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Question below. > On Thu, Aug 20, 2026 at 10:34:49PM -0400, Nathan Bourgeois wrote: > > > 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. > > > > > For Xe I believe Thomas and I aligned a xe_bo_validate with a correct > xe_validation_guard is the Xe preferred solution in the existing > design... But a question to Dave below before I commit to anything. > > > Nathan > > > > On Thu, Aug 20, 2026 at 9:08 PM Dave Airlie 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: > > We don't charge any cgroups yet, right? This would only come into play > once a version of [1] merges, correct? > > What would prevent the pages populated for a TTM BO from being > immediately reclaimed and discarded? I'm fairly certain Xe's shrinker > could do exactly that, since we don't pin those pages. This seems to > imply that we'd need to store the cgroup associated with the TTM BO at > creation time and charge allocations to that cgroup, regardless of which > task ultimately triggers the page allocation. > > Another option, instead of validating, is to revert > ttm_bo_setup_export() entirely and rethink the overall approach as part > of [1]. > > Matt > > [1] https://patchwork.freedesktop.org/series/169831/ > > > > Dave.