[PATCH v5] drm/test: add a test suite for GEM objects backed by shmem
Guenter Roeck
linux at roeck-us.net
Thu Feb 22 15:52:26 UTC 2024
Hi Marco,
On 2/22/24 07:32, Marco Pagani wrote:
>
>
> On 2024-02-18 16:49, Guenter Roeck wrote:
>> Hi,
>>
>> On Thu, Nov 30, 2023 at 06:14:16PM +0100, Marco Pagani wrote:
>>> This patch introduces an initial KUnit test suite for GEM objects
>>> backed by shmem buffers.
>>>
>>> Suggested-by: Javier Martinez Canillas <javierm at redhat.com>
>>> Signed-off-by: Marco Pagani <marpagan at redhat.com>
>>
>> When running this in qemu, I get lots of warnings backtraces in the drm
>> core.
>>
>> WARNING: CPU: 0 PID: 1341 at drivers/gpu/drm/drm_gem_shmem_helper.c:327
>> WARNING: CPU: 0 PID: 1341 at drivers/gpu/drm/drm_gem_shmem_helper.c:173
>> WARNING: CPU: 0 PID: 1341 at drivers/gpu/drm/drm_gem_shmem_helper.c:385
>> WARNING: CPU: 0 PID: 1341 at drivers/gpu/drm/drm_gem_shmem_helper.c:211
>> WARNING: CPU: 0 PID: 1345 at kernel/dma/mapping.c:194
>> WARNING: CPU: 0 PID: 1347 at drivers/gpu/drm/drm_gem_shmem_helper.c:429
>> WARNING: CPU: 0 PID: 1349 at drivers/gpu/drm/drm_gem_shmem_helper.c:445
>>
>> It looks like dma_resv_assert_held() asserts each time it is executed.
>> The backtrace in kernel/dma/mapping.c is triggered by
>> if (WARN_ON_ONCE(!dev->dma_mask))
>> return 0;
>> in __dma_map_sg_attrs().
>>
>> Is this a possible problem in the test code, or can it be caused by
>> some limitations or bugs in the qemu emulation ? If so, do you have any
>> thoughts or ideas what those limitations / bugs might be ?
>
> Hi Guenter,
>
> Thanks for reporting this issue. As you correctly noted, the warnings appear to
> be caused by the dma_mask in the mock device being uninitialized. I'll send a
> patch to fix it soon.
>
Thanks a lot for the update.
In this context, the TTM unit tests fail as well in qemu, with worse result:
It seems there is some bad cleanup after a failed test case, causing list
corruptions in the drm core and ultimately a crash. I don't know if this
is also caused by the missing dma_mask initialization.
Thanks,
Guenter
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