Instead of distingting between shared and exclusive fences specify
the fence usage while adding fences.
Rework all drivers to use this interface instead and deprecate the old one.
v2: some kerneldoc comments suggested by Daniel
v3: fix a missing case in radeon
v4: rebase on nouveau changes, fix lockdep and temporary disable warning
v5: more documentation updates
v6: separate internal dma_resv changes from this patch, avoids to
disable warning temporary, rebase on upstream changes
v7: fix missed case in lima driver, minimize changes to i915_gem_busy_ioctl
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220407085946.744568-3-christian.koenig@amd.com
This change adds the dma_resv_usage enum and allows us to specify why a
dma_resv object is queried for its containing fences.
Additional to that a dma_resv_usage_rw() helper function is added to aid
retrieving the fences for a read or write userspace submission.
This is then deployed to the different query functions of the dma_resv
object and all of their users. When the write paratermer was previously
true we now use DMA_RESV_USAGE_WRITE and DMA_RESV_USAGE_READ otherwise.
v2: add KERNEL/OTHER in separate patch
v3: some kerneldoc suggestions by Daniel
v4: some more kerneldoc suggestions by Daniel, fix missing cases lost in
the rebase pointed out by Bas.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220407085946.744568-2-christian.koenig@amd.com
So far we had the approach of using a directed acyclic
graph with the dma_resv obj.
This turned out to have many downsides, especially it means
that every single driver and user of this interface needs
to be aware of this restriction when adding fences. If the
rules for the DAG are not followed then we end up with
potential hard to debug memory corruption, information
leaks or even elephant big security holes because we allow
userspace to access freed up memory.
Since we already took a step back from that by always
looking at all fences we now go a step further and stop
dropping the shared fences when a new exclusive one is
added.
v2: Drop some now superflous documentation
v3: Add some more documentation for the new handling.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220321135856.1331-11-christian.koenig@amd.com
Rename struct dma_buf_map to struct iosys_map and corresponding APIs.
Over time dma-buf-map grew up to more functionality than the one used by
dma-buf: in fact it's just a shim layer to abstract system memory, that
can be accessed via regular load and store, from IO memory that needs to
be acessed via arch helpers.
The idea is to extend this API so it can fulfill other needs, internal
to a single driver. Example: in the i915 driver it's desired to share
the implementation for integrated graphics, which uses mostly system
memory, with discrete graphics, which may need to access IO memory.
The conversion was mostly done with the following semantic patch:
@r1@
@@
- struct dma_buf_map
+ struct iosys_map
@r2@
@@
(
- DMA_BUF_MAP_INIT_VADDR
+ IOSYS_MAP_INIT_VADDR
|
- dma_buf_map_set_vaddr
+ iosys_map_set_vaddr
|
- dma_buf_map_set_vaddr_iomem
+ iosys_map_set_vaddr_iomem
|
- dma_buf_map_is_equal
+ iosys_map_is_equal
|
- dma_buf_map_is_null
+ iosys_map_is_null
|
- dma_buf_map_is_set
+ iosys_map_is_set
|
- dma_buf_map_clear
+ iosys_map_clear
|
- dma_buf_map_memcpy_to
+ iosys_map_memcpy_to
|
- dma_buf_map_incr
+ iosys_map_incr
)
@@
@@
- #include <linux/dma-buf-map.h>
+ #include <linux/iosys-map.h>
Then some files had their includes adjusted and some comments were
update to remove mentions to dma-buf-map.
Since this is not specific to dma-buf anymore, move the documentation to
the "Bus-Independent Device Accesses" section.
v2:
- Squash patches
v3:
- Fix wrong removal of dma-buf.h from MAINTAINERS
- Move documentation from dma-buf.rst to device-io.rst
v4:
- Change documentation title and level
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220204170541.829227-1-lucas.demarchi@intel.com
A typical collection of patches this cycle, mostly fixing with a few new
features:
- Fixes from static tools. clang warnings, dead code, unused variable,
coccinelle sweeps, etc
- Driver bug fixes and minor improvements in rxe, bnxt_re, hfi1, mlx5,
irdma, qedr
- rtrs ULP bug fixes an improvments
- Additional counters for bnxt_re
- Support verbs CQ notifications in EFA
- Continued reworking and fixing of rxe
- netlink control to enable/disable optional device counters
- rxe now can use AH objects for its UD path, fixing various bugs in the
process
- Add DMABUF support to EFA
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma
Pull rdma updates from Jason Gunthorpe:
"A typical collection of patches this cycle, mostly fixing with a few
new features:
- Fixes from static tools. clang warnings, dead code, unused
variable, coccinelle sweeps, etc
- Driver bug fixes and minor improvements in rxe, bnxt_re, hfi1,
mlx5, irdma, qedr
- rtrs ULP bug fixes an improvments
- Additional counters for bnxt_re
- Support verbs CQ notifications in EFA
- Continued reworking and fixing of rxe
- netlink control to enable/disable optional device counters
- rxe now can use AH objects for its UD path, fixing various bugs in
the process
- Add DMABUF support to EFA"
* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma: (103 commits)
RDMA/core: Require the driver to set the IOVA correctly during rereg_mr
RDMA/bnxt_re: Remove unsupported bnxt_re_modify_ah callback
RDMA/irdma: optimize rx path by removing unnecessary copy
RDMA/qed: Use helper function to set GUIDs
RDMA/hns: Use the core code to manage the fixed mmap entries
IB/opa_vnic: Rebranding of OPA VNIC driver to Cornelis Networks
IB/qib: Rebranding of qib driver to Cornelis Networks
IB/hfi1: Rebranding of hfi1 driver to Cornelis Networks
RDMA/bnxt_re: Use helper function to set GUIDs
RDMA/bnxt_re: Fix kernel panic when trying to access bnxt_re_stat_descs
RDMA/qedr: Fix NULL deref for query_qp on the GSI QP
RDMA/hns: Modify the value of MAX_LP_MSG_LEN to meet hardware compatibility
RDMA/hns: Fix initial arm_st of CQ
RDMA/rxe: Make rxe_type_info static const
RDMA/rxe: Use 'bitmap_zalloc()' when applicable
RDMA/rxe: Save a few bytes from struct rxe_pool
RDMA/irdma: Remove the unused variable local_qp
RDMA/core: Fix missed initialization of rdma_hw_stats::lock
RDMA/efa: Add support for dmabuf memory regions
RDMA/umem: Allow pinned dmabuf umem usage
...
The pin callback does not necessarily have to move the memory to system
memory, remove the sentence from the comment.
Link: https://lore.kernel.org/r/20211012120903.96933-2-galpress@amazon.com
Signed-off-by: Gal Pressman <galpress@amazon.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Daniel pointed me towards this function and there are multiple obvious problems
in the implementation.
First of all the retry loop is not working as intended. In general the retry
makes only sense if you grab the reference first and then check the sequence
values.
Then we should always also wait for the exclusive fence.
It's also good practice to keep the reference around when installing callbacks
to fences you don't own.
And last the whole implementation was unnecessary complex and rather hard to
understand which could lead to probably unexpected behavior of the IOCTL.
Fix all this by reworking the implementation from scratch. Dropping the
whole RCU approach and taking the lock instead.
Only mildly tested and needs a thoughtful review of the code.
Pushing through drm-misc-next to avoid merge conflicts and give the code
another round of testing.
v2: fix the reference counting as well
v3: keep the excl fence handling as is for stable
v4: back to testing all fences, drop RCU
v5: handle in and out separately
v6: add missing clear of events
v7: change coding style as suggested by Michel, drop unused variables
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Michel Dänzer <mdaenzer@redhat.com>
CC: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20210720131110.88512-1-christian.koenig@amd.com
Specifically document the new/clarified rules around how the shared
fences do not have any ordering requirements against the exclusive
fence.
But also document all the things a bit better, given how central
struct dma_resv to dynamic buffer management the docs have been very
inadequat.
- Lots more links to other pieces of the puzzle. Unfortunately
ttm_buffer_object has no docs, so no links :-(
- Explain/complain a bit about dma_resv_locking_ctx(). I still don't
like that one, but fixing the ttm call chains is going to be
horrible. Plus we want to plug in real slowpath locking when we do
that anyway.
- Main part of the patch is some actual docs for struct dma_resv.
Overall I think we still have a lot of bad naming in this area (e.g.
dma_resv.fence is singular, but contains the multiple shared fences),
but I think that's more indicative of how the semantics and rules are
just not great.
Another thing that's real awkard is how chaining exclusive fences
right now means direct dma_resv.exclusive_fence pointer access with an
rcu_assign_pointer. Not so great either.
v2:
- Fix a pile of typos (Matt, Jason)
- Hammer it in that breaking the rules leads to use-after-free issues
around dma-buf sharing (Christian)
Reviewed-by: Christian König <christian.koenig@amd.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Link: https://patchwork.freedesktop.org/patch/msgid/20210805104705.862416-21-daniel.vetter@ffwll.ch
The DMA-BUF attachment statistics form a subset of the DMA-BUF
sysfs statistics that recently merged to the drm-misc tree. They are not
UABI yet since they have not merged to the upstream Linux kernel.
Since there has been a reported a performance regression due to the
overhead of sysfs directory creation/teardown during
dma_buf_attach()/dma_buf_detach(), this patch deletes the DMA-BUF
attachment statistics from sysfs.
Fixes: bdb8d06dfe ("dmabuf: Add the capability to expose DMA-BUF stats in sysfs")
Signed-off-by: Hridya Valsaraju <hridya@google.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210713040742.2680135-1-hridya@google.com
Signed-off-by: Christian König <christian.koenig@amd.com>
Docs for struct dma_resv are fairly clear:
"A reservation object can have attached one exclusive fence (normally
associated with write operations) or N shared fences (read
operations)."
https://dri.freedesktop.org/docs/drm/driver-api/dma-buf.html#reservation-objects
Furthermore a review across all of upstream.
