| Message ID | 20180918230637.20700-2-lyude@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fix legacy DPMS changes with MST | expand |
Hi Lyude,
Thank you for the patch! Perhaps something to improve:
url: https://github.com/0day-ci/linux/commits/Lyude-Paul/Fix-legacy-DPMS-changes-with-MST/20180919-203434
base: git://anongit.freedesktop.org/drm-intel for-linux-next
smatch warnings:
drivers/gpu/drm/drm_dp_mst_topology.c:3144 drm_dp_mst_connector_still_exists() error: we previously assumed 'port' could be null (see line 3146)
# https://github.com/0day-ci/linux/commit/f8df31d5221b9a6da6698d4a37e622253bb17cdc
git remote add linux-review https://github.com/0day-ci/linux
git remote update linux-review
git checkout f8df31d5221b9a6da6698d4a37e622253bb17cdc
vim +/port +3144 drivers/gpu/drm/drm_dp_mst_topology.c
3f3353b7 Pandiyan, Dhinakaran 2017-04-20 3131
f8df31d5 Lyude Paul 2018-09-18 3132 static bool
f8df31d5 Lyude Paul 2018-09-18 3133 drm_dp_mst_connector_still_exists(struct drm_connector *connector,
f8df31d5 Lyude Paul 2018-09-18 3134 struct drm_dp_mst_topology_mgr *mgr,
f8df31d5 Lyude Paul 2018-09-18 3135 struct drm_dp_mst_branch *mstb)
f8df31d5 Lyude Paul 2018-09-18 3136 {
f8df31d5 Lyude Paul 2018-09-18 3137 struct drm_dp_mst_port *port;
f8df31d5 Lyude Paul 2018-09-18 3138 bool exists = false;
f8df31d5 Lyude Paul 2018-09-18 3139
f8df31d5 Lyude Paul 2018-09-18 3140 mstb = drm_dp_get_validated_mstb_ref(mgr, mstb);
f8df31d5 Lyude Paul 2018-09-18 3141 if (!mstb)
f8df31d5 Lyude Paul 2018-09-18 3142 return false;
f8df31d5 Lyude Paul 2018-09-18 3143
f8df31d5 Lyude Paul 2018-09-18 @3144 list_for_each_entry(port, &mstb->ports, next) {
^^^^
We need to use a different loop iterator, or possibly
list_for_each_entry_safe() because it looks like we're freeing
something. Maybe it's cleanest to do both.
f8df31d5 Lyude Paul 2018-09-18 3145 port = drm_dp_get_validated_port_ref(mgr, port);
f8df31d5 Lyude Paul 2018-09-18 @3146 if (!port)
f8df31d5 Lyude Paul 2018-09-18 3147 continue;
f8df31d5 Lyude Paul 2018-09-18 3148
f8df31d5 Lyude Paul 2018-09-18 3149 exists = (port->connector == connector ||
f8df31d5 Lyude Paul 2018-09-18 3150 (port->mstb &&
f8df31d5 Lyude Paul 2018-09-18 3151 drm_dp_mst_connector_still_exists(connector, mgr,
f8df31d5 Lyude Paul 2018-09-18 3152 port->mstb)));
f8df31d5 Lyude Paul 2018-09-18 3153
f8df31d5 Lyude Paul 2018-09-18 3154 drm_dp_put_port(port);
f8df31d5 Lyude Paul 2018-09-18 3155 if (exists)
f8df31d5 Lyude Paul 2018-09-18 3156 break;
f8df31d5 Lyude Paul 2018-09-18 3157 }
f8df31d5 Lyude Paul 2018-09-18 3158
f8df31d5 Lyude Paul 2018-09-18 3159 drm_dp_put_mst_branch_device(mstb);
f8df31d5 Lyude Paul 2018-09-18 3160 return exists;
f8df31d5 Lyude Paul 2018-09-18 3161 }
f8df31d5 Lyude Paul 2018-09-18 3162
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
On 2018-09-18 07:06 PM, Lyude Paul wrote: > Currently the way that we prevent userspace from performing new modesets > on MST connectors that have just been destroyed is rather broken. > There's nothing in the actual DRM DP MST topology helpers that checks > whether or not a connector still exists, instead each DRM driver does > this on it's own, usually by returning NULL from the best_encoder > callback which in turn, causes the atomic commit to fail. > > However, this is wrong in a rather subtle way. If ->best_encoder() > returns NULL, this makes ALL modesets involving the connector fail. This > includes modesets from userspace that would shut off the CRTCs being > used by the connector. Since this results in blocking any changes to a > connector's DPMS prop, it has the sideaffect of preventing legacy > modesetting users from ever disabling a CRTC that was