Re: [PATCH 09/10] drm/amdgpu: add gang submit backend

[Andrey Grodzovsky <andrey.grodzovsky@amd.com>]

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On 2022-03-05 13:40, Christian König wrote:
> Am 04.03.22 um 18:10 schrieb Andrey Grodzovsky:
>>
>> On 2022-03-03 03:23, Christian König wrote:
>>> Allows submitting jobs as gang which needs to run on multiple
>>> engines at the same time.
>>>
>>> Basic idea is that we have a global gang submit fence representing 
>>> when the
>>> gang leader is finally pushed to run on the hardware last.
>>>
>>> Jobs submitted as gang are never re-submitted in case of a GPU reset 
>>> since this
>>> won't work and will just deadlock the hardware immediately again.
>>>
>>> Signed-off-by: Christian König <christian.koenig@amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu.h        |  3 ++
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 34 
>>> ++++++++++++++++++++++
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_job.c    | 28 ++++++++++++++++--
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_job.h    |  3 ++
>>>   4 files changed, 66 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>> index 7f447ed7a67f..a664d43d7502 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>> @@ -852,6 +852,7 @@ struct amdgpu_device {
>>>       u64                fence_context;
>>>       unsigned            num_rings;
>>>       struct amdgpu_ring        *rings[AMDGPU_MAX_RINGS];
>>> +    struct dma_fence __rcu        *gang_submit;
>>>       bool                ib_pool_ready;
>>>       struct amdgpu_sa_manager ib_pools[AMDGPU_IB_POOL_MAX];
>>>       struct amdgpu_sched 
>>> gpu_sched[AMDGPU_HW_IP_NUM][AMDGPU_RING_PRIO_MAX];
>>> @@ -1233,6 +1234,8 @@ void amdgpu_device_invalidate_hdp(struct 
>>> amdgpu_device *adev,
>>>           struct amdgpu_ring *ring);
>>>     void amdgpu_device_halt(struct amdgpu_device *adev);
>>> +struct dma_fence *amdgpu_device_switch_gang(struct amdgpu_device 
>>> *adev,
>>> +                        struct dma_fence *gang);
>>>     /* atpx handler */
>>>   #if defined(CONFIG_VGA_SWITCHEROO)
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> index d78141e2c509..a116b8c08827 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> @@ -3512,6 +3512,7 @@ int amdgpu_device_init(struct amdgpu_device 
>>> *adev,
>>>       adev->gmc.gart_size = 512 * 1024 * 1024;
>>>       adev->accel_working = false;
>>>       adev->num_rings = 0;
>>> +    RCU_INIT_POINTER(adev->gang_submit, dma_fence_get_stub());
>>>       adev->mman.buffer_funcs = NULL;
>>>       adev->mman.buffer_funcs_ring = NULL;
>>>       adev->vm_manager.vm_pte_funcs = NULL;
>>> @@ -3989,6 +3990,7 @@ void amdgpu_device_fini_sw(struct 
>>> amdgpu_device *adev)
>>>       release_firmware(adev->firmware.gpu_info_fw);
>>>       adev->firmware.gpu_info_fw = NULL;
>>>       adev->accel_working = false;
>>> + dma_fence_put(rcu_dereference_protected(adev->gang_submit, true));
>>>         amdgpu_reset_fini(adev);
>>>   @@ -5744,3 +5746,35 @@ void amdgpu_device_halt(struct 
>>> amdgpu_device *adev)
>>>       pci_disable_device(pdev);
>>>       pci_wait_for_pending_transaction(pdev);
>>>   }
>>> +
>>> +/**
>>> + * amdgpu_device_switch_gang - switch to a new gang
>>> + * @adev: amdgpu_device pointer
>>> + * @gang: the gang to switch to
>>> + *
>>> + * Try to switch to a new gang or return a reference to the current 
>>> gang if that
>>> + * isn't possible.
>>> + * Returns: Either NULL if we switched correctly or a reference to 
>>> the existing
>>> + * gang.
>>> + */
>>> +struct dma_fence *amdgpu_device_switch_gang(struct amdgpu_device 
>>> *adev,
>>> +                        struct dma_fence *gang)
>>> +{
>>> +    struct dma_fence *old = NULL;
>>> +
>>> +    do {
>>> +        dma_fence_put(old);
>>> +        old = dma_fence_get_rcu_safe(&adev->gang_submit);
>>> +
>>> +        if (old == gang)
>>> +            break;
>>> +
>>> +        if (!dma_fence_is_signaled(old))
>>> +            return old;
>>> +
>>> +    } while (cmpxchg((struct dma_fence __force **)&adev->gang_submit,
>>> +             old, gang) != old);
>>> +
>>> +    dma_fence_put(old);
>>> +    return NULL;
>>> +}
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
>>> index e07ceae36a5c..059e11c7898c 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
>>> @@ -169,11 +169,29 @@ static void amdgpu_job_free_cb(struct 
>>> drm_sched_job *s_job)
>>>           kfree(job);
>>>   }
>>>   +void amdgpu_job_set_gang_leader(struct amdgpu_job *job,
>>> +                struct amdgpu_job *leader)
>>> +{
>>> +    struct dma_fence *fence = &leader->base.s_fence->scheduled;
>>> +
>>> +    WARN_ON(job->gang_submit);
>>> +
>>> +    /*
>>> +     * Don't add a reference when we are the gang leader to avoid 
>>> circle
>>> +     * dependency.
>>> +     */
>>> +    if (job != leader)
>>> +        dma_fence_get(fence);
>>> +    job->gang_submit = fence;
>>> +}
>>> +
>>>   void amdgpu_job_free(struct amdgpu_job *job)
>>>   {
>>>       amdgpu_job_free_resources(job);
>>>       amdgpu_sync_free(&job->sync);
>>>       amdgpu_sync_free(&job->sched_sync);
>>> +    if (job->gang_submit != &job->base.s_fence->scheduled)
>>> +        dma_fence_put(job->gang_submit);
>>>         /* only put the hw fence if has embedded fence */
>>>       if (job->hw_fence.ops != NULL)
>>> @@ -247,12 +265,16 @@ static struct dma_fence 
>>> *amdgpu_job_dependency(struct drm_sched_job *sched_job,
>>>           fence = amdgpu_sync_get_fence(&job->sync);
>>>       }
>>>   +    if (!fence && !job->gang_submit)
>>> +        fence = amdgpu_device_switch_gang(ring->adev, 
>>> job->gang_submit);
>>> +
>>
>>
>> Why job->gang_submit should be NULL in the check above ? Don't you 
>> want to switch to an actual new gang fence here ?
>> Jobs that don't have gang_submit fence set are not gang jobs anyway 
>> and we don't care for this dependency
>> for them right ?
>
> Well exactly that's the point. That a job is not part of a gang submit 
> is signaled by setting the pointer to NULL.