First of render drivers and how they set implicit fences:
- nouveau follows this contract, see in validate_fini_no_ticket()
nouveau_bo_fence(nvbo, fence, !!b->write_domains);
and that last boolean controls whether the exclusive or shared fence
slot is used.
- radeon follows this contract by setting
p->relocs[i].tv.num_shared = !r->write_domain;
in radeon_cs_parser_relocs(), which ensures that the call to
ttm_eu_fence_buffer_objects() in radeon_cs_parser_fini() will do the
right thing.
- vmwgfx seems to follow this contract with the shotgun approach of
always setting ttm_val_buf->num_shared = 0, which means
ttm_eu_fence_buffer_objects() will only use the exclusive slot.
- etnaviv follows this contract, as can be trivially seen by looking
at submit_attach_object_fences()
- i915 is a bit a convoluted maze with multiple paths leading to
i915_vma_move_to_active(). Which sets the exclusive flag if
EXEC_OBJECT_WRITE is set. This can either come as a buffer flag for
softpin mode, or through the write_domain when using relocations. It
follows this contract.
- lima follows this contract, see lima_gem_submit() which sets the
exclusive fence when the LIMA_SUBMIT_BO_WRITE flag is set for that
bo
- msm follows this contract, see msm_gpu_submit() which sets the
exclusive flag when the MSM_SUBMIT_BO_WRITE is set for that buffer
- panfrost follows this contract with the shotgun approach of just
always setting the exclusive fence, see
panfrost_attach_object_fences(). Benefits of a single engine I guess
- v3d follows this contract with the same shotgun approach in
v3d_attach_fences_and_unlock_reservation(), but it has at least an
XXX comment that maybe this should be improved
- v4c uses the same shotgun approach of always setting an exclusive
fence, see vc4_update_bo_seqnos()
- vgem also follows this contract, see vgem_fence_attach_ioctl() and
the VGEM_FENCE_WRITE. This is used in some igts to validate prime
sharing with i915.ko without the need of a 2nd gpu
- vritio follows this contract again with the shotgun approach of
always setting an exclusive fence, see virtio_gpu_array_add_fence()
This covers the setting of the exclusive fences when writing.
Synchronizing against the exclusive fence is a lot more tricky, and I
only spot checked a few:
- i915 does it, with the optional EXEC_OBJECT_ASYNC to skip all
implicit dependencies (which is used by vulkan)
- etnaviv does this. Implicit dependencies are collected in
submit_fence_sync(), again with an opt-out flag
ETNA_SUBMIT_NO_IMPLICIT. These are then picked up in
etnaviv_sched_dependency which is the
drm_sched_backend_ops->dependency callback.
- v4c seems to not do much here, maybe gets away with it by not having
a scheduler and only a single engine. Since all newer broadcom chips than
the OG vc4 use v3d for rendering, which follows this contract, the
impact of this issue is fairly small.
- v3d does this using the drm_gem_fence_array_add_implicit() helper,
which then it's drm_sched_backend_ops->dependency callback
v3d_job_dependency() picks up.
- panfrost is nice here and tracks the implicit fences in
panfrost_job->implicit_fences, which again the
drm_sched_backend_ops->dependency callback panfrost_job_dependency()
picks up. It is mildly questionable though since it only picks up
exclusive fences in panfrost_acquire_object_fences(), but not buggy
in practice because it also always sets the exclusive fence. It
should pick up both sets of fences, just in case there's ever going
to be a 2nd gpu in a SoC with a mali gpu. Or maybe a mali SoC with a
pcie port and a real gpu, which might actually happen eventually. A
bug, but easy to fix. Should probably use the
drm_gem_fence_array_add_implicit() helper.
- lima is nice an easy, uses drm_gem_fence_array_add_implicit() and
the same schema as v3d.
- msm is mildly entertaining. It also supports MSM_SUBMIT_NO_IMPLICIT,
but because it doesn't use the drm/scheduler it handles fences from
the wrong context with a synchronous dma_fence_wait. See
submit_fence_sync() leading to msm_gem_sync_object(). Investing into
a scheduler might be a good idea.
- all the remaining drivers are ttm based, where I hope they do
appropriately obey implicit fences already. I didn't do the full
audit there because a) not follow the contract would confuse ttm
quite well and b) reading non-standard scheduler and submit code
which isn't based on drm/scheduler is a pain.
Onwards to the display side.
- Any driver using the drm_gem_plane_helper_prepare_fb() helper will
correctly. Overwhelmingly most drivers get this right, except a few
totally dont. I'll follow up with a patch to make this the default
and avoid a bunch of bugs.
- I didn't audit the ttm drivers, but given that dma_resv started
there I hope they get this right.
