Re: [PATCH v6 6/6] drm/fence: add out-fences support

[Daniel Vetter]

On Thu, Oct 27, 2016 at 05:37:11PM -0200, 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
> 
> Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>

I think this looks good. Again I'll wait with full in-depth review of all
the input validation until the igt shows up, but I think we're mostly
covereed. A few smaller comments for polish below.
-Daniel

> ---
>  drivers/gpu/drm/drm_atomic.c | 199 ++++++++++++++++++++++++++++++++++++-------
>  drivers/gpu/drm/drm_crtc.c   |   8 ++
>  include/drm/drm_atomic.h     |   1 +
>  include/drm/drm_crtc.h       |  17 ++++
>  4 files changed, 196 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 28d9366..9b70a27 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -290,6 +290,46 @@ drm_atomic_get_crtc_state(struct drm_atomic_state *state,
>  EXPORT_SYMBOL(drm_atomic_get_crtc_state);
>  
>  /**
> + * drm_atomic_set_out_fence_for_crtc - set CRTC out fence pointer
> + * @state: global atomic state object
> + * @crtc: crtc to set the out fence pointer
> + * @fence_ptr: the userspace pointer to user
> + *
> + * This function stores the out fence pointer in the atomic 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;
> +}
> +
> +/**
> + * drm_atomic_get_out_fence_for_crtc - get CRTC out fence pointer
> + * @state: global atomic state object
> + * @crtc: crtc to set the out fence pointer
> + *
> + * Get the user pointer that should be used for to store the out fence fd.
> + * This function should be called only once per atomic state as it clears
> + * the out_fence_ptr store there to prevent drivers to access them.
> + *
> + * Returns:
> + *
> + * The out fence user pointer.
> + */

We don't document non-driver-visble functions and structs, and especially
static functions should be self explanatory. I feel bad for your effort in
typing kernel-doc here :(

> +static u64 __user *
> +drm_atomic_get_out_fence_for_crtc(struct drm_atomic_state *state,
> +			     struct drm_crtc *crtc)
> +{
> +	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
>   * @mode: kernel-internal mode to use for the CRTC, or NULL to disable
> @@ -490,6 +530,12 @@ 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);
> +		if (!access_ok(VERIFY_WRITE, fence_ptr, sizeof(*fence_ptr)))
> +			return -EFAULT;
> +
> +		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 +578,8 @@ 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 +1554,9 @@ 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 +1566,6 @@ 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 +1670,38 @@ void drm_atomic_clean_old_fb(struct drm_device *dev,
>  }
>  EXPORT_SYMBOL(drm_atomic_clean_old_fb);
>  
> +struct dma_fence *get_crtc_fence(struct drm_crtc *crtc,
> +				 struct drm_crtc_state *crtc_state)

static?

> +{
> +	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;
> +}
> +
> +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;
> +}
> +
>  int drm_mode_atomic_ioctl(struct drm_device *dev,
>  			  void *data, struct drm_file *file_priv)
>  {
> @@ -1649,9 +1716,10 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  	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;
> +	unsigned int i, j, fence_idx = 0;
>  
>  	/* disallow for drivers not supporting atomic: */
>  	if (!drm_core_check_feature(dev, DRIVER_ATOMIC))
> @@ -1766,13 +1834,33 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  		drm_mode_object_unreference(obj);
>  	}
>  
> +	fence_state = kcalloc(dev->mode_config.num_crtc, sizeof(*fence_state),
> +			      GFP_KERNEL);
> +	if (!fence_state) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
>  
> -	if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
> -		for_each_crtc_in_state(state, crtc, crtc_state, i) {
> +	for_each_crtc_in_state(state, crtc, crtc_state, i) {
> +
> +		fence_state->out_fence_ptr =
> +			drm_atomic_get_out_fence_for_crtc(crtc_state->state, crtc);
> +
> +		if (fence_state->out_fence_ptr &&
> +		    (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY)) {
> +			if (put_user(-1, fence_state->out_fence_ptr)) {
> +				ret = -EFAULT;
> +				goto out;
> +			}
> +
> +			continue;
> +		}
> +
> +		if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT ||
> +		    fence_state->out_fence_ptr) {
>  			struct drm_pending_vblank_event *e;
>  
> -			e = create_vblank_event(dev, file_priv, NULL,
> -						arg->user_data);
> +			e = create_vblank_event(dev, arg->user_data);
>  			if (!e) {
>  				ret = -ENOMEM;
>  				goto out;
> @@ -1780,6 +1868,39 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  
>  			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;
> +				goto out;
> +			}
> +		}
> +
> +		if (fence_state->out_fence_ptr) {
> +			struct dma_fence *fence;
> +
> +			fence = get_crtc_fence(crtc, crtc_state);
> +			if (!fence) {
> +				ret = -ENOMEM;
> +				goto out;
> +			}
> +
> +			ret = setup_out_fence(&fence_state[fence_idx++], fence);
> +			if (ret) {
> +				dma_fence_put(fence);
> +				goto out;
> +			}
> +
> +			crtc_state->event->base.fence = fence;
> +		}

