Re: [PATCH v2 08/12] drm/amdgpu: use doorbell manager for kfd kernel doorbells

[Felix Kuehling <felix.kuehling@amd.com>]

On 2023-04-22 2:39, Shashank Sharma wrote:
> - KFD process level doorbells: doorbell pages which are allocated by 
> kernel but mapped and written by userspace processes, saved in struct 
> pdd->qpd->doorbells
>
> size = kfd_doorbell_process_slice.
>
> We realized that we only need 1-2 doorbells for KFD kernel level stuff 
> (so kept it one page), but need 2-page of doorbells for KFD process, 
> so they are sized accordingly.
>
> We have also run kfd_test_suit and verified the changes for any 
> regression. Hope this helps in explaining the design.

Right, I missed that this was only for kernel doorbells. I wonder 
whether KFD really needs its own page here. I think we only need a 
doorbell for HWS. And when we use MES, I think even that isn't needed 
because MES packet submissions go through amdgpu. So maybe KFD doesn't 
need its own kernel-mode doorbell page any more on systems with user 
graphics mode queues.

Regards,
   Felix


>
> - Shashank