[PATCH 2/2] drm/amdgpu: Let KFD use more VMIDs on Arcturus

[Felix Kuehling]

Am 2020-06-25 um 11:38 a.m. schrieb Christian König:
> Am 25.06.20 um 17:15 schrieb Felix Kuehling:
>> Am 2020-06-25 um 4:19 a.m. schrieb Christian König:
>>> Am 25.06.20 um 05:18 schrieb Felix Kuehling:
>>>> When there is no graphics support, KFD can use more of the VMIDs.
>>>> Graphics
>>>> VMIDs are only used for video decoding/encoding and post processing.
>>>> With
>>>> two VCE engines, there is no reason to reserve more than 2 VMIDs for
>>>> that.
>>> IIRC the expectation is that we still use the compute queues for post
>>> processing and not the KFD.
>>>
>>> So we will need at least VMIDs for that as well.
>> Correct. Post processing uses compute queues and VMIDs in the GFXHUB.
>> VCE uses VMIDs in the MMHUB. I believe in Mesa they use the same VM
>> context. So can't they share the same VMIDs?
>
> Ah! Good point, But we still need at least 3 VMID when VMID
> reservation is active.

I don't know anything about that VMID reservation feature. What is it
used for? Who is using it? How many VMIDs can be reserved?

If one VMID is reserved, there would still be one VMID left for video
post processing. That's not ideal, but I don't think it would be fatal.
But is it a realistic use case that VMID reservation and ROCm+video
processing would happen on the same system at the same time?

Thanks,
  Felix


>
> I don't think you can go below this.
>
> Regards,
> Christian.
>
>>
>> Regards,
>>    Felix
>>
>>
>>>> Signed-off-by: Felix Kuehling <Felix.Kuehling at amd.com>
>>>> ---
>>>>    drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c | 11 ++++++++---
>>>>    1 file changed, 8 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c
>>>> b/drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c
>>>> index 6e10b42c57e5..3470929e5b8e 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c
>>>> @@ -1245,10 +1245,15 @@ static int gmc_v9_0_sw_init(void *handle)
>>>>        /*
>>>>         * number of VMs
>>>>         * VMID 0 is reserved for System
>>>> -     * amdgpu graphics/compute will use VMIDs 1-7
>>>> -     * amdkfd will use VMIDs 8-15
>>>> +     * amdgpu graphics/compute will use VMIDs 1..n-1
>>>> +     * amdkfd will use VMIDs n..15
>>>> +     *
>>>> +     * The first KFD VMID is 8 for GPUs with graphics, 3 for
>>>> +     * compute-only GPUs. On compute-only GPUs that leaves 2 VMIDs
>>>> +     * for video processing.
>>>>         */
>>>> -    adev->vm_manager.first_kfd_vmid = 8;
>>>> +    adev->vm_manager.first_kfd_vmid =
>>>> +        adev->asic_type == CHIP_ARCTURUS ? 3 : 8;
>>>>          amdgpu_vm_manager_init(adev);
>>>>    
>