In conclusion this IS the contract, both as documented and
overwhelmingly implemented, specically as implemented by all render
drivers except amdgpu.
Amdgpu tried to fix this already in
commit 049aca4363
Author: Christian König <christian.koenig@amd.com>
Date: Wed Sep 19 16:54:35 2018 +0200
drm/amdgpu: fix using shared fence for exported BOs v2
but this fix falls short on a number of areas:
- It's racy, by the time the buffer is shared it might be too late. To
make sure there's definitely never a problem we need to set the
fences correctly for any buffer that's potentially exportable.
- It's breaking uapi, dma-buf fds support poll() and differentitiate
between, which was introduced in
commit 9b495a5887
Author: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Date: Tue Jul 1 12:57:43 2014 +0200
dma-buf: add poll support, v3
- Christian König wants to nack new uapi building further on this
dma_resv contract because it breaks amdgpu, quoting
"Yeah, and that is exactly the reason why I will NAK this uAPI change.
"This doesn't works for amdgpu at all for the reasons outlined above."
https://lore.kernel.org/dri-devel/f2eb6751-2f82-9b23-f57e-548de5b729de@gmail.com/
Rejecting new development because your own driver is broken and
violates established cross driver contracts and uapi is really not
how upstream works.
Now this patch will have a severe performance impact on anything that
runs on multiple engines. So we can't just merge it outright, but need
a bit a plan:
- amdgpu needs a proper uapi for handling implicit fencing. The funny
thing is that to do it correctly, implicit fencing must be treated
as a very strange IPC mechanism for transporting fences, where both
setting the fence and dependency intercepts must be handled
explicitly. Current best practices is a per-bo flag to indicate
writes, and a per-bo flag to to skip implicit fencing in the CS
ioctl as a new chunk.
- Since amdgpu has been shipping with broken behaviour we need an
opt-out flag from the butchered implicit fencing model to enable the
proper explicit implicit fencing model.
- for kernel memory fences due to bo moves at least the i915 idea is
to use ttm_bo->moving. amdgpu probably needs the same.
- since the current p2p dma-buf interface assumes the kernel memory
fence is in the exclusive dma_resv fence slot we need to add a new
fence slot for kernel fences, which must never be ignored. Since
currently only amdgpu supports this there's no real problem here
yet, until amdgpu gains a NO_IMPLICIT CS flag.
- New userspace needs to ship in enough desktop distros so that users
wont notice the perf impact. I think we can ignore LTS distros who
upgrade their kernels but not their mesa3d snapshot.
- Then when this is all in place we can merge this patch here.
What is not a solution to this problem here is trying to make the
dma_resv rules in the kernel more clever. The fundamental issue here
is that the amdgpu CS uapi is the least expressive one across all
drivers (only equalled by panfrost, which has an actual excuse) by not
allowing any userspace control over how implicit sync is conducted.
Until this is fixed it's completely pointless to make the kernel more
clever to improve amdgpu, because all we're doing is papering over
this uapi design issue. amdgpu needs to attain the status quo
established by other drivers first, once that's achieved we can tackle
the remaining issues in a consistent way across drivers.
v2: Bas pointed me at AMDGPU_GEM_CREATE_EXPLICIT_SYNC, which I
entirely missed.
This is great because it means the amdgpu specific piece for proper
implicit fence handling exists already, and that since a while. The
only thing that's now missing is
- fishing the implicit fences out of a shared object at the right time
- setting the exclusive implicit fence slot at the right time.
Jason has a patch series to fill that gap with a bunch of generic
ioctl on the dma-buf fd:
https://lore.kernel.org/dri-devel/20210520190007.534046-1-jason@jlekstrand.net/
v3: Since Christian has fixed amdgpu now in
commit 8c505bdc9c (drm-misc/drm-misc-next)
Author: Christian König <christian.koenig@amd.com>
Date: Wed Jun 9 13:51:36 2021 +0200
drm/amdgpu: rework dma_resv handling v3
Use the audit covered in this commit message as the excuse to update
the dma-buf docs around dma_buf.resv usage across drivers.
Since dynamic importers have different rules also hammer these in
again while we're at it.
v4:
- Add the missing "through the device" in the dynamic section that I
overlooked.
- Fix a kerneldoc markup mistake, the link didn't connect
v5:
- A few s/should/must/ to make clear what must be done (if the driver
does implicit sync) and what's more a maybe (Daniel Stone)
- drop all the example api discussion, that needs to be expanded,
clarified and put into a new chapter in drm-uapi.rst (Daniel Stone)
Cc: Daniel Stone <daniel@fooishbar.org>
Acked-by: Daniel Stone <daniel@fooishbar.org>
Reviewed-by: Dave Airlie <airlied@redhat.com> (v4)
Reviewed-by: Christian König <christian.koenig@amd.com> (v3)
Cc: mesa-dev@lists.freedesktop.org
Cc: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Rob Clark <robdclark@chromium.org>
Cc: Kristian H. Kristensen <hoegsberg@google.com>
Cc: Michel Dänzer <michel@daenzer.net>
Cc: Daniel Stone <daniels@collabora.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Deepak R Varma <mh12gx2825@gmail.com>
Cc: Chen Li <chenli@uniontech.com>
Cc: Kevin Wang <kevin1.wang@amd.com>
Cc: Dennis Li <Dennis.Li@amd.com>
Cc: Luben Tuikov <luben.tuikov@amd.com>
Cc: linaro-mm-sig@lists.linaro.org
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210624125246.166721-1-daniel.vetter@ffwll.ch
Also review & update everything while we're at it.
