Re: [PATCH v10 12/21] gpu: nova-core: mm: Add unified page table entry wrapper enums

John Hubbard
2026-04-13T22:50:54Z

On 4/13/26 3:27 PM, Joel Fernandes wrote:
>
>
> On 4/13/2026 4:10 PM, Joel Fernandes wrote:
>> Hi Danilo,
>>
>> On 4/9/2026 7:00 AM, Danilo Krummrich wrote:
>>> On Thu Apr 9, 2026 at 12:33 PM CEST, Joel Fernandes wrote:
>>>> Since it is 3 against 1 here, I rest my case :-).
>>>
>>> That's not how I'd view it. :)
>>>
>>> Anyways, in case I'm included in "3", that's not my position. My point was to
>>> ensure we keep discussing advantages and disadvantages on their merits, as I
>>> think you both have good points.
>>
>> Heh, yes I actually *did not* include you in the 3 since you sounded to be open
>> to both. ;-)
>>
>>>
>>>> I am still in disagreement since I do not see much benefit (that is why I said
>>>> pointless above).
>>>
>>> That is fair -- in this case please explain why the advantages pointed out by
>>> others are not worth it, propose something that picks up the best of both
>>> worlds, etc.
>>>
>>> You can also turn it around and ask people whether they can tweak their counter
>>> proposal to get rid of specific parts you dislike for a reason.
>>>
>>> IOW, keep the ball rolling, so we can come up with the best possible solution.
>>
>> Good advice, thanks! I will try to come up with something that is acceptable to
>> everyone and we can further debate pros/cons on v11.
>>
>> There are some merits on the alternative proposal from Eliot/Alex that I'd like
>> to explore while seeing if I can keep some of the merits in mine as well.
> I think I found a nice approach. IMO the MMU version dispatch does not belong in
> Vmm/BarUser layers. Those are version-independent code. However I agree that
> doing version dispatch at every low-level page table operation is a bit heavy on
> matches (if we put the MMIO overhead counter-argument aside).
>
> So how about the following approach?
>
> PtWalk, PtMap and everything below it are monomorphized. Vmm and BarUser are
> not. Version dispatch is handled on PtWalk and PtMap entry points.

Conceptually it sounds pretty good.

>
> I think it makes it cleaner and splits the code up better too and the
> organizations makes sense because the version differences are related to page
> tables, not to generic concepts like Vmm and Bar.
>
> Thoughts? Here is a preview:
> https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git/commit/?h=pt-traits-v2&id=ff22ba64f729f9f73258777231763a7b9804123b
>

Probably impractical to review that here, so let's do the review in
a v11 posting, I think.

thanks,
--
John Hubbard