Re: [PATCH RFC v6 05/26] nova-core: mm: Add support to use PRAMIN windows to write to VRAM

John Hubbard
2026-01-31T03:21:35Z

On 1/30/26 7:00 PM, Dave Airlie wrote:
> On Sat, 31 Jan 2026 at 07:14, Joel Fernandes <joelagnelf@nvidia.com> wrote:
>> On 1/29/2026 10:38 PM, John Hubbard wrote:
>>> On 1/29/26 5:59 PM, Joel Fernandes wrote:
>>>> On 1/29/26 8:12 PM, John Hubbard wrote:
>>>>> On 1/29/26 4:26 PM, Joel Fernandes wrote:
>>>>>> [...]
>> Will work on these issues for the v7. Thanks,
>
> The way this works on nouveau at least (and I haven't yet read the
> nova code in depth).
>
> Is we have 4 stages of vmm page table mgmt.
>
> ref - locked with a ref lock - can allocate/free memory - just makes
> sure the page tables exist and are reference counted
> map - locked with a map lock - cannot allocate memory - fill in the
> PTEs in the page table
> unmap - locked with a map lock - cannot allocate memory - removes
> entries in PTEs
> unref - locked with a ref lock - can allocate/free memory - just drops
> references and frees (not sure if it ever merges).
>
> So maps and unmaps can be in fence signalling paths, but unrefs are
> done in free job from a workqueue.
>

Nice! Thanks Dave, I guess this is one time we really should have
taken a peek at nouveau for inspiration after all. :)

thanks,
--
John Hubbard