This is prep work to smash a ton of stuff into the kerneldoc for
@resv.
v2: Move the doc for sysfs_entry.attachment_uid to the right place too
(Sam)
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Christian König <christian.koenig@amd.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Nirmoy Das <nirmoy.das@amd.com>
Cc: Deepak R Varma <mh12gx2825@gmail.com>
Cc: Chen Li <chenli@uniontech.com>
Cc: Kevin Wang <kevin1.wang@amd.com>
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Link: https://patchwork.freedesktop.org/patch/msgid/20210623161712.3370885-1-daniel.vetter@ffwll.ch
Christian and me realized we have a pretty massive disconnect about
different interpretations of what dma_resv is used for by different
drivers. The discussion is much, much bigger than this change here,
but this is an important one:
Non-dynamic exporters must guarantee that the memory they return is
ready for use. They cannot expect importers to wait for the exclusive
fence. Only dynamic importers are required to obey the dma_resv fences
strictly (and more patches are needed to define exactly what this
means).
Christian has patches to update nouvea, radeon and amdgpu. The only
other driver using both ttm and supporting dma-buf export is qxl,
which only uses synchronous ttm_bo_move.
v2: To hammer this in document that dynamic importers _must_ wait for
the exclusive fence after having called dma_buf_map_attachment.
Reviewed-by: Christian König <christian.koenig@amd.com>
Cc: Christian König <ckoenig.leichtzumerken@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210621151758.2347474-1-daniel.vetter@ffwll.ch
Overview
========
The patch adds DMA-BUF statistics to /sys/kernel/dmabuf/buffers. It
allows statistics to be enabled for each DMA-BUF in sysfs by enabling
the config CONFIG_DMABUF_SYSFS_STATS.
The following stats will be exposed by the interface:
/sys/kernel/dmabuf/buffers/<inode_number>/exporter_name
/sys/kernel/dmabuf/buffers/<inode_number>/size
/sys/kernel/dmabuf/buffers/<inode_number>/attachments/<attach_uid>/device
/sys/kernel/dmabuf/buffers/<inode_number>/attachments/<attach_uid>/map_counter
The inode_number is unique for each DMA-BUF and was added earlier [1]
in order to allow userspace to track DMA-BUF usage across different
processes.
Use Cases
=========
The interface provides a way to gather DMA-BUF per-buffer statistics
from production devices. These statistics will be used to derive DMA-BUF
per-exporter stats and per-device usage stats for Android Bug reports.
The corresponding userspace changes can be found at [2].
Telemetry tools will also capture this information(along with other
memory metrics) periodically as well as on important events like a
foreground app kill (which might have been triggered by Low Memory
Killer). It will also contribute to provide a snapshot of the system
memory usage on other events such as OOM kills and Application Not
Responding events.
Background
==========
Currently, there are two existing interfaces that provide information
about DMA-BUFs.
1) /sys/kernel/debug/dma_buf/bufinfo
debugfs is however unsuitable to be mounted in production systems and
cannot be considered as an alternative to the sysfs interface being
proposed.
2) proc/<pid>/fdinfo/<fd>
The proc/<pid>/fdinfo/<fd> files expose information about DMA-BUF fds.
However, the existing procfs interfaces can only provide information
about the buffers for which processes hold fds or have the buffers
mmapped into their address space. Since the procfs interfaces alone
cannot provide a full picture of all DMA-BUFs in the system, there is
the need for an alternate interface to provide this information on
production systems.
The patch contains the following major improvements over v1:
1) Each attachment is represented by its own directory to allow creating
a symlink to the importing device and to also provide room for future
expansion.
2) The number of distinct mappings of each attachment is exposed in a
separate file.
3) The per-buffer statistics are now in /sys/kernel/dmabuf/buffers
inorder to make the interface expandable in future.
All of the improvements above are based on suggestions/feedback from
Daniel Vetter and Christian König.
A shell script that can be run on a classic Linux environment to read
out the DMA-BUF statistics can be found at [3](suggested by John
Stultz).