I think the entire above loop body should be extracted into a helper
function, like prepare_crtc_signalling or similar. drm_mode_atomic_ioctl
is huge already as-is ;-)

>  	}
>  
>  	if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) {
> @@ -1794,24 +1915,44 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
>  		ret = drm_atomic_commit(state);
>  	}
>  
> +	if (ret)
> +		goto out;
> +
> +	for (i = 0; i < fence_idx; 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.
> -		 */
> -
> +	if (ret) {
>  		for_each_crtc_in_state(state, crtc, crtc_state, i) {
> -			if (!crtc_state->event)
> -				continue;
> +			/*
> +			 * 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);
> +		}
>  
> -			drm_event_cancel_free(dev, &crtc_state->event->base);
> +		if (fence_state) {
> +			for (i = 0; i < fence_idx; i++) {
> +				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");
> +			}
>  		}

Same here, for symmetry maybe a unprepare_crtc_signalling or so, to make
it clear that this undoes what the first one set up.

>  	}
>  
> +	kfree(fence_state);
> +
>  	if (ret == -EDEADLK) {
>  		drm_atomic_state_clear(state);
>  		drm_modeset_backoff(&ctx);
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index e2a06c8..a18d81b 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -274,6 +274,8 @@ int drm_crtc_init_with_planes(struct drm_device *dev, struct drm_crtc *crtc,
>  	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
>  		drm_object_attach_property(&crtc->base, config->prop_active, 0);
>  		drm_object_attach_property(&crtc->base, config->prop_mode_id, 0);
> +		drm_object_attach_property(&crtc->base,
> +					   config->prop_out_fence_ptr, 0);
>  	}
>  
>  	return 0;
> @@ -434,6 +436,12 @@ static int drm_mode_create_standard_properties(struct drm_device *dev)
>  		return -ENOMEM;
>  	dev->mode_config.prop_in_fence_fd = prop;
>  
> +	prop = drm_property_create_range(dev, DRM_MODE_PROP_ATOMIC,
> +			"OUT_FENCE_PTR", 0, U64_MAX);
> +	if (!prop)
> +		return -ENOMEM;
> +	dev->mode_config.prop_out_fence_ptr = prop;
> +
>  	prop = drm_property_create_object(dev, DRM_MODE_PROP_ATOMIC,
>  			"CRTC_ID", DRM_MODE_OBJECT_CRTC);
>  	if (!prop)
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index 2d1e9c9..ebde60e 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -144,6 +144,7 @@ struct __drm_crtcs_state {
>  	struct drm_crtc *ptr;
>  	struct drm_crtc_state *state;
>  	struct drm_crtc_commit *commit;
> +	u64 __user *out_fence_ptr;
>  };
>  
>  struct __drm_connnectors_state {
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 278dbdd..2539394 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -768,6 +768,18 @@ static inline struct drm_crtc *fence_to_crtc(struct dma_fence *fence)
>  }
>  
>  /**
> + * struct drm_out_fence_state - store out_fence data for install and clean up
> + * @out_fence_ptr: user pointer to store the fence fd in.
> + * @sync_file: sync_file related to the out_fence
> + * @fd: file descriptor to installed on the sync_file.
> + */
> +struct drm_out_fence_state {
> +	u64 __user *out_fence_ptr;
> +	struct sync_file *sync_file;
> +	int fd;
> +};

You only use this in drm_atomic.c, no need to have it in the header and
document it. Please move it into drm_atomic.c, right befoer it's used.

> +
> +/*
>   * struct drm_mode_set - new values for a CRTC config change
>   * @fb: framebuffer to use for new config
>   * @crtc: CRTC whose configuration we're about to change
> @@ -1245,6 +1257,11 @@ struct drm_mode_config {
>  	 */
>  	struct drm_property *prop_in_fence_fd;
>  	/**
> +	 * @prop_out_fence_ptr: Sync File fd pointer representing the
> +	 * outgoing fences for a CRTC.
> +	 */
> +	struct drm_property *prop_out_fence_ptr;
> +	/**
>  	 * @prop_crtc_id: Default atomic plane property to specify the
>  	 * &drm_crtc.
>  	 */
> -- 
> 2.5.5
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch