[RFC PATCH 3/5] drm/amdgpu: Allow explicit sync for VM ops.

[Christian König]

Am 17.06.22 um 15:03 schrieb Bas Nieuwenhuizen:
> [SNIP]
>>>> BOOKKEEP can only be used by VM updates themselves. So that they don't
>>>> interfere with CS.
>>> That is the point why we would go BOOKKEEP for explicit sync CS
>>> submissions, no? Explicit submission shouldn't interfere with any
>>> other CS submissions. That includes being totally ignored by GL
>>> importers (if we want to have synchronization there between an
>>> explicit submission and GL, userspace is expected to use Jason's
>>> dmabuf fence import/export IOCTLs)
>> No, that would break existing DMA-buf rules.
>>
>> Explicit CS submissions are still a dependency for implicit submissions.
> This is explicitly what we don't want for explicit submissions and why
> I waited with this series until the DMA_RESV_USAGE series landed. We
> wish to opt out from implicit sync completely, and just use the IOCTLs
> Jason wrote for back-compat with windowing systems that need it.
>
> If BOOKKEEP isn't for that, should we add a new USAGE?

BOOKKEEP is exactly for that, but as discussed with Daniel that's not 
what we want in the kernel.

When you mix implicit with explicit synchronization (OpenGL with RADV 
for example) it should be mandatory for the OpenGL to wait for any RADV 
submission before issuing an operation.

What you want to do is intentionally not supported.

Regards,
Christian.