[Intel-gfx] [PATCH v2 03/16] drm/i915: Remove pages_mutex and intel_gtt->vma_ops.set/clear_pages members, v2.

[Matthew Auld]

On Mon, 29 Nov 2021 at 13:57, Maarten Lankhorst
<maarten.lankhorst at linux.intel.com> wrote:
>
> Big delta, but boils down to moving set_pages to i915_vma.c, and removing
> the special handling, all callers use the defaults anyway. We only remap
> in ggtt, so default case will fall through.
>
> Because we still don't require locking in i915_vma_unpin(), handle this by
> using xchg in get_pages(), as it's locked with obj->mutex, and cmpxchg in
> unpin, which only fails if we race a against a new pin.
>
> Changes since v1:
> - aliasing gtt sets ZERO_SIZE_PTR, not -ENODEV, remove special case
>   from __i915_vma_get_pages(). (Matt)
>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>

<snip>

> +static int
> +__i915_vma_get_pages(struct i915_vma *vma)
> +{
> +       struct sg_table *pages;
> +       int ret;
> +
> +       /*
> +        * The vma->pages are only valid within the lifespan of the borrowed
> +        * obj->mm.pages. When the obj->mm.pages sg_table is regenerated, so
> +        * must be the vma->pages. A simple rule is that vma->pages must only
> +        * be accessed when the obj->mm.pages are pinned.
> +        */
> +       GEM_BUG_ON(!i915_gem_object_has_pinned_pages(vma->obj));
> +
> +       switch (vma->ggtt_view.type) {
> +       default:
> +               GEM_BUG_ON(vma->ggtt_view.type);
> +               fallthrough;
> +       case I915_GGTT_VIEW_NORMAL:
> +               pages = vma->obj->mm.pages;
> +               break;
> +
> +       case I915_GGTT_VIEW_ROTATED:
> +               pages =
> +                       intel_rotate_pages(&vma->ggtt_view.rotated, vma->obj);
> +               break;
> +
> +       case I915_GGTT_VIEW_REMAPPED:
> +               pages =
> +                       intel_remap_pages(&vma->ggtt_view.remapped, vma->obj);
> +               break;
> +
> +       case I915_GGTT_VIEW_PARTIAL:
> +               pages = intel_partial_pages(&vma->ggtt_view, vma->obj);
> +               break;
> +       }
> +
> +       ret = 0;
> +       if (IS_ERR(pages)) {
> +               ret = PTR_ERR(pages);
> +               pages = NULL;
> +               drm_err(&vma->vm->i915->drm,
> +                       "Failed to get pages for VMA view type %u (%d)!\n",
> +                       vma->ggtt_view.type, ret);
> +       }
> +
> +       pages = xchg(&vma->pages, pages);
> +
> +       /* did we race against a put_pages? */
> +       if (pages && pages != vma->obj->mm.pages) {
> +               sg_free_table(vma->pages);
> +               kfree(vma->pages);

So should this one rather be:

sg_free_table(pages);
kfree(pages);

Or am I missing something?