Am 11.03.25 um 18:13 schrieb Raag Jadav:
> On Mon, Mar 10, 2025 at 06:03:27PM -0400, Alex Deucher wrote:
>> On Mon, Mar 10, 2025 at 5:54 PM André Almeida <andrealm...@igalia.com> wrote:
>>> Em 01/03/2025 03:04, Raag Jadav escreveu:
>>>> On Fri, Feb 28, 2025 at 06:49:43PM -0300, André Almeida wrote:
>>>>> Hi Raag,
>>>>>
>>>>> On 2/28/25 11:58, Raag Jadav wrote:
>>>>>> On Fri, Feb 28, 2025 at 09:13:53AM -0300, André Almeida wrote:
>>>>>>> To notify userspace about which app (if any) made the device get in a
>>>>>>> wedge state, make use of drm_wedge_app_info parameter, filling it with
>>>>>>> the app PID and name.
>>>>>>>
>>>>>>> Signed-off-by: André Almeida <andrealm...@igalia.com>
>>>>>>> ---
>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 19 +++++++++++++++++--
>>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_job.c | 6 +++++-
>>>>>>> 2 files changed, 22 insertions(+), 3 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>>>> index 00b9b87dafd8..e06adf6f34fd 100644
>>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>>>> @@ -6123,8 +6123,23 @@ int amdgpu_device_gpu_recover(struct
>>>>>>> amdgpu_device *adev,
>>>>>>> atomic_set(&adev->reset_domain->reset_res, r);
>>>>>>> - if (!r)
>>>>>>> - drm_dev_wedged_event(adev_to_drm(adev),
>>>>>>> DRM_WEDGE_RECOVERY_NONE, NULL);
>>>>>>> + if (!r) {
>>>>>>> + struct drm_wedge_app_info aux, *info = NULL;
>>>>>>> +
>>>>>>> + if (job) {
>>>>>>> + struct amdgpu_task_info *ti;
>>>>>>> +
>>>>>>> + ti = amdgpu_vm_get_task_info_pasid(adev, job->pasid);
>>>>>>> + if (ti) {
>>>>>>> + aux.pid = ti->pid;
>>>>>>> + aux.comm = ti->process_name;
>>>>>>> + info = &aux;
>>>>>>> + amdgpu_vm_put_task_info(ti);
>>>>>>> + }
>>>>>>> + }
>>>>>> Is this guaranteed to be guilty app and not some scheduled worker?
>>>>> This is how amdgpu decides which app is the guilty one earlier in the code
>>>>> as in the print:
>>>>>
>>>>> ti = amdgpu_vm_get_task_info_pasid(ring->adev, job->pasid);
>>>>>
>>>>> "Process information: process %s pid %d thread %s pid %d\n"
>>>>>
>>>>> So I think it's consistent with what the driver thinks it's the guilty
>>>>> process.
>>>> Sure, but with something like app_info we're kind of hinting to userspace
>>>> that an application was _indeed_ involved with reset. Is that also
>>>> guaranteed?
>>>>
>>>> Is it possible that an application needlessly suffers from a false positive
>>>> scenario (reset due to other factors)?
>>>>
>>> I asked Alex Deucher in IRC about that and yes, there's a chance that
>>> this is a false positive. However, for the majority of cases this is the
>>> right app that caused the hang. This is what amdgpu is doing for GL
>>> robustness as well and devcoredump, so it's very consistent with how
>>> amdgpu deals with this scenario even if the mechanism is still not perfect.
>> It's usually the guilty one, but it's not guaranteed. For example,
>> say you have a ROCm user queue and a gfx job submitted to a kernel
>> queue. The actual guilty job may be the ROCm user queue, but the
>> driver may not detect that the ROCm queue was hung until some other
>> event (e.g., memory pressure). However, the timer for the gfx job may
>> timeout before that happens on the ROCm queue so in that case the gfx
>> job would be incorrectly considered guilty.
> So it boils down to what are the chances of that happening and whether
> it's significant enough to open the door for API abuse.
We are also working on an enforce_isolation parameter for amdgpu which only
allows one application at a time to use the hardware for the cost of
performance.
The problem is simply that when you don't allow multiple applications to use
the HW at the same time you also don't get full utilization of the different HW
blocks.
It can also be that a crash only happens because two applications do something
at the same time which is not supposed to happen at the same time. Those issue
are then usually fixed by firmware updates, but are really really hard to debug.
I don't see much potential for abuse here since you can't easily control from
userspace when a lockup happens. And the AMD Linux team has made quite a bunch
of requirements to the HW/FW engineers recently which should improve the
situation on future HW generations.
So I think we should probably just document that reliability of this
information is driver and hardware specific and should be taken with a grain of
salt and call it a day.
Regards,
Christian.
>
> Considering this is amd specific accuracy, it's still an open question
> how other drivers are/will be managing it.
>
> Raag
