[PATCH 3/8] drm/amdgpu: Implement mmap as GEM object function

[Felix Kuehling]

On 2021-04-07 3:34 p.m., Felix Kuehling wrote:
> On 2021-04-07 7:25 a.m., Christian König wrote:
>>>>>> +    /*
>>>>>> +     * Don't verify access for KFD BOs. They don't have a GEM
>>>>>> +     * object associated with them.
>>>>>> +     */
>>>>>> +    if (bo->kfd_bo)
>>>>>> +        goto out;
>>>>> Who does the access verification now?
>>>> This is somewhat confusing.
>>>>
>>>> I took this check as-is, including the comment, from amdgpu's
>>>> verify_access function. The verify_access function was called by
>>>> ttm_bo_mmap. It returned 0 and ttm_bo_mmap did the mapping.
>>> This is probably a left-over from when we mapped BOs using /dev/kfd. We
>>> changed this to use /dev/dri/renderD* a long time ago to fix CPU 
>>> mapping
>>> invalidations on memory evictions. I think we can let GEM do the access
>>> check.
>>
>> Ok, good to know.
>>
>> Thomas can you remove the extra handling in a separate prerequisite 
>> patch?
>>
>> If anybody then bisects to this patch we at least know what to do to 
>> get it working again.
>
> FWIW, I ran KFDTest test with this shortcut removed on current 
> amd-staging-drm-next + my HMM patch series, and it didn't seem to 
> cause any issues.

Wait, I celebrated too soon. I was running the wrong kernel. I do see 
some failures where access is being denied. I need to do more debugging 
to figure out what's causing that.

Regards,
   Felix


>
> Regards,
>   Felix
>
>
>>
>> Regards,
>> Christian.