[PATCH v3 0/5] DRM scheduler kunit tests

Thu Mar 6 15:18:59 UTC 2025

On 06/03/2025 14:56, Tvrtko Ursulin wrote:
> 
> On 06/03/2025 12:37, Philipp Stanner wrote:
>> On Tue, 2025-03-04 at 13:10 +0000, Tvrtko Ursulin wrote:
>>> There has repeatedly been quite a bit of apprehension when any change
>>> to the DRM
>>> scheduler is proposed, with two main reasons being code base is
>>> considered
>>> fragile, not well understood and not very well documented, and
>>> secondly the lack
>>> of systematic testing outside the vendor specific tests suites and/or
>>> test
>>> farms.
>>>
>>> This series is an attempt to dislodge this status quo by adding some
>>> unit tests
>>> using the kunit framework.
>>>
>>> General approach is that there is a mock "hardware" backend which can
>>> be
>>> controlled from tests, which in turn allows exercising various
>>> scheduler code
>>> paths.
>>>
>>> Only some simple basic tests get added in the series and hopefully it
>>> is easy to
>>> understand what tests are doing.
>>>
>>> An obligatory "screenshot" for reference:
>>>
>>> [14:29:37] ============ drm_sched_basic_tests (3 subtests)
>>> ============
>>> [14:29:38] [PASSED] drm_sched_basic_submit
>>> [14:29:38] ================== drm_sched_basic_test
>>> ===================
>>> [14:29:38] [PASSED] A queue of jobs in a single entity
>>> [14:29:38] [PASSED] A chain of dependent jobs across multiple
>>> entities
>>> [14:29:38] [PASSED] Multiple independent job queues
>>> [14:29:38] [PASSED] Multiple inter-dependent job queues
>>> [14:29:38] ============== [PASSED] drm_sched_basic_test
>>> ===============
>>> [14:29:38] [PASSED] drm_sched_basic_entity_cleanup
>>> [14:29:38] ============== [PASSED] drm_sched_basic_tests
>>> ==============
>>> [14:29:38] ======== drm_sched_basic_timeout_tests (1 subtest)
>>> =========
>>> [14:29:40] [PASSED] drm_sched_basic_timeout
>>> [14:29:40] ========== [PASSED] drm_sched_basic_timeout_tests
>>> ==========
>>> [14:29:40] ======= drm_sched_basic_priority_tests (2 subtests)
>>> ========
>>> [14:29:42] [PASSED] drm_sched_priorities
>>> [14:29:42] [PASSED] drm_sched_change_priority
>>> [14:29:42] ========= [PASSED] drm_sched_basic_priority_tests
>>> ==========
>>> [14:29:42] ====== drm_sched_basic_modify_sched_tests (1 subtest)
>>> ======
>>> [14:29:43] [PASSED] drm_sched_test_modify_sched
>>> [14:29:43] ======= [PASSED] drm_sched_basic_modify_sched_tests
>>> ========
>>> [14:29:43]
>>> ============================================================
>>> [14:29:43] Testing complete. Ran 10 tests: passed: 10
>>> [14:29:43] Elapsed time: 13.330s total, 0.001s configuring, 4.005s
>>> building, 9.276s running
>>
>> Yo,
>>
>> so I tried to test this all this in QEMU and I am encountering some
>> explosions when I activate the scheduler tests. Just DRM tests boot
>> fine.
>>
>> I'm using a kernel on relatively current drm-misc-next: 44d2f310f008
>>
>> I apply your series, then
>> make defconfig
>> make menuconfig # switch on kunit framework and scheduler tests
>> install everything + initramfs
>>
>> Boot then causes errors as below. Just using the DRM kunit tests works
>> fine.
>>
>> Excerpt of the first fault:
>>
>> [    1.040513] # kunit_device: pass:3 fail:0 skip:0 total:3
>> [    1.040867] # Totals: pass:3 fail:0 skip:0 total:3
>> [    1.041296] ok 7 kunit_device
>> [    1.041936]     KTAP version 1
>> [    1.042186]     # Subtest: kunit_fault
>> [    1.042517]     # module: kunit_test
>> [    1.042517]     1..1
>> [    1.043147] BUG: kernel NULL pointer dereference, address: 
>> 0000000000000000
>> [    1.043765] #PF: supervisor write access in kernel mode
>> [    1.044189] #PF: error_code(0x0002) - not-present page
>> [    1.044617] PGD 0 P4D 0
>> [    1.044818] Oops: Oops: 0002 [#1] PREEMPT SMP PTI
>> [    1.045380] CPU: 7 UID: 0 PID: 214 Comm: kunit_try_catch Tainted: 
>> G                 N 6.14.0-rc4-00387-g33e4632926a0 #8
>> [    1.046262] Tainted: [N]=TEST
>> [    1.046521] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), 
>> BIOS 1.16.3-2.fc40 04/01/2014
>> [    1.047224] RIP: 0010:kunit_test_null_dereference+0x37/0x80
>> [    1.047706] Code: 80 b5 49 c7 c0 50 7f 56 b4 ba 01 00 00 00 65 48 
>> 8b 04 25 28 00 00 00 48 89 44 24 08 31 c0 48 8d 4c 24 07 48 c7 c6 80 
>> 8a 26 b5 <c7> 04 25 00 00 00 00 00 00 00 00 48 c7 87 70 01 00 00 a6 e9 
>> 8c b5
>> [    1.049204] RSP: 0000:ffffa609807c7ec8 EFLAGS: 00010246
>> [    1.049642] RAX: 0000000000000000 RBX: ffff91d982623000 RCX: 
>> ffffa609807c7ecf
>> [    1.050213] RDX: 0000000000000001 RSI: ffffffffb5268a80 RDI: 
>> ffffa60980013c68
>> [    1.050799] RBP: ffff91d98105afc0 R08: ffffffffb4567f50 R09: 
>> ffffffffb5807ce8
>> [    1.051375] R10: 0000000000000000 R11: 0000000000000001 R12: 
>> ffff91d98105afc0
>> [    1.051941] R13: ffff91d983c749c0 R14: ffffffffb45685e0 R15: 
>> ffff91d982623000
>> [    1.052543] FS:  0000000000000000(0000) GS:ffff91e48f9c0000(0000) 
>> knlGS:0000000000000000
>> [    1.053187] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [    1.053649] CR2: 0000000000000000 CR3: 00000004cee30000 CR4: 
>> 00000000000006f0
>> [    1.054214] Call Trace:
>> [    1.054427]  <TASK>
>> [    1.054597]  ? __die+0x1e/0x60
>> [    1.054844]  ? page_fault_oops+0x17b/0x4a0
>> [    1.055174]  ? search_extable+0x26/0x30
>> [    1.055482]  ? kunit_test_null_dereference+0x37/0x80
>> [    1.055888]  ? search_module_extables+0x14/0x50
>> [    1.056255]  ? exc_page_fault+0x6b/0x150
>> [    1.056571]  ? asm_exc_page_fault+0x26/0x30
>> [    1.056898]  ? __pfx_kunit_generic_run_threadfn_adapter+0x10/0x10
>> [    1.057387]  ? __pfx_kunit_fail_assert_format+0x10/0x10
>> [    1.057799]  ? kunit_test_null_dereference+0x37/0x80
>> [    1.058195]  ? __kthread_parkme+0x33/0x80
>> [    1.058523]  kunit_generic_run_threadfn_adapter+0x1c/0x40
>> [    1.058949]  kthread+0xe9/0x1f0
>> [    1.059206]  ? __pfx_kthread+0x10/0x10
>> [    1.059513]  ret_from_fork+0x2f/0x50
>> [    1.059798]  ? __pfx_kthread+0x10/0x10
>> [    1.060095]  ret_from_fork_asm+0x1a/0x30
>> [    1.060421]  </TASK>
>> [    1.060597] Modules linked in:
>> [    1.060841] CR2: 0000000000000000
>> [    1.061104] ---[ end trace 0000000000000000 ]---
>> [    1.061481] RIP: 0010:kunit_test_null_dereference+0x37/0x80
>>
>>
>> I attach my kernel config and the full log file.
>>
>> What's awkward is that it does not seem to be related directly to
>> sched, but only faults with sched.
>>
>>
>> Could you try to reproduce this, Tvrtko?
> 
> Any chance that between the two runs you somehow manage to enable 
> CONFIG_KUNIT_FAULT_TEST?