[1]: https://lore.kernel.org/patchwork/patch/1088791/
[2]: https://android-review.googlesource.com/q/topic:%22dmabuf-sysfs%22+(status:open%20OR%20status:merged)
[3]: https://android-review.googlesource.com/c/platform/system/memory/libmeminfo/+/1549734
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Hridya Valsaraju <hridya@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210603214758.2955251-1-hridya@google.com
We have too many people abusing the struct page they can get at but
really shouldn't in importers. Aside from that the backing page might
simply not exist (for dynamic p2p mappings) looking at it and using it
e.g. for mmap can also wreak the page handling of the exporter
completely. Importers really must go through the proper interface like
dma_buf_mmap for everything.
I'm semi-tempted to enforce this for dynamic importers since those
really have no excuse at all to break the rules.
Unfortuantely we can't store the right pointers somewhere safe to make
sure we oops on something recognizable, so best is to just wrangle
them a bit by flipping all the bits. At least on x86 kernel addresses
have all their high bits sets and the struct page array is fairly low
in the kernel mapping, so flipping all the bits gives us a very high
pointer in userspace and hence excellent chances for an invalid
dereference.
v2: Add a note to the @map_dma_buf hook that exporters shouldn't do
fancy caching tricks, which would blow up with this address scrambling
trick here (Chris)
Enable by default when CONFIG_DMA_API_DEBUG is enabled.
v3: Only one copy of the mangle/unmangle code (Christian)
v4: #ifdef, not #if (0day)
v5: sg_table can also be an ERR_PTR (Chris, Christian)
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Stevens <stevensd@chromium.org>
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Link: https://patchwork.freedesktop.org/patch/msgid/20210115164739.3958206-1-daniel.vetter@ffwll.ch
Motivated by a discussion with Christian and Thomas: Try to untangle a
bit what's relevant for importers and what's relevant for exporters.
Also add an assert that really only dynamic importers use the api
function, anything else doesn't make sense.
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Link: https://patchwork.freedesktop.org/patch/msgid/20201211155843.3348718-4-daniel.vetter@ffwll.ch
The fact that the size of dma-buf is invariant over the lifetime of the
buffer is mentioned in the comment of 'dma_buf_ops.mmap', but is not
documented at where the info is defined. Add the missing documentation.
Signed-off-by: Jianxin Xiong <jianxin.xiong@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1605044477-51833-7-git-send-email-jianxin.xiong@intel.com
The dma-buf API have been used under the assumption that the sg lists
returned from dma_buf_map_attachment() are fully page aligned. Lots of
stuff can break otherwise all over the place. Clarify this in the
documentation and add a check when DMA API debug is enabled.
Signed-off-by: Jianxin Xiong <jianxin.xiong@intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1602692161-107096-1-git-send-email-jianxin.xiong@intel.com
This patch updates dma_buf_vunmap() and dma-buf's vunmap callback to
use struct dma_buf_map. The interfaces used to receive a buffer address.
This address is now given in an instance of the structure.
Users of the functions are updated accordingly. This is only an interface
change. It is currently expected that dma-buf memory can be accessed with
system memory load/store operations.
v2:
* include dma-buf-heaps and i915 selftests (kernel test robot)
* initialize cma_obj before using it in drm_gem_cma_free_object()
(kernel test robot)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Tomasz Figa <tfiga@chromium.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200925115601.23955-4-tzimmermann@suse.de
This patch updates dma_buf_vmap() and dma-buf's vmap callback to use
struct dma_buf_map.
The interfaces used to return a buffer address. This address now gets
stored in an instance of the structure that is given as an additional
argument. The functions return an errno code on errors.
Users of the functions are updated accordingly. This is only an interface
change. It is currently expected that dma-buf memory can be accessed with
system memory load/store operations.
v3:
* update fastrpc driver (kernel test robot)
v2:
* always clear map parameter in dma_buf_vmap() (Daniel)
* include dma-buf-heaps and i915 selftests (kernel test robot)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Tomasz Figa <tfiga@chromium.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200925115601.23955-3-tzimmermann@suse.de
The new type struct dma_buf_map represents a mapping of dma-buf memory
into kernel space. It contains a flag, is_iomem, that signals users to
access the mapped memory with I/O operations instead of regular loads
and stores.
It was assumed that DMA buffer memory can be accessed with regular load
and store operations. Some architectures, such as sparc64, require the
use of I/O operations to access dma-map buffers that are located in I/O
memory. Providing struct dma_buf_map allows drivers to implement this.
This was specifically a problem when refreshing the graphics framebuffer
on such systems. [1]
As the first step, struct dma_buf stores an instance of struct dma_buf_map
internally. Afterwards, dma-buf's vmap and vunmap interfaces are be
converted. Finally, affected drivers can be fixed.
v3:
* moved documentation into separate patch
* test for NULL pointers with !<ptr>
[1] https://lore.kernel.org/dri-devel/20200725191012.GA434957@ravnborg.org/
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200925115601.23955-2-tzimmermann@suse.de
Fix kernel-doc warning in <linux/dma-buf.h>:
../include/linux/dma-buf.h:330: warning: Function parameter or member 'name_lock' not described in 'dma_buf'
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Gustavo Padovan <gustavo@padovan.org>
Cc: Christian König <christian.koenig@amd.com>
Cc: linux-media@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/388523/
Signed-off-by: Christian König <christian.koenig@amd.com>
There exists a sleep-while-atomic bug while accessing the dmabuf->name
under mutex in the dmabuffs_dname(). This is caused from the SELinux
permissions checks on a process where it tries to validate the inherited
files from fork() by traversing them through iterate_fd() (which
traverse files under spin_lock) and call
match_file(security/selinux/hooks.c) where the permission checks happen.
