATCH v7 3/3] drm/fence: add out-fences support

[Gustavo Padovan]

2016-11-08 Daniel Vetter <daniel@xxxxxxxx>:

> On Tue, Nov 08, 2016 at 03:54:50PM +0900, Gustavo Padovan wrote:
> > From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> > 
> > Support DRM out-fences by creating a sync_file with a fence for each CRTC
> > that sets the OUT_FENCE_PTR property.
> > 
> > We use the out_fence pointer received in the OUT_FENCE_PTR prop to send
> > the sync_file fd back to userspace.
> > 
> > The sync_file and fd are allocated/created before commit, but the
> > fd_install operation only happens after we know that commit succeed.
> > 
> > v2: Comment by Rob Clark:
> > 	- Squash commit that adds DRM_MODE_ATOMIC_OUT_FENCE flag here.
> > 
> >     Comment by Daniel Vetter:
> > 	- Add clean up code for out_fences
> > 
> > v3: Comments by Daniel Vetter:
> > 	- create DRM_MODE_ATOMIC_EVENT_MASK
> > 	- userspace should fill out_fences_ptr with the crtc_ids for which
> > 	it wants fences back.
> > 
> > v4: Create OUT_FENCE_PTR properties and remove old approach.
> > 
> > v5: Comments by Brian Starkey:
> > 	- Remove extra fence_get() in atomic_ioctl()
> > 	- Check ret before iterating on the crtc_state
> > 	- check ret before fd_install
> > 	- set fence_state to NULL at the beginning
> > 	- check fence_state->out_fence_ptr before put_user()
> > 	- change order of fput() and put_unused_fd() on failure
> > 
> >      - Add access_ok() check to the out_fence_ptr received
> >      - Rebase after fence -> dma_fence rename
> >      - Store out_fence_ptr in the drm_atomic_state
> >      - Split crtc_setup_out_fence()
> >      - return -1 as out_fence with TEST_ONLY flag
> > 
> > v6: Comments by Daniel Vetter
> > 	- Add prepare/unprepare_crtc_signaling()
> > 	- move struct drm_out_fence_state to drm_atomic.c
> > 	- mark get_crtc_fence() as static
> > 
> >     Comments by Brian Starkey
> > 	- proper set fence_ptr fence_state array
> > 	- isolate fence_idx increment
> > 
> >     - improve error handling
> > 
> > Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> 
> Found a bunch more nitpicks, and wishlist items for igt coverage.

Thank you, I've collected the list of the igt tests and will work on
them.


> -Daniel
> 
> > ---
> >  drivers/gpu/drm/drm_atomic.c | 233 +++++++++++++++++++++++++++++++++++--------
> >  drivers/gpu/drm/drm_crtc.c   |   8 ++
> >  include/drm/drm_atomic.h     |   1 +
> >  include/drm/drm_crtc.h       |   7 +-
> >  4 files changed, 206 insertions(+), 43 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index d1ae463..9a7d84c 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -289,6 +289,25 @@ drm_atomic_get_crtc_state(struct drm_atomic_state *state,
> >  }
> >  EXPORT_SYMBOL(drm_atomic_get_crtc_state);
> >  
> > +static void
> > +drm_atomic_set_out_fence_for_crtc(struct drm_atomic_state *state,
> > +				  struct drm_crtc *crtc, u64 __user *fence_ptr)
> > +{
> > +	state->crtcs[drm_crtc_index(crtc)].out_fence_ptr = fence_ptr;
> > +}
> > +
> > +static u64 __user *
> > +drm_atomic_get_out_fence_for_crtc(struct drm_atomic_state *state,
> > +			     struct drm_crtc *crtc)
> 
> Since these two are static I'd drop the long prefix to make the code
> easier to read.
> 
> > +{
> > +	u64 __user *fence_ptr;
> > +
> > +	fence_ptr = state->crtcs[drm_crtc_index(crtc)].out_fence_ptr;
> > +	state->crtcs[drm_crtc_index(crtc)].out_fence_ptr = NULL;
> > +
> > +	return fence_ptr;
> > +}
> > +
> >  /**
> >   * drm_atomic_set_mode_for_crtc - set mode for CRTC
> >   * @state: the CRTC whose incoming state to update
> > @@ -490,6 +509,12 @@ int drm_atomic_crtc_set_property(struct drm_crtc *crtc,
> >  					&replaced);
> >  		state->color_mgmt_changed |= replaced;
> >  		return ret;
> > +	} else if (property == config->prop_out_fence_ptr) {
> > +		uint64_t __user *fence_ptr = u64_to_user_ptr(val);
> 
> Don't we need to filter out NULL/0 here like we filter out -1 for the
> in-fences? Just in case some userspace samples/restores all properties.
> 
> Sounds like an igt is missing for this ...
> 
> Maybe we even need a special igt which samples _all_ current atomic
> properties, and then does an atomic commit which changes none of them
> (without setting the ALLOW_MODESET flag ofc). That /should/ work, and
> would catch such bugs in the future.
> 
> > +		if (!access_ok(VERIFY_WRITE, fence_ptr, sizeof(*fence_ptr)))
> > +			return -EFAULT;
> 
> Same comment about igt coverage I made for patch 1, but with
> s/in-fence/out-fence/, and s/~0ULL/8/. I picked 8 as an invalid address !=
> NULL.
> 
> And the testcase need to cover all possible combinations of output event
> generation, i.e. out-fence, event and out-fence+event. So 3x3=9 testcases
> for this I think.

