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

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

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.

Regards,
   Felix


>
> Regards,
> Christian. 
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