This audit information is logged using dump_common_audit_data() where it
calls d_path() to get the file path name. If the file check happen on
the dmabuf's fd, then it ends up in ->dmabuffs_dname() and use mutex to
access dmabuf->name. The flow will be like below:
flush_unauthorized_files()
iterate_fd()
spin_lock() --> Start of the atomic section.
match_file()
file_has_perm()
avc_has_perm()
avc_audit()
slow_avc_audit()
common_lsm_audit()
dump_common_audit_data()
audit_log_d_path()
d_path()
dmabuffs_dname()
mutex_lock()--> Sleep while atomic.
Call trace captured (on 4.19 kernels) is below:
___might_sleep+0x204/0x208
__might_sleep+0x50/0x88
__mutex_lock_common+0x5c/0x1068
__mutex_lock_common+0x5c/0x1068
mutex_lock_nested+0x40/0x50
dmabuffs_dname+0xa0/0x170
d_path+0x84/0x290
audit_log_d_path+0x74/0x130
common_lsm_audit+0x334/0x6e8
slow_avc_audit+0xb8/0xf8
avc_has_perm+0x154/0x218
file_has_perm+0x70/0x180
match_file+0x60/0x78
iterate_fd+0x128/0x168
selinux_bprm_committing_creds+0x178/0x248
security_bprm_committing_creds+0x30/0x48
install_exec_creds+0x1c/0x68
load_elf_binary+0x3a4/0x14e0
search_binary_handler+0xb0/0x1e0
So, use spinlock to access dmabuf->name to avoid sleep-while-atomic.
Cc: <stable@vger.kernel.org> [5.3+]
Signed-off-by: Charan Teja Kalla <charante@codeaurora.org>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Acked-by: Christian König <christian.koenig@amd.com>
[sumits: added comment to spinlock_t definition to avoid warning]
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/a83e7f0d-4e54-9848-4b58-e1acdbe06735@codeaurora.org
Fix documentation warnings in dma-buf.[hc]:
../drivers/dma-buf/dma-buf.c:678: warning: Function parameter or member 'importer_ops' not described in 'dma_buf_dynamic_attach'
../drivers/dma-buf/dma-buf.c:678: warning: Function parameter or member 'importer_priv' not described in 'dma_buf_dynamic_attach'
../include/linux/dma-buf.h:339: warning: Incorrect use of kernel-doc format: * @move_notify
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: linux-media@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linaro-mm-sig@lists.linaro.org
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/7bcbe6fe-0b4b-87da-d003-b68a26eb4cf0@infradead.org
Add a peer2peer flag noting that the importer can deal with device
resources which are not backed by pages.
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/359286/
Instead use the pin() callback to detect dynamic DMA-buf handling.
Since amdgpu is now migrated it doesn't make much sense to keep
the extra flag.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/353997/?series=73646&rev=1
On the exporter side we add optional explicit pinning callbacks. Which are
called when the importer doesn't implement dynamic handling, move notification
or need the DMA-buf locked in place for its use case.
On the importer side we add an optional move_notify callback. This callback is
used by the exporter to inform the importers that their mappings should be
destroyed as soon as possible.
This allows the exporter to provide the mappings without the need to pin
the backing store.
v2: don't try to invalidate mappings when the callback is NULL,
lock the reservation obj while using the attachments,
add helper to set the callback
v3: move flag for invalidation support into the DMA-buf,
use new attach_info structure to set the callback
v4: use importer_priv field instead of mangling exporter priv.
v5: drop invalidation_supported flag
v6: squash together with pin/unpin changes
v7: pin/unpin takes an attachment now
v8: nuke dma_buf_attachment_(map|unmap)_locked,
everything is now handled backward compatible
v9: always cache when export/importer don't agree on dynamic handling
v10: minimal style cleanup
v11: drop automatically re-entry avoidance
v12: rename callback to move_notify
v13: add might_lock in appropriate places
v14: rebase on separated locking change
v15: add EXPERIMENTAL flag, some more code comments
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/353993/?series=73646&rev=1
It's unused.
10 years ago, back when 32bit was still fairly common and trying to
not exhaust vmalloc space sounded like a worthwhile goal, adding these
to dma_buf made sense.
Reality is that they simply never caught on, and nowadays everyone who
needs plenty of buffers will run in 64bit mode anyway.
Also update the docs in this area to adjust them to reality.
The actual hooks in dma_buf_ops will be removed once all the
implementations are gone.