out-fence and event. so 2x2=4 ;)

> 
> > +
> > +		drm_atomic_set_out_fence_for_crtc(state->state, crtc, fence_ptr);
> >  	} else if (crtc->funcs->atomic_set_property)
> >  		return crtc->funcs->atomic_set_property(crtc, state, property, val);
> >  	else
> > @@ -532,6 +557,8 @@ drm_atomic_crtc_get_property(struct drm_crtc *crtc,
> >  		*val = (state->ctm) ? state->ctm->base.id : 0;
> >  	else if (property == config->gamma_lut_property)
> >  		*val = (state->gamma_lut) ? state->gamma_lut->base.id : 0;
> > +	else if (property == config->prop_out_fence_ptr)
> > +		*val = 0;
> >  	else if (crtc->funcs->atomic_get_property)
> >  		return crtc->funcs->atomic_get_property(crtc, state, property, val);
> >  	else
> > @@ -1506,11 +1533,9 @@ EXPORT_SYMBOL(drm_atomic_nonblocking_commit);
> >   */
> >  
> >  static struct drm_pending_vblank_event *create_vblank_event(
> > -		struct drm_device *dev, struct drm_file *file_priv,
> > -		struct dma_fence *fence, uint64_t user_data)
> > +		struct drm_device *dev, uint64_t user_data)
> >  {
> >  	struct drm_pending_vblank_event *e = NULL;
> > -	int ret;
> >  
> >  	e = kzalloc(sizeof *e, GFP_KERNEL);
> >  	if (!e)
> > @@ -1520,17 +1545,6 @@ static struct drm_pending_vblank_event *create_vblank_event(
> >  	e->event.base.length = sizeof(e->event);
> >  	e->event.user_data = user_data;
> >  
> > -	if (file_priv) {
> > -		ret = drm_event_reserve_init(dev, file_priv, &e->base,
> > -					     &e->event.base);
> > -		if (ret) {
> > -			kfree(e);
> > -			return NULL;
> > -		}
> > -	}
> > -
> > -	e->base.fence = fence;
> > -
> >  	return e;
> >  }
> >  
> > @@ -1635,6 +1649,148 @@ void drm_atomic_clean_old_fb(struct drm_device *dev,
> >  }
> >  EXPORT_SYMBOL(drm_atomic_clean_old_fb);
> >  
> > +static struct dma_fence *get_crtc_fence(struct drm_crtc *crtc,
> > +					struct drm_crtc_state *crtc_state)
> > +{
> > +	struct dma_fence *fence;
> > +
> > +	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
> > +	if (!fence)
> > +		return NULL;
> > +
> > +	dma_fence_init(fence, &drm_crtc_fence_ops, &crtc->fence_lock,
> > +		       crtc->fence_context, ++crtc->fence_seqno);
> > +
> > +	return fence;
> > +}
> > +
> > +struct drm_out_fence_state {
> > +	u64 __user *out_fence_ptr;
> 
> You have a type mess here. The pointer is to an u64, but the value you
> store there is an int. Since we want to avoid fund with 32bit userspace
> vs. 64bit kernel I think it should be an s64 everywhere.
> > +	struct sync_file *sync_file;
> > +	int fd;
> > +};
> > +
> > +static int setup_out_fence(struct drm_out_fence_state *fence_state,
> > +			   struct dma_fence *fence)
> > +{
> > +	fence_state->fd = get_unused_fd_flags(O_CLOEXEC);
> > +	if (fence_state->fd < 0)
> > +		return fence_state->fd;
> > +
> > +	if (put_user(fence_state->fd, fence_state->out_fence_ptr))
> > +		return -EFAULT;
> > +
> > +	fence_state->sync_file = sync_file_create(fence);
> > +	if(!fence_state->sync_file)
