Re: [PATCH 1/5] drm/i915: Allow i915 to manage the vma offset nodes instead of drm core

[Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>]

Quoting Abdiel Janulgue (2019-08-26 13:20:58)
> @@ -641,10 +642,18 @@ static void revoke_mmaps(struct intel_gt *gt)
>                 GEM_BUG_ON(vma->fence != &gt->ggtt->fence_regs[i]);
>                 node = &vma->obj->base.vma_node;
>                 vma_offset = vma->ggtt_view.partial.offset << PAGE_SHIFT;
> -               unmap_mapping_range(gt->i915->drm.anon_inode->i_mapping,
> +
> +               list_for_each_entry(mmo, &vma->obj->mmap_offsets, offset) {
> +                       node = &mmo->vma_node;
> +                       if (!drm_mm_node_allocated(&node->vm_node) ||
> +                           mmo->mmap_type != I915_MMAP_TYPE_GTT)
> +                               continue;

That list needs locking as is not protected by the reset srcu (and you
are not allowed your own locking in here, unless you have a jolly good
reason and can prove it will never block a reset).

One thing to observe is is that you only ever need the mmo associated
with a fence for revocation upon reset, and you could use a local list
for tracking the active mmo.
-Chris
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