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Link: https://patchwork.freedesktop.org/patch/msgid/20191118103536.17675-10-daniel.vetter@ffwll.ch
This patch is a stripped down version of the locking changes
necessary to support dynamic DMA-buf handling.
It adds a dynamic flag for both importers as well as exporters
so that drivers can choose if they want the reservation object
locked or unlocked during mapping of attachments.
For compatibility between drivers we cache the DMA-buf mapping
during attaching an importer as soon as exporter/importer
disagree on the dynamic handling.
Issues and solutions we considered:
- We can't change all existing drivers, and existing improters have
strong opinions about which locks they're holding while calling
dma_buf_attachment_map/unmap. Exporters also have strong opinions about
which locks they can acquire in their ->map/unmap callbacks, levaing no
room for change. The solution to avoid this was to move the
actual map/unmap out from this call, into the attach/detach callbacks,
and cache the mapping. This works because drivers don't call
attach/detach from deep within their code callchains (like deep in
memory management code called from cs/execbuf ioctl), but directly from
the fd2handle implementation.
- The caching has some troubles on some soc drivers, which set other modes
than DMA_BIDIRECTIONAL. We can't have 2 incompatible mappings, and we
can't re-create the mapping at _map time due to the above locking fun.
We very carefuly step around that by only caching at attach time if the
dynamic mode between importer/expoert mismatches.
- There's been quite some discussion on dma-buf mappings which need active
cache management, which would all break down when caching, plus we don't
have explicit flush operations on the attachment side. The solution to
this was to shrug and keep the current discrepancy between what the
dma-buf docs claim and what implementations do, with the hope that the
begin/end_cpu_access hooks are good enough and that all necessary
flushing to keep device mappings consistent will be done there.
v2: cleanup set_name merge, improve kerneldoc
v3: update commit message, kerneldoc and cleanup _debug_show()
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/336788/
Be more consistent with the naming of the other DMA-buf objects.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/323401/
Based on 1 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 version 2 as
published by the free software foundation 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 you should have received a copy of the gnu general
public license along with this program if not see http www gnu org
licenses
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 503 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Enrico Weigelt <info@metux.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190602204653.811534538@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This patch adds complimentary DMA_BUF_SET_NAME ioctls, which lets
userspace processes attach a free-form name to each buffer.
This information can be extremely helpful for tracking and accounting
shared buffers. For example, on Android, we know what each buffer will
be used for at allocation time: GL, multimedia, camera, etc. The
userspace allocator can use DMA_BUF_SET_NAME to associate that
information with the buffer, so we can later give developers a
breakdown of how much memory they're allocating for graphics, camera,
etc.
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Chenbo Feng <fengc@google.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190613223408.139221-3-fengc@google.com
To allow a smooth transition from pinning buffer objects to dynamic
invalidation we first start to cache the sg_table for an attachment.
v2: keep closer to the DRM implementation
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.kernel.org/patch/10943053/
Other function have inline documentation, a couple still have
theirs at the top of the structure, update the docs and move
them inline.
Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190321200957.16938-2-afd@ti.com
Neither used nor correctly implemented anywhere. Just completely remove
the interface.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/226645/
The device parameter is completely unused because it is available in the
attachment structure as well.
v2: fix kerneldoc as well
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/226643/
Seeing the kunmap_atomic dma_buf_ops share the same name with a macro
in highmem.h, the former can be aliased if any dma-buf user includes
that header.
I'm personally trying to include highmem.h inside scatterlist.h and this
breaks the dma-buf code proper.
Christoph Hellwig suggested [1] renaming it and pushing this patch ASAP.
To maintain consistency I've renamed all four of kmap* and kunmap* to be
map* and unmap*. (Even though only kmap_atomic presently conflicts.)
[1] https://www.spinics.net/lists/target-devel/msg15070.html
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1492630570-879-1-git-send-email-logang@deltatee.com
I just learned that &struct_name.member_name works and looks pretty
even. It doesn't (yet) link to the member directly though, which would
be really good for big structures or vfunc tables (where the
per-member kerneldoc tends to be long).
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1483044517-5770-5-git-send-email-daniel.vetter@ffwll.ch
sed -e 's/\( \* .*\)struct &\([_a-z]*\)/\1\&struct \2/' -i
Originally I wasnt a friend of this style because I thought a
line-break between the "&struct" and "foo" part would break it. But a
quick test shows that " * &struct \n * foo\n" works pefectly well with
current kernel-doc. So time to mass-apply these changes!
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1483044517-5770-4-git-send-email-daniel.vetter@ffwll.ch
Christian König
Maxime Ripard
Lucas De Marchi
Thomas Zimmermann
Linus Torvalds
Gal Pressman
Daniel Vetter
Hridya Valsaraju
Jianxin Xiong
Randy Dunlap
Charan Teja Kalla
Thomas Gleixner
Greg Hackmann
Andrew F. Davis
Gerd Hoffmann
Al Viro
Logan Gunthorpe