On Wed, May 31, 2017 at 07:52:01PM +0100, Matthew Auld wrote:
> We can't mix 64K and 4K pte's in the same page-table, so for now we
> align 64K objects to 2M to avoid any potential mixing. This is
> potentially wasteful but in reality shouldn't be too bad since this only
> applies to the virtual address space of a 48b PPGTT.
>
> Suggested-by: Chris Wilson <[email protected]>
> Signed-off-by: Matthew Auld <[email protected]>
> Cc: Joonas Lahtinen <[email protected]>
> ---
> drivers/gpu/drm/i915/i915_vma.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index c355ccb01872..af950d92fa13 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -479,6 +479,15 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64
> alignment, u64 flags)
> goto err_unpin;
> }
>
> + /* A current limitation in our implementation is that 64K
> + * objects must be aligned to 2M, and given that we can't
> + * enforce this for soft pinning, we need to fallback to normal
> + * pages if don't meet this restriction.
> + */
> + if (obj->mm.page_sizes.sg == I915_GTT_PAGE_SIZE_64K &&
page_sizes.sg > I915_GTT_PAGE_SIZE_4K.
> + !IS_ALIGNED(offset | size, I915_GTT_PAGE_SIZE_2M))
Abusing the semantics of PAGE_SIZE_2M. It just happens to be the value
you want, but it