previously enabled > for use in an MST topology. An example of this, where X tries to > change the DPMS property of an MST connector that was just detached from > the system: > > [ 2908.320131] [drm:drm_helper_probe_single_connector_modes [drm_kms_helper]] [CONNECTOR:82:DP-6] > [ 2908.320148] [drm:drm_helper_probe_single_connector_modes [drm_kms_helper]] [CONNECTOR:82:DP-6] status updated from connected to disconnected > [ 2908.320166] [drm:drm_helper_probe_single_connector_modes [drm_kms_helper]] [CONNECTOR:82:DP-6] disconnected > [ 2908.320193] [drm:drm_mode_object_put.part.2 [drm]] OBJ ID: 111 (1) > [ 2908.320230] [drm:drm_sysfs_hotplug_event [drm]] generating hotplug event > ... > [ 2908.638539] [drm:drm_ioctl [drm]] pid=12928, dev=0xe201, auth=1, DRM_IOCTL_MODE_SETPROPERTY > [ 2908.638546] [drm:drm_atomic_state_init [drm]] Allocated atomic state 000000007155ba49 > [ 2908.638553] [drm:drm_mode_object_get [drm]] OBJ ID: 114 (1) > [ 2908.638560] [drm:drm_mode_object_get [drm]] OBJ ID: 108 (1) > [ 2908.638568] [drm:drm_atomic_get_crtc_state [drm]] Added [CRTC:41:head-0] 0000000097a6396e state to 000000007155ba49 > [ 2908.638575] [drm:drm_atomic_add_affected_connectors [drm]] Adding all current connectors for [CRTC:41:head-0] to 000000007155ba49 > [ 2908.638582] [drm:drm_mode_object_get [drm]] OBJ ID: 82 (3) > [ 2908.638589] [drm:drm_mode_object_get [drm]] OBJ ID: 82 (4) > [ 2908.638596] [drm:drm_atomic_get_connector_state [drm]] Added [CONNECTOR:82:DP-6] 0000000087427144 state to 000000007155ba49 > [ 2908.638603] [drm:drm_atomic_check_only [drm]] checking 000000007155ba49 > [ 2908.638609] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] [CRTC:41:head-0] active changed > [ 2908.638613] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] Updating routing for [CONNECTOR:82:DP-6] > [ 2908.638616] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] No suitable encoder found for [CONNECTOR:82:DP-6] > [ 2908.638623] [drm:drm_atomic_check_only [drm]] atomic driver check for 000000007155ba49 failed: -22 > [ 2908.638630] [drm:drm_atomic_state_default_clear [drm]] Clearing atomic state 000000007155ba49 > [ 2908.638637] [drm:drm_mode_object_put.part.2 [drm]] OBJ ID: 82 (4) > [ 2908.638643] [drm:drm_mode_object_put.part.2 [drm]] OBJ ID: 82 (3) > [ 2908.638650] [drm:drm_mode_object_put.part.2 [drm]] OBJ ID: 114 (2) > [ 2908.638656] [drm:drm_mode_object_put.part.2 [drm]] OBJ ID: 108 (2) > [ 2908.638663] [drm:__drm_atomic_state_free [drm]] Freeing atomic state 000000007155ba49 > [ 2908.638669] [drm:drm_mode_object_put.part.2 [drm]] OBJ ID: 82 (2) > [ 2908.638676] [drm:drm_ioctl [drm]] pid=12928, ret = -22 > > While this doesn't usually result in any errors that would be obvious to > the user, it does result in us leaving display resources on. This in > turn leads to unwanted sideaffects like inactive GPUs being left on > (usually from the resulting leaked runtime PM ref). > > So, provide an easier way of doing this that doesn't require breaking > ->best_encoder(): add a common drm_dp_mst_connector_atomic_check() > function that DRM drivers can call in order to have CRTC enabling > commits fail automatically if the MST port driving the connector no > longer exists. We'll also be able to expand upon this later as well once > we add MST fallback retraining support. > > Signed-off-by: Lyude Paul <lyude@redhat.com> > Cc: stable@vger.kernel.org This does seem like a saner way to handle the case when the MST connector is gone. As this doesn't currently seem to affect amdgpu directly and I therefore might miss something I'll leave the RB to someone else, but you have my Acked-by: Harry Wentland <harry.wentland@amd.com> Harry > --- > drivers/gpu/drm/drm_dp_mst_topology.c | 76 +++++++++++++++++++++++++++ > include/drm/drm_dp_mst_helper.h | 3 ++ > 2 files changed, 79 insertions(+) > > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c > index 7780567aa669..0162d4bf2549 100644 > --- a/drivers/gpu/drm/drm_dp_mst_topology.c > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c > @@ -3129,6 +3129,82 @@ static const struct drm_private_state_funcs mst_state_funcs = { > .atomic_destroy_state = drm_dp_mst_destroy_state, > }; > > +static bool > +drm_dp_mst_connector_still_exists(struct drm_connector *connector, > + struct drm_dp_mst_topology_mgr *mgr, > + struct drm_dp_mst_branch *mstb) > +{ > + struct drm_dp_mst_port *port; > + bool exists = false; > + > + mstb = drm_dp_get_validated_mstb_ref(mgr, mstb); > + if (!mstb) > + return false; > + > + list_for_each_entry(port, &mstb->ports, next) { > + port = drm_dp_get_validated_port_ref(mgr, port); > + if (!port) > + continue; > + > + exists = (port->connector == connector || > + (port->mstb && > + drm_dp_mst_connector_still_exists(connector, mgr, > + port->mstb))); > + > + drm_dp_put_port(port); > + if (exists) > + break; > + } > + > + drm_dp_put_mst_branch_device(mstb); > + return exists; > +} > + > +/** > + * drm_dp_mst_connector_atomic_check - Helper for validating a new atomic > + * state on an MST connector > + * @connector: drm connector > + * @connector_state: the new atomic state of @connector > + * @mgr: the MST topology mgr for @connector > + * > + * This function performs various atomic checks that apply to all drivers > + * using the DRM DP MST helpers. This should be called by all drivers at the > + * start of the atomic_check function for their MST connectors. > + * > + * Return 0 for success, or negative error code on failure. > + */ > +int > +drm_dp_mst_connector_atomic_check(struct drm_connector *connector, > + struct drm_connector_state *connector_state, > + struct drm_dp_mst_topology_mgr *mgr) > +{ > + struct drm_atomic_state *state = connector_state->state; > + struct drm_crtc *crtc = connector_state->crtc; > + struct drm_crtc_state *new_crtc_state; > + > + if (!crtc) > + return 0; > + > + new_crtc_state = drm_atomic_get_new_crtc_state(state, crtc); > + if (!new_crtc_state) > + return 0; > + > + if (!drm_atomic_crtc_needs_modeset(new_crtc_state) || > + !new_crtc_state->active) > + return 0; > + > + /* Make sure that the port for this MST connector still exists */ > + if (!drm_dp_mst_connector_still_exists(connector, mgr, > + mgr->mst_primary)) { > + DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] has disappeared from the MST topology\n", > + connector->base.id, connector->name); > + return -EINVAL; > + } > + > + return 0; > +} > +EXPORT_SYMBOL(drm_dp_mst_connector_atomic_check); > + > /** > * drm_atomic_get_mst_topology_state: get MST topology state > * > diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h > index 7f78d26a0766..8e33c2c85d1e 100644 > --- a/include/drm/drm_dp_mst_helper.h > +++ b/include/drm/drm_dp_mst_helper.h > @@ -625,6 +625,9 @@ void drm_dp_mst_topology_mgr_suspend(struct drm_dp_mst_topology_mgr *mgr); > int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr); > struct drm_dp_mst_topology_state *drm_atomic_get_mst_topology_state(struct drm_atomic_state *state, > struct drm_dp_mst_topology_mgr *mgr); > +int drm_dp_mst_connector_atomic_check(struct drm_connector *connector, > + struct drm_connector_state *connector_state, > + struct drm_dp_mst_topology_mgr *mgr); > int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state, > struct drm_dp_mst_topology_mgr *mgr, > struct drm_dp_mst_port *port, int pbn); >