> > +		return -ENOMEM;
> > +
> > +	return 0;
> > +}
> > +
> > +static int prepare_crtc_signaling(struct drm_device *dev,
> > +				  struct drm_atomic_state *state,
> > +				  struct drm_mode_atomic *arg,
> > +				  struct drm_file *file_priv,
> > +				  struct drm_out_fence_state *fence_state)
> > +{
> > +	struct drm_crtc *crtc;
> > +	struct drm_crtc_state *crtc_state;
> > +	int i, ret, fence_idx = 0;
> > +
> > +	for_each_crtc_in_state(state, crtc, crtc_state, i) {
> > +		u64 __user *fence_ptr;
> > +
> > +		fence_ptr = drm_atomic_get_out_fence_for_crtc(crtc_state->state,
> > +							      crtc);
> > +
> > +		if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY && fence_ptr) {
> > +			if (put_user(-1, fence_ptr))
> > +				return -EFAULT;
> > +
> > +			continue;
> > +		}
> > +
> > +		if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT || fence_ptr) {
> > +			struct drm_pending_vblank_event *e;
> > +
> > +			e = create_vblank_event(dev, arg->user_data);
> > +			if (!e)
> > +				return -ENOMEM;
> > +
> > +			crtc_state->event = e;
> > +		}
> > +
> > +		if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
> > +			struct drm_pending_vblank_event *e = crtc_state->event;
> > +
> > +			if (!file_priv)
> > +				continue;
> > +
> > +			ret = drm_event_reserve_init(dev, file_priv, &e->base,
> > +						     &e->event.base);
> > +			if (ret) {
> > +				kfree(e);
> > +				crtc_state->event = NULL;
> > +				return ret;
> > +			}
> > +		}
> > +
> > +		if (fence_ptr) {
> > +			struct dma_fence *fence;
> > +
> > +			fence_state[fence_idx].out_fence_ptr = fence_ptr;
> > +
> > +			fence = get_crtc_fence(crtc, crtc_state);
> > +			if (!fence)
> > +				return -ENOMEM;
> > +
> > +			ret = setup_out_fence(&fence_state[fence_idx], fence);
> > +			if (ret) {
> > +				dma_fence_put(fence);
> > +				return ret;
> > +			}
> > +
> > +			fence_idx++;
> > +
> > +			crtc_state->event->base.fence = fence;
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static void unprepare_crtc_signaling(struct drm_device *dev,
> > +				     struct drm_atomic_state *state,
> > +				     struct drm_out_fence_state *fence_state)
> > +{
> > +	struct drm_crtc *crtc;
> > +	struct drm_crtc_state *crtc_state;
> > +	int i;
> > +
> > +	for_each_crtc_in_state(state, crtc, crtc_state, i) {
> > +		/*
> > +		 * TEST_ONLY and PAGE_FLIP_EVENT are mutually
> > +		 * exclusive, if they weren't, this code should be
> > +		 * called on success for TEST_ONLY too.
> > +		 */
> > +		if (crtc_state->event)
> > +			drm_event_cancel_free(dev,
> > +					      &crtc_state->event->base);
> > +	}
> > +
> > +	for (i = 0; fence_state[i].out_fence_ptr; i++) {
> 
> This goes boom if you have fences set for every crtc, because then this
> check will walk past the end of the array and do something undefined. You
> need to manually count how many of these slots are set (and might want to
> switch to a krealloc pattern while at it). Sounds like it needs an igt.

