Re: [PATCH 1/2] drm/gpuvm: add deferred vm_bo cleanup

[Danilo Krummrich <dakr@kernel.org>]

On 9/8/25 2:11 PM, Boris Brezillon wrote:
> On Mon, 08 Sep 2025 13:11:32 +0200
> "Danilo Krummrich" <dakr@kernel.org> wrote:
>> I'm saying exactly what you say: "has to be a special unlink function" ->
>> drm_gpuva_unlink_defer_put(). :)
> 
> I don't see how calling drm_gpuva_unlink() instead of
> drm_gpuva_unlink_defer_put() would leak the vm_bo though.

Initially (i.e. a few mails back), it sounded to me as if you'd propose to drop
the drm_gpuva's vm_bo reference only when it is freed.

>> No, drivers can't iterate the evict/extobj lists directly; or at least this is
>> not intended by GPUVM's API and if drivers do so, this is considered peeking
>> into GPUVM internals, so drivers are on their own anyways.
>>
>> Iterators, such as for_each_vm_bo_in_list() are not exposed to drivers.
> 
> Okay, that's a good thing. I thought Xe was doing some funky stuff with
> the list...

Maybe, I don't know. If they do so, the should send patches adding the
corresponding iterators and provide a rationale why drivers need to access those
lists directly and why we can't provide an API that handles the overall
use-case, such as drm_gpuvm_prepare_objects(), etc.