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

[Dave Airlie]

> 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.