On the fd_install loop I was also checking for i <
dev->mode_config.num_crtcs but forgot to add that here. However having a
num_fences is a better solution, I'll add that.

> 
> > +		if (fence_state[i].sync_file)
> > +			fput(fence_state[i].sync_file->file);
> > +		if (fence_state[i].fd >= 0)
> > +			put_unused_fd(fence_state[i].fd);
> > +
> > +		/* If this fails log error to the user */
> > +		if (fence_state[i].out_fence_ptr &&
> > +		    put_user(-1, fence_state[i].out_fence_ptr))
> > +			DRM_INFO("Couldn't clear out_fence_ptr\n");
> 
> Userspace can provoke this (race an munmap against an atomic ioctl), and
> userspace is not allowed to spam dmesg. Please degrade to
> DRM_DEBUG_ATOMIC.
> 
> > +	}
> > +}
> > +
> >  int drm_mode_atomic_ioctl(struct drm_device *dev,
> >  			  void *data, struct drm_file *file_priv)
> >  {
> > @@ -1647,8 +1803,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
> >  	struct drm_atomic_state *state;
> >  	struct drm_modeset_acquire_ctx ctx;
> >  	struct drm_plane *plane;
> > -	struct drm_crtc *crtc;
> > -	struct drm_crtc_state *crtc_state;
> > +	struct drm_out_fence_state *fence_state = NULL;
> >  	unsigned plane_mask;
> >  	int ret = 0;
> >  	unsigned int i, j;
> > @@ -1766,21 +1921,18 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
> >  		drm_mode_object_unreference(obj);
> >  	}
> >  
> > -	if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
> > -		for_each_crtc_in_state(state, crtc, crtc_state, i) {
> > -			struct drm_pending_vblank_event *e;
> > -
> > -			e = create_vblank_event(dev, file_priv, NULL,
> > -						arg->user_data);
> > -			if (!e) {
> > -				ret = -ENOMEM;
> > -				goto out;
> > -			}
> > -
> > -			crtc_state->event = e;
> > -		}
> > +	fence_state = kzalloc(dev->mode_config.num_crtc * sizeof(*fence_state),
> > +			      GFP_KERNEL);
> > +	if (!fence_state) {
> > +		ret = -ENOMEM;
> > +		goto out;
> >  	}
> >  
> > +	ret = prepare_crtc_signaling(dev, state, arg, file_priv,
> > +					  fence_state);
> 
> Personally I'd pass &fence_state here and only krealloc within prepare if
> needed. And as mentioned you need an &num_fences here too.
> 
> > +	if (ret)
> > +		goto out;
> > +
> >  	if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) {
> >  		/*
> >  		 * Unlike commit, check_only does not clean up state.
> > @@ -1793,23 +1945,20 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
> >  		ret = drm_atomic_commit(state);
> >  	}
> >  
> > +	if (ret)
> > +		goto out;
> > +
> > +	for (i = 0; fence_state[i].sync_file && i < dev->mode_config.num_crtc;
> > +	     i++)
> > +		fd_install(fence_state[i].fd, fence_state[i].sync_file->file);
> > +
> >  out:
> >  	drm_atomic_clean_old_fb(dev, plane_mask, ret);
> >  
> > -	if (ret && arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
> > -		/*
> > -		 * TEST_ONLY and PAGE_FLIP_EVENT are mutually exclusive,
> > -		 * if they weren't, this code should be called on success
> > -		 * for TEST_ONLY too.
> > -		 */
> > -
> > -		for_each_crtc_in_state(state, crtc, crtc_state, i) {
> > -			if (!crtc_state->event)
> > -				continue;
> > +	if (ret && fence_state)
> > +		unprepare_crtc_signaling(dev, state, fence_state);
> 
> I'm tempted to rework this to:
> 
> 	complete_crtc_signalling(dev, state, fence_state, ret)
> 
> and push the check for fence_state == NULL into it. And also use ret to
> decide whether we need to clean up, or fd_install the fence. That way
> everything is in one place. That would also tidy up the control flow a
> bit. And s/unprepare/complete since it wouldn't just be the error path
> cleanup any more.

Yes, this is a lot more cleaner. Thanks for the suggestion.

Gustavo