On Fri, Jul 16, 2021 at 8:54 AM Matthew Auld <matthew.william.auld@xxxxxxxxx> wrote: > > On Thu, 15 Jul 2021 at 23:39, Jason Ekstrand <jason@xxxxxxxxxxxxxx> wrote: > > > > Whenever we had a user object (n_placements > 0), we were ignoring > > obj->mm.region and always putting obj->placements[0] as the requested > > region. For LMEM+SMEM objects, this was causing them to get shoved into > > LMEM on every i915_ttm_get_pages() even when SMEM was requested by, say, > > i915_gem_object_migrate(). > > i915_ttm_migrate calls i915_ttm_place_from_region() directly with the > requested region, so there shouldn't be an issue with migration right? > Do you have some more details? With i915_ttm_migrate directly, no. But, in the last patch in the series, we're trying to migrate LMEM+SMEM buffers into SMEM on attach() and pin it there. This blows up in a very unexpected (IMO) way. The flow goes something like this: - Client attempts a dma-buf import from another device - In attach() we call i915_gem_object_migrate() which calls i915_ttm_migrate() which migrates as requested. - Once the migration is complete, we call i915_gem_object_pin_pages() which calls i915_ttm_get_pages() which depends on i915_ttm_placement_from_obj() and so migrates it right back to LMEM. Maybe the problem here is actually that our TTM code isn't respecting obj->mm.pages_pin_count? In case you can't tell, I really have no clue what I'm doing here. I'm really stumbling around in the dark finding things that make my bug go away. I'm happy for the feedback. --Jason > > > > > Signed-off-by: Jason Ekstrand <jason@xxxxxxxxxxxxxx> > > Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx> > > Cc: Matthew Auld <matthew.auld@xxxxxxxxx> > > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > > --- > > drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c > > index d30f274c329c7..5985e994d56cf 100644 > > --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c > > +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c > > @@ -150,8 +150,7 @@ i915_ttm_placement_from_obj(const struct drm_i915_gem_object *obj, > > unsigned int i; > > > > placement->num_placement = 1; > > - i915_ttm_place_from_region(num_allowed ? obj->mm.placements[0] : > > - obj->mm.region, requested, flags); > > + i915_ttm_place_from_region(obj->mm.region, requested, flags); > > > > /* Cache this on object? */ > > placement->num_busy_placement = num_allowed; > > -- > > 2.31.1 > >