Hmm in the sea of kunit_test_null_dereference there was a drm sched 
related fail too. Investigating.

Regards,

Tvrtko

>>
>>
>> Thanks
>> P.
>>
>>
>>>
>>> v2:
>>>   * Parameterize a bunch of similar tests.
>>>   * Improve test commentary.
>>>   * Rename TDR test to timeout. (Christian)
>>>   * Improve quality and consistency of naming. (Philipp)
>>>
>>> RFC v2 -> series v1:
>>>   * Rebased for drm_sched_init changes.
>>>   * Fixed modular build.
>>>   * Added some comments.
>>>   * Filename renames. (Philipp)
>>>
>>> v2:
>>>   * Dealt with a bunch of checkpatch warnings.
>>>
>>> v3:
>>>   * Some mock API renames, kerneldoc grammar fixes and indentation
>>> fixes.
>>>
>>> Cc: Christian König <christian.koenig at amd.com>
>>> Cc: Danilo Krummrich <dakr at kernel.org>
>>> Cc: Matthew Brost <matthew.brost at intel.com>
>>> Cc: Philipp Stanner <phasta at kernel.org>
>>>
>>> Tvrtko Ursulin (5):
>>>    drm: Move some options to separate new Kconfig
>>>    drm/scheduler: Add scheduler unit testing infrastructure and some
>>>      basic tests
>>>    drm/scheduler: Add a simple timeout test
>>>    drm/scheduler: Add basic priority tests
>>>    drm/scheduler: Add a basic test for modifying entities scheduler
>>> list
>>>
>>>   drivers/gpu/drm/Kconfig                       | 109 +----
>>>   drivers/gpu/drm/Kconfig.debug                 | 115 +++++
>>>   drivers/gpu/drm/scheduler/.kunitconfig        |  12 +
>>>   drivers/gpu/drm/scheduler/Makefile            |   2 +
>>>   drivers/gpu/drm/scheduler/tests/Makefile      |   7 +
>>>   .../gpu/drm/scheduler/tests/mock_scheduler.c  | 323 +++++++++++++
>>>   drivers/gpu/drm/scheduler/tests/sched_tests.h | 223 +++++++++
>>>   drivers/gpu/drm/scheduler/tests/tests_basic.c | 426
>>> ++++++++++++++++++
>>>   8 files changed, 1113 insertions(+), 104 deletions(-)
>>>   create mode 100644 drivers/gpu/drm/Kconfig.debug
>>>   create mode 100644 drivers/gpu/drm/scheduler/.kunitconfig
>>>   create mode 100644 drivers/gpu/drm/scheduler/tests/Makefile
>>>   create mode 100644 drivers/gpu/drm/scheduler/tests/mock_scheduler.c
>>>   create mode 100644 drivers/gpu/drm/scheduler/tests/sched_tests.h
>>>   create mode 100644 drivers/gpu/drm/scheduler/tests/tests_basic.c
>>>
>>
> 