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

["Christian König" <christian.koenig@amd.com>]

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Am 07.03.22 um 16:40 schrieb Andrey Grodzovsky:
>
> 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)
>

WTF? I'm like 100% that I've fixed that before sending it out.

Thanks for point it out, but yeah I've already stumbled over that typo 
as well.

Christian.

> 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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