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 7780567aa669..0162d4bf2549 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -3129,6 +3129,82 @@ static const struct drm_private_state_funcs mst_state_funcs = { .atomic_destroy_state = drm_dp_mst_destroy_state, }; +static bool +drm_dp_mst_connector_still_exists(struct drm_connector *connector, + struct drm_dp_mst_topology_mgr *mgr, + struct drm_dp_mst_branch *mstb) +{ + struct drm_dp_mst_port *port; + bool exists = false; + + mstb = drm_dp_get_validated_mstb_ref(mgr, mstb); + if (!mstb) + return false; + + list_for_each_entry(port, &mstb->ports, next) { + port = drm_dp_get_validated_port_ref(mgr, port); + if (!port) + continue; + + exists = (port->connector == connector || + (port->mstb && + drm_dp_mst_connector_still_exists(connector, mgr, + port->mstb))); + + drm_dp_put_port(port); + if (exists) + break; + } + + drm_dp_put_mst_branch_device(mstb); + return exists; +} + +/** + * drm_dp_mst_connector_atomic_check - Helper for validating a new atomic + * state on an MST connector + * @connector: drm connector + * @connector_state: the new atomic state of @connector + * @mgr: the MST topology mgr for @connector + * + * This function performs various atomic checks that apply to all drivers + * using the DRM DP MST helpers. This should be called by all drivers at the + * start of the atomic_check function for their MST connectors. + * + * Return 0 for success, or negative error code on failure. + */ +int +drm_dp_mst_connector_atomic_check(struct drm_connector *connector, + struct drm_connector_state *connector_state, + struct drm_dp_mst_topology_mgr *mgr) +{ + struct drm_atomic_state *state = connector_state->state; + struct drm_crtc *crtc = connector_state->crtc; + struct drm_crtc_state *new_crtc_state; + + if (!crtc) + return 0; + + new_crtc_state = drm_atomic_get_new_crtc_state(state, crtc); + if (!new_crtc_state) + return 0; + + if (!drm_atomic_crtc_needs_modeset(new_crtc_state) || + !new_crtc_state->active) + return 0; + + /* Make sure that the port for this MST connector still exists */ + if (!drm_dp_mst_connector_still_exists(connector, mgr, + mgr->mst_primary)) { + DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] has disappeared from the MST topology\n", + connector->base.id, connector->name); + return -EINVAL; + } + + return 0; +} +EXPORT_SYMBOL(drm_dp_mst_connector_atomic_check); + /** * drm_atomic_get_mst_topology_state: get MST topology state * diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h index 7f78d26a0766..8e33c2c85d1e 100644 --- a/include/drm/drm_dp_mst_helper.h +++ b/include/drm/drm_dp_mst_helper.h @@ -625,6 +625,9 @@ void drm_dp_mst_topology_mgr_suspend(struct drm_dp_mst_topology_mgr *mgr); int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr); struct drm_dp_mst_topology_state *drm_atomic_get_mst_topology_state(struct drm_atomic_state *state, struct drm_dp_mst_topology_mgr *mgr); +int drm_dp_mst_connector_atomic_check(struct drm_connector *connector, + struct drm_connector_state *connector_state, + struct drm_dp_mst_topology_mgr *mgr); int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port, int pbn);
Currently the way that we prevent userspace from performing new modesets on MST connectors that have just been destroyed is rather broken. There's nothing in the actual DRM DP MST topology helpers that checks whether or not a connector still exists, instead each DRM driver does this on it's own, usually by returning NULL from the best_encoder callback which in turn, causes the atomic commit to fail. However, this is wrong in a rather subtle way. If ->best_encoder() returns NULL, this makes ALL modesets involving the connector fail. This includes modesets from userspace that would shut off the CRTCs being used by the connector. Since this results in blocking any changes to a connector's DPMS prop, it has the sideaffect of preventing legacy modesetting users from ever disabling a CRTC that was previously enabled for use in an MST topology. An example of this, where X tries to change the DPMS property of an MST connector that was just detached from the system: [ 2908.320131] [drm:drm_helper_probe_single_connector_modes [drm_kms_helper]] [CONNECTOR:82:DP-6] [ 2908.320148] [drm:drm_helper_probe_single_connector_modes [drm_kms_helper]] [CONNECTOR:82:DP-6] status updated from connected to disconnected [ 2908.320166] [drm:drm_helper_probe_single_connector_modes [drm_kms_helper]] [CONNECTOR:82:DP-6] disconnected [ 2908.320193] [drm:drm_mode_object_put.part.2 [drm]] OBJ ID: 111 (1) [ 2908.320230] [drm:drm_sysfs_hotplug_event [drm]] generating hotplug event ... [ 2908.638539] [drm:drm_ioctl [drm]] pid=12928, dev=0xe201, auth=1, DRM_IOCTL_MODE_SETPROPERTY [ 2908.638546] [drm:drm_atomic_state_init [drm]] Allocated atomic state 000000007155ba49 [ 2908.638553] [drm:drm_mode_object_get [drm]] OBJ ID: 114 (1) [ 2908.638560] [drm:drm_mode_object_get [drm]] OBJ ID: 108 (1) [ 2908.638568] [drm:drm_atomic_get_crtc_state [drm]] Added [CRTC:41:head-0] 0000000097a6396e state to 000000007155ba49 [ 2908.638575] [drm:drm_atomic_add_affected_connectors [drm]] Adding all current connectors for [CRTC:41:head-0] to 000000007155ba49 [ 2908.638582] [drm:drm_mode_object_get [drm]] OBJ ID: 82 (3) [ 2908.638589] [drm:drm_mode_object_get [drm]] OBJ ID: 82 (4) [ 2908.638596] [drm:drm_atomic_get_connector_state [drm]] Added [CONNECTOR:82:DP-6] 0000000087427144 state to 000000007155ba49 [ 2908.638603] [drm:drm_atomic_check_only [drm]] checking 000000007155ba49 [ 2908.638609] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] [CRTC:41:head-0] active changed [ 2908.638613] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] Updating routing for [CONNECTOR:82:DP-6] [ 2908.638616] [drm:drm_atomic_helper_check_modeset [drm_kms_helper]] No suitable encoder found for [CONNECTOR:82:DP-6] [ 2908.638623] [drm:drm_atomic_check_only [drm]] atomic driver check for 000000007155ba49 failed: -22 [ 2908.638630] [drm:drm_atomic_state_default_clear [drm]] Clearing atomic state 000000007155ba49 [ 2908.638637] [drm:drm_mode_object_put.part.2 [drm]] OBJ ID: 82 (4) [ 2908.638643] [drm:drm_mode_object_put.part.2 [drm]] OBJ ID: 82 (3) [ 2908.638650] [drm:drm_mode_object_put.part.2 [drm]] OBJ ID: 114 (2) [ 2908.638656] [drm:drm_mode_object_put.part.2 [drm]] OBJ ID: 108 (2) [ 2908.638663] [drm:__drm_atomic_state_free [drm]] Freeing atomic state 000000007155ba49 [ 2908.638669] [drm:drm_mode_object_put.part.2 [drm]] OBJ ID: 82 (2) [ 2908.638676] [drm:drm_ioctl [drm]] pid=12928, ret = -22 While this doesn't usually result in any errors that would be obvious to the user, it does result in us leaving display resources on. This in turn leads to unwanted sideaffects like inactive GPUs being left on (usually from the resulting leaked runtime PM ref). So, provide an easier way of doing this that doesn't require breaking ->best_encoder(): add a common drm_dp_mst_connector_atomic_check() function that DRM drivers can call in order to have CRTC enabling commits fail automatically if the MST port driving the connector no longer exists. We'll also be able to expand upon this later as well once we add MST fallback retraining support. Signed-off-by: Lyude Paul <lyude@redhat.com> Cc: stable@vger.kernel.org --- drivers/gpu/drm/drm_dp_mst_topology.c | 76 +++++++++++++++++++++++++++ include/drm/drm_dp_mst_helper.h | 3 ++ 2 files changed, 79 insertions(+)