pm24.git/drivers/gpu/drm/drm_lease.c, branch v6.0

drm/lease: allow empty leases

2021-10-01T13:55:47Z

This can be used to create a separate DRM file description, thus creating a new GEM handle namespace. My use-case is wlroots. The library splits responsibilities between separate components: the GBM allocator creates buffers, the GLES2 renderer uses EGL to import them and render to them, the DRM backend imports the buffers and displays them. wlroots has a modular architecture, and any of these components can be swapped and replaced with something else. For instance, the pipeline can be set up so that the DRM dumb buffer allocator is used instead of GBM and the Pixman renderer is used instead of GLES2. Library users can also replace any of these components with their own custom one. DMA-BUFs are used to pass buffer references across components. We could use GEM handles instead, but this would result in pain if multiple GPUs are in use: wlroots copies buffers across GPUs as needed. Importing a GEM handle created on one GPU into a completely different GPU will blow up (fail at best, mix unrelated buffers otherwise). Everything is fine if all components use Mesa. However, this isn't always desirable. For instance when running with DRM dumb buffers and the Pixman software renderer it's unfortunate to depend on GBM in the DRM backend just to turn DMA-BUFs into FB IDs. GBM loads Mesa drivers to perform an action which has nothing driver-specific. Additionally, drivers will fail the import if the 3D engine can't use the imported buffer, for instance amdgpu will refuse to import DRM dumb buffers [1]. We might also want to be running with a Vulkan renderer and a Vulkan allocator in the future, and GBM wouldn't be welcome in this setup. To address this, GBM can be side-stepped in the DRM backend, and can be replaced with drmPrimeFDToHandle calls. However because of GEM handle reference counting issues, care must be taken to avoid double-closing the same GEM handle. In particular, it's not possible to share a DRM FD with GBM or EGL and perform some drmPrimeFDToHandle calls manually. So wlroots needs to re-open the DRM FD to create a new GEM handle namespace. However there's no guarantee that the file-system permissions will be set up so that the primary FD can be opened by the compsoitor. On modern systems seatd or logind is a privileged process responsible for doing this, and other processes aren't expected to do it. For historical reasons systemd still allows physically logged in users to open primary DRM nodes, but this doesn't work on non-systemd setups and it's desirable to lock them down at some point. Some might suggest to open the render node instead of re-opening the primary node. However some systems don't have a render node at all (e.g. no GPU, or a split render/display SoC). Solutions to this issue have been discussed in [2]. One solution would be to open the magic /proc/self/fd/ file, but it's a Linux-specific hack (wlroots supports BSDs too). Another solution is to add support for re-opening a DRM primary node to seatd/logind, but they don't support it now and really haven't been designed for this (logind would need to grow a completely new API, because it assumes unique dev_t IDs). Also this seems like pushing down a kernel limitation to user-space a bit too hard. Another solution is to allow creating empty DRM leases. The lessee FD would have its own GEM handle namespace, so wouldn't conflict wth GBM/EGL. It would have the master bit set, but would be able to manage zero resources. wlroots doesn't intend to share this FD with any other process. All in all IMHO that seems like a pretty reasonable solution to the issue at hand. Note, I've discussed with Jonas Ådahl and Mutter plans to adopt a similar design in the future. Example usage in wlroots is available at [3]. IGT test available at [4]. [1]: https://github.com/swaywm/wlroots/issues/2916 [2]: https://gitlab.freedesktop.org/mesa/drm/-/merge_requests/110 [3]: https://github.com/swaywm/wlroots/pull/3158 [4]: https://patchwork.freedesktop.org/series/94323/ Signed-off-by: Simon Ser Cc: Daniel Vetter Cc: Daniel Stone Cc: Pekka Paalanen Cc: Michel Dänzer Cc: Emil Velikov Cc: Keith Packard Cc: Boris Brezillon Cc: Dave Airlie Acked-by: Pekka Paalanen Reviewed-by: Daniel Stone Link: https://patchwork.freedesktop.org/patch/msgid/20210903130000.1590-2-contact@emersion.fr

drm: clean up unused kerneldoc in drm_lease.c

2021-07-30T09:55:41Z

The kerneldoc in drm_lease.c is unused because none of the functions are driver interfaces as the symbols are not exported. Since they aren't used and much of the existing comments don't provide any insights (e.g. they just repeat the function name or list out the function parameters), they should be removed to make them easier to maintain and to make useful info more obvious. As a note, many of the comments mention whether idr_mutex should be held, but these are mostly redundant in cases where the function contains lockdep assertions or grabs the mutex. To simplify review, here's the reasoning behind each update. drm_lease_owner: function name is self-descriptive _drm_find_lessee: function name is self-descriptive _drm_lease_held_master: function name and signature are self-descriptive _drm_has_leased: kerneldoc is summarized into a comment because the function name could be interpreted ambiguously (check if the object has been leased VS check if the master has a lease on the object) _drm_lease_held: Retain the idr_mutex comment because the function does not directly grab the mutex or use a lockdep assertion. Otherwise, the function name is self-descriptive. drm_lease_held: function name is self-descriptive drm_lease_filter_crtcs: Kerneldoc is summarized into a comment because the function name could be interpreted ambiguously (filter leases based on crtcs mask VS filter crtcs mask based on leases) drm_lease_create: Kerneldoc removed. Useful function details such as atomic leasing are retained. Errno interpretations are useful and retained. drm_lease_destroy: function name is self-descriptive. Additional information is also removed as they're already present as comments inside the function. _drm_lease_revoke: function name is self-descriptive drm_lease_revoke: function name is self-descriptive drm_mode_create_lease_ioctl: Kerneldoc removed, but useful function details retained. drm_mode_list_lessees_ioctl: function name is self-descriptive. Additional details restate what the code does. drm_mode_get_lease_ioctl: Function summary retained to clarify that it's the leased objects that are returned, not the lease structure. drm_mode_revoke_lease_ioctl: Kerneldoc removed, but useful function details retained. Signed-off-by: Desmond Cheong Zhi Xi Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210730051759.1570630-1-desmondcheongzx@gmail.com

