[Intel-gfx] [PATCH] drm/i915: round_up the size to the alignment value

[Matthew Auld]

On Mon, 14 Mar 2022 at 19:32, Arunpravin
<Arunpravin.PaneerSelvam at amd.com> wrote:
>
> handle instances when size is not aligned with the min_page_size.
> Unigine Heaven has allocation requests for example required pages
> are 161 and alignment request is 128. To allocate the left over
> 33 pages, continues the iteration to find the order value which
> is 5 and 0 and when it compares with min_order = 7, triggers the
> BUG_ON((order < min_order). To avoid this problem, round_up the
> size to the alignment and enable the is_contiguous variable and
> the block trimmed to the original size.
>
> Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam at amd.com>
> ---
>  drivers/gpu/drm/i915/i915_ttm_buddy_manager.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
> index 129f668f21ff..318aa731de5b 100644
> --- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
> +++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
> @@ -40,6 +40,7 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
>         struct i915_ttm_buddy_resource *bman_res;
>         struct drm_buddy *mm = &bman->mm;
>         unsigned long n_pages, lpfn;
> +       bool is_contiguous = 0;
>         u64 min_page_size;
>         u64 size;
>         int err;
> @@ -48,6 +49,9 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
>         if (!lpfn)
>                 lpfn = man->size;
>
> +       if (place->flags & TTM_PL_FLAG_CONTIGUOUS)
> +               is_contiguous = 1;
> +
>         bman_res = kzalloc(sizeof(*bman_res), GFP_KERNEL);
>         if (!bman_res)
>                 return -ENOMEM;
> @@ -71,7 +75,12 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
>
>         GEM_BUG_ON(min_page_size < mm->chunk_size);
>
> -       if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
> +       if (!is_contiguous && !IS_ALIGNED(size, min_page_size)) {
> +               size = round_up(size, min_page_size);
> +               is_contiguous = 1;
> +       }
> +
> +       if (is_contiguous) {

This looks like it will also do roundup_power_of_two()? I assume we
instead just want to feed the list_last_entry() block for trimming?

Anway, we should be able to just make this:

if (WARN_ON(!IS_ALIGNED(size, min_page_size))
    return -EINVAL;

That's at least the currently expected behaviour in i915, just that we
were previously not verifying it here.

>                 unsigned long pages;
>
>                 size = roundup_pow_of_two(size);
> @@ -106,7 +115,7 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
>         if (unlikely(err))
>                 goto err_free_blocks;
>
> -       if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
> +       if (is_contiguous) {
>                 u64 original_size = (u64)bman_res->base.num_pages << PAGE_SHIFT;
>
>                 mutex_lock(&bman->lock);
>
> base-commit: b37605de46fef48555bf0cf463cccf355c51fac0
> --
> 2.25.1
>