Message-ID: <20161028092344.GB29507@e106950-lin.cambridge.arm.com>
Date:   Fri, 28 Oct 2016 10:23:45 +0100
From:   Brian Starkey <brian.starkey@....com>
To:     Gustavo Padovan <gustavo@...ovan.org>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Daniel Stone <daniels@...labora.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Rob Clark <robdclark@...il.com>,
        Greg Hackmann <ghackmann@...gle.com>,
        John Harrison <John.C.Harrison@...el.com>,
        laurent.pinchart@...asonboard.com, seanpaul@...gle.com,
        marcheu@...gle.com, m.chehab@...sung.com,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Gustavo Padovan <gustavo.padovan@...labora.co.uk>
Subject: Re: [PATCH v6 6/6] drm/fence: add out-fences support

Hi Gustavo,

On Thu, Oct 27, 2016 at 05:37:11PM -0200, Gustavo Padovan wrote:
>From: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
>
>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@...labora.co.uk>
>---
> 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)

bikeshed: I'd rather these were called set/get_out_fence_ptr_for_crtc,
as they don't involve struct drm_fence at all.

>+{
>+	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.
>+ */
>+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)
>+{
>+	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);

I think you're missing some subscripting on fence_state in this loop.
Here you set fence_state->out_fence_ptr directly, whereas I guess it
should be fence_state[fence_idx].out_fence_ptr;

>+
>+		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);

Related to above, I think if you're going to manipulate the
fence_state array outside of setup_out_fence you should drop the
inline increment here, as it will be easy for a refactor to miss it
and add bugs.

>+			if (ret) {
>+				dma_fence_put(fence);
>+				goto out;
>+			}
>+
>+			crtc_state->event->base.fence = fence;
>+		}
> 	}
>
> 	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");
>+			}
> 		}
> 	}
>
>+	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;
>+};
>+
>+/*
>  * 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.
>+	 */

Is it worth noting that userspace should provide a pointer to a u64
and not a plain int? Either here or in some more detailed kernel-doc
for the OUT_FENCE_PTR property.

Cheers,
Brian

>+	struct drm_property *prop_out_fence_ptr;
>+	/**
> 	 * @prop_crtc_id: Default atomic plane property to specify the
> 	 * &drm_crtc.
> 	 */
>-- 
>2.5.5
>

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