[Intel-gfx] [PATCH] drm/i915/ttm: consider all placements for the page alignment

[Matthew Auld]

On Tue, 22 Jun 2021 at 11:11, Thomas Hellström
<thomas.hellstrom at linux.intel.com> wrote:
>
>
> On 6/22/21 11:58 AM, Matthew Auld wrote:
> > Just checking the current region is not enough, if we later migrate the
> > object somewhere else. For example if the placements are {SMEM, LMEM},
> > then we might get this wrong. Another idea might be to make the
> > page_alignment part of the ttm_place, instead of the BO.
> >
> > Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> > Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> > ---
> >   drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 21 ++++++++++++++++++++-
> >   1 file changed, 20 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> > index c5deb8b7227c..5d894bba6430 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> > @@ -753,6 +753,25 @@ void i915_ttm_bo_destroy(struct ttm_buffer_object *bo)
> >               call_rcu(&obj->rcu, __i915_gem_free_object_rcu);
> >   }
> >
> > +static u64 i915_gem_object_page_size(struct drm_i915_gem_object *obj)
> > +{
> > +     u64 page_size;
> > +     int i;
> > +
> > +     if (!obj->mm.n_placements)
> > +             return obj->mm.region->min_page_size;
> > +
> > +     page_size = 0;
> > +     for (i = 0; i < obj->mm.n_placements; i++) {
> > +             struct intel_memory_region *mr = obj->mm.placements[i];
> > +
> > +             page_size = max_t(u64, mr->min_page_size, page_size);
> > +     }
> > +
> > +     GEM_BUG_ON(!page_size);
> > +     return page_size;
> > +}
> > +
> >   /**
> >    * __i915_gem_ttm_object_init - Initialize a ttm-backed i915 gem object
> >    * @mem: The initial memory region for the object.
> > @@ -793,7 +812,7 @@ int __i915_gem_ttm_object_init(struct intel_memory_region *mem,
> >       obj->base.vma_node.driver_private = i915_gem_to_ttm(obj);
> >       ret = ttm_bo_init(&i915->bdev, i915_gem_to_ttm(obj), size,
> >                         bo_type, &i915_sys_placement,
> > -                       mem->min_page_size >> PAGE_SHIFT,
> > +                       i915_gem_object_page_size(obj) >> PAGE_SHIFT,
>
> Hmm, can't we just have the buddy manager silently enforce its
> min_page_size?

Maybe, but we need some way of overriding it for all of our page-table
allocations(and some other stuff also), so being able to control the
page_alignment at the object level here seems reasonable? Could maybe
pass it through with create_lmem_with_page_size(..., page_size)? Ok,
it might be best to first type it and then see how it will all fit
together.


>
> /Thomas
>
>
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