Re: [PATCH] drm/i915/gtt: Allow mixed pages to setup large PTE

[Matthew Auld <matthew.william.auld@gmail.com>]

On Fri, 26 Oct 2018 at 16:16, Chris Wilson <chris@chris-wilson.co.uk> wrote:
>
> For example, we may want to split a 2MiB large page into multiple 64KiB
> PTEs. To do so, we want to allow a vma that only has the 2MiB flag set
> to utilise the 64KiB as required, i.e. we want to include all larger
> pages as well.

I thought if we have vma that only has the 2M flag, that can only mean
that 64K is not supported by the platform?

>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Matthew Auld <matthew.auld@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem_gtt.c         |  4 ++--
>  drivers/gpu/drm/i915/selftests/huge_pages.c | 17 +++++++++++------
>  2 files changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 19b2d991b5d8..9e1756216ada 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -1074,7 +1074,7 @@ static void gen8_ppgtt_insert_huge_entries(struct i915_vma *vma,
>                 gen8_pte_t *vaddr;
>                 u16 index, max;
>
> -               if (vma->page_sizes.sg & I915_GTT_PAGE_SIZE_2M &&
> +               if (vma->page_sizes.sg & -I915_GTT_PAGE_SIZE_2M &&
>                     IS_ALIGNED(iter->dma, I915_GTT_PAGE_SIZE_2M) &&
>                     rem >= I915_GTT_PAGE_SIZE_2M && !idx.pte) {
>                         index = idx.pde;
> @@ -1092,7 +1092,7 @@ static void gen8_ppgtt_insert_huge_entries(struct i915_vma *vma,
>                         page_size = I915_GTT_PAGE_SIZE;
>
>                         if (!index &&
> -                           vma->page_sizes.sg & I915_GTT_PAGE_SIZE_64K &&
> +                           vma->page_sizes.sg & -I915_GTT_PAGE_SIZE_64K &&

Yeah, so here what if the platform doesn't support 64K pages, but does
support say 2M, and the object is 2M + 64K or perhaps it's 2M but
somehow only aligned to 64K? I think we exercise something like that
for the mock device, or at least I hope we do.

>                             IS_ALIGNED(iter->dma, I915_GTT_PAGE_SIZE_64K) &&
>                             (IS_ALIGNED(rem, I915_GTT_PAGE_SIZE_64K) ||
>                              rem >= (max - index) * I915_GTT_PAGE_SIZE))
> diff --git a/drivers/gpu/drm/i915/selftests/huge_pages.c b/drivers/gpu/drm/i915/selftests/huge_pages.c
> index 256001b00e32..2d66f380ad9a 100644
> --- a/drivers/gpu/drm/i915/selftests/huge_pages.c
> +++ b/drivers/gpu/drm/i915/selftests/huge_pages.c
> @@ -508,6 +508,7 @@ static int igt_mock_ppgtt_misaligned_dma(void *arg)
>                         goto out_unpin;
>                 }
>
> +               GEM_BUG_ON(vma->page_sizes.gtt);
>                 err = i915_vma_pin(vma, 0, 0, flags);
>                 if (err) {
>                         i915_vma_close(vma);
> @@ -517,8 +518,9 @@ static int igt_mock_ppgtt_misaligned_dma(void *arg)
>
>                 err = igt_check_page_sizes(vma);
>
> -               if (vma->page_sizes.gtt != page_size) {
> -                       pr_err("page_sizes.gtt=%u, expected %u\n",
> +               if (!(vma->page_sizes.gtt & -page_size)) {
> +                       pr_err("%s:%d page_sizes.gtt=%u, expected %u\n",
> +                              __func__, __LINE__,
>                                vma->page_sizes.gtt, page_size);
>                         err = -EINVAL;
>                 }
> @@ -542,6 +544,7 @@ static int igt_mock_ppgtt_misaligned_dma(void *arg)
>                                 goto out_unpin;
>                         }
>
> +                       GEM_BUG_ON(vma->page_sizes.gtt);
>                         err = i915_vma_pin(vma, 0, 0, flags | offset);
>                         if (err) {
>                                 i915_vma_close(vma);
> @@ -550,8 +553,9 @@ static int igt_mock_ppgtt_misaligned_dma(void *arg)
>
>                         err = igt_check_page_sizes(vma);
>
> -                       if (vma->page_sizes.gtt != I915_GTT_PAGE_SIZE_4K) {
> -                               pr_err("page_sizes.gtt=%u, expected %llu\n",
> +                       if (!(vma->page_sizes.gtt & -I915_GTT_PAGE_SIZE_4K)) {
> +                               pr_err("%s:%d page_sizes.gtt=%u, expected %llu\n",
> +                                               __func__, __LINE__,
>                                        vma->page_sizes.gtt, I915_GTT_PAGE_SIZE_4K);
>                                 err = -EINVAL;
>                         }
> @@ -1471,7 +1475,7 @@ static int igt_ppgtt_pin_update(void *arg)
>                 if (err)
>                         goto out_unpin;
>
> -               if (vma->page_sizes.gtt != page_size) {
> +               if (!(vma->page_sizes.gtt & -page_size)) {
>                         dma_addr_t addr = i915_gem_object_get_dma_address(obj, 0);
>
>                         /*
> @@ -1481,7 +1485,8 @@ static int igt_ppgtt_pin_update(void *arg)
>                          * address.
>                          */
>                         if (IS_ALIGNED(addr, page_size)) {
> -                               pr_err("page_sizes.gtt=%u, expected=%u\n",
> +                               pr_err("%s:%d page_sizes.gtt=%u, expected=%u\n",
> +                                               __func__, __LINE__,
>                                        vma->page_sizes.gtt, page_size);
>                                 err = -EINVAL;
>                         } else {
> --
> 2.19.1
>
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