Re: [PATCH] drm/xe: Fix unnecessary host-side population of ttm_tt on non-TT resources

[Nathan Bourgeois]

> Shouldn't we just be calling xe_bo_validate() here instead of
> ttm_tt_populate? (With the correct xe_validation_guard() wrapping).

> Yes, this might be a better solution, making ttm_bo_setup_export()
> completely unnecessary.

If ttm_bo_setup_export() is unnecessary, I'm happy to change the patch
or make a new patch. I will attempt to implement and test this locally.

> This part looks good as different patch from what I'm assuming will be a
> TTM fix.

Regarding this, what do you recommend I do, assuming the patch
remains local to drm/xe? I'm still learning the ropes of contributing.

Nathan

On Thu, Aug 20, 2026 at 9:08 PM Dave Airlie <airlied@xxxxxxxxx> wrote:
>
> > Yes, this might be a better solution, making ttm_bo_setup_export()
> > completely unnecessary.
> >
> > It's also a bit odd that, in flows where we don't have backing storage
> > on export, we populate with pages and charge the system memory cgroup,
> > only to move the data to VRAM when the import attach is triggered,
> > resulting in a copy and a change in cgroup charging.
> >
> > I guess the question is why was ttm_bo_setup_export() introduced over
> > just a validation at export?
> >
>
> I'd like to think I had an answer for that, but I don't. Likely
> because I wasn't thinking about VRAM charging at all, and just
> worrying about making sure we had populated some pages for system
> memory ones, so the other side couldn't DoS us.
>
> Dave.