No dispute on this


>
> If we don't check for NULL here we would just crash.


But you go into the 'if clause' if job->gang_submit is equal to NULL, i 
would expect to see here
if (!fence &&*job->gang_submit*) because you want to switch to an actual 
new gang (not to NULL)

Andrey


>
> Christian.
>
>>
>> Andrey
>>
>>
>>>       return fence;
>>>   }
>>>     static struct dma_fence *amdgpu_job_run(struct drm_sched_job 
>>> *sched_job)
>>>   {
>>>       struct amdgpu_ring *ring = to_amdgpu_ring(sched_job->sched);
>>> +    struct amdgpu_device *adev = ring->adev;
>>>       struct dma_fence *fence = NULL, *finished;
>>>       struct amdgpu_job *job;
>>>       int r = 0;
>>> @@ -264,8 +286,10 @@ static struct dma_fence *amdgpu_job_run(struct 
>>> drm_sched_job *sched_job)
>>>         trace_amdgpu_sched_run_job(job);
>>>   -    if (job->vram_lost_counter != 
>>> atomic_read(&ring->adev->vram_lost_counter))
>>> -        dma_fence_set_error(finished, -ECANCELED);/* skip IB as 
>>> well if VRAM lost */
>>> +    /* Skip job if VRAM is lost and never resubmit gangs */
>>> +    if (job->vram_lost_counter != 
>>> atomic_read(&adev->vram_lost_counter) ||
>>> +        (job->job_run_counter && job->gang_submit))
>>> +        dma_fence_set_error(finished, -ECANCELED);
>>>         if (finished->error < 0) {
>>>           DRM_INFO("Skip scheduling IBs!\n");
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.h 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.h
>>> index 0bab8fe0d419..615328130615 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.h
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.h
>>> @@ -51,6 +51,7 @@ struct amdgpu_job {
>>>       struct amdgpu_sync    sched_sync;
>>>       struct dma_fence    hw_fence;
>>>       struct dma_fence    *external_hw_fence;
>>> +    struct dma_fence    *gang_submit;
>>>       uint32_t        preamble_status;
>>>       uint32_t                preemption_status;
>>>       bool                    vm_needs_flush;
>>> @@ -80,6 +81,8 @@ int amdgpu_job_alloc_with_ib(struct amdgpu_device 
>>> *adev, unsigned size,
>>>   void amdgpu_job_set_resources(struct amdgpu_job *job, struct 
>>> amdgpu_bo *gds,
>>>                     struct amdgpu_bo *gws, struct amdgpu_bo *oa);
>>>   void amdgpu_job_free_resources(struct amdgpu_job *job);
>>> +void amdgpu_job_set_gang_leader(struct amdgpu_job *job,
>>> +                struct amdgpu_job *leader);
>>>   void amdgpu_job_free(struct amdgpu_job *job);
>>>   int amdgpu_job_submit(struct amdgpu_job *job, struct 
>>> drm_sched_entity *entity,
>>>                 void *owner, struct dma_fence **f);
>

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