drm: clarify usage of drm leases

2021-07-29T07:12:01Z

We make the following changes to the documentation of drm leases to make it easier to reason about their usage. In particular, we clarify the lifetime and locking rules of lease fields in drm_master: 1. Make it clear that &drm_device.mode_config.idr_mutex protects the lease idr and list structures for drm_master. The lessor field itself doesn't need to be protected as it doesn't change after it's set in drm_lease_create. 2. Add descriptions for the lifetime of lessors and leases. 3. Add an overview DOC: section in drm-uapi.rst that defines the terminology for drm leasing, and explains how leases work and why they're used. Signed-off-by: Desmond Cheong Zhi Xi Reviewed-by: Daniel Vetter Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210728102739.441543-1-desmondcheongzx@gmail.com

drm: protect drm_master pointers in drm_lease.c

2021-07-20T18:22:19Z

drm_file->master pointers should be protected by drm_device.master_mutex or drm_file.master_lookup_lock when being dereferenced. However, in drm_lease.c, there are multiple instances where drm_file->master is accessed and dereferenced while neither lock is held. This makes drm_lease.c vulnerable to use-after-free bugs. We address this issue in 2 ways: 1. Add a new drm_file_get_master() function that calls drm_master_get on drm_file->master while holding on to drm_file.master_lookup_lock. Since drm_master_get increments the reference count of master, this prevents master from being freed until we unreference it with drm_master_put. 2. In each case where drm_file->master is directly accessed and eventually dereferenced in drm_lease.c, we wrap the access in a call to the new drm_file_get_master function, then unreference the master pointer once we are done using it. Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi Reviewed-by: Emil Velikov Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210712043508.11584-6-desmondcheongzx@gmail.com

drm: Don't include drm_legacy.h in drm_lease.c

2021-05-17T19:19:22Z

DRM leases do not use DRM legacy code. Remove the rsp include statement. Signed-off-by: Thomas Zimmermann Acked-by: Jani Nikula Link: https://patchwork.freedesktop.org/patch/msgid/20210516185937.5644-4-tzimmermann@suse.de

drm : Insert blank lines after declarations.

2020-07-02T13:26:00Z

Resolve checkpatch issues for missing blank lines after declarations. Issues found in multiple files with checkpatch.pl. Signed-off-by: Suraj Upadhyay Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20200702131749.GA25710@blackclown

drm/lease: fix WARNING in idr_destroy

2020-03-18T13:42:18Z

drm_lease_create takes ownership of leases. And leases will be released by drm_master_put. drm_master_put ->drm_master_destroy ->idr_destroy So we needn't call idr_destroy again. Reported-and-tested-by: syzbot+05835159fe322770fe3d@syzkaller.appspotmail.com Signed-off-by: Qiujun Huang Cc: stable@vger.kernel.org Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/1584518030-4173-1-git-send-email-hqjagain@gmail.com

Merge v5.2-rc5 into drm-next

2019-06-19T10:07:29Z

Maarten needs -rc4 backmerged so he can pull in the fbcon notifier removal topic branch into drm-misc-next. Signed-off-by: Daniel Vetter

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157

2019-05-30T18:26:37Z

Based on 3 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version [author] [kishon] [vijay] [abraham] [i] [kishon]@[ti] [com] this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version [author] [graeme] [gregory] [gg]@[slimlogic] [co] [uk] [author] [kishon] [vijay] [abraham] [i] [kishon]@[ti] [com] [based] [on] [twl6030]_[usb] [c] [author] [hema] [hk] [hemahk]@[ti] [com] this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 1105 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Allison Randal Reviewed-by: Richard Fontana Reviewed-by: Kate Stewart Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070033.202006027@linutronix.de Signed-off-by: Greg Kroah-Hartman

drm: drop use of drmP.h in drm/*

2019-05-27T16:07:03Z

The use of the drmP.h header file is deprecated. Remove use from all files in drm/* so people do not look there and follow a bad example. Build tested allyesconfig,allmodconfig on x86, arm etc. Including alpha that is as always more challenging than the rest. Signed-off-by: Sam Ravnborg Acked-by: Daniel Vetter Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Sean Paul Cc: David Airlie Link: https://patchwork.freedesktop.org/patch/msgid/20190526173535.32701-8-sam@ravnborg.org