Re: [PATCH] dmr/amdgpu: Fix wrongly unref of BO

[Felix Kuehling <felix.kuehling-5C7GfCeVMHo@public.gmane.org>]

On 17-04-21 01:01 PM, Christian König wrote:
> Am 21.04.2017 um 17:43 schrieb Felix Kuehling:
>> On 17-04-21 03:11 AM, Christian König wrote:
>>> Hi Alex,
>>>
>>>> No. For the current source code, I think the premap and no-op is not
>>>> working.
>>>>
>>> Indeed, we don't set bo->mem.bus.addr in amdgpu_ttm_io_mem_reserve()
>>> any more. Felix will probably want to fix that for the KFD branch.
>> I vaguely remember discussing this in the past: using mem->bus.addr to
>> keep memory permanently CPU-mapped and avoid redundant ioremap calls. As
>> I remember it, we weren't actually using this. It's only something we
>> considered at one point.
>
> Well that explains why my memory fooled me.
>
> My last status was that we implemented this together with CPU based
> page table updates.
>
> Otherwise mapping them for CPU access is rather heavy if we indeed
> update the page tables every time.

We also don't currently have CPU page table updates for KFD. When we
rebased on 4.9, the VM code was restructured so much that we essentially
had to go back and reimplement it. Harish is working on this right now.

Regards,
  Felix

>
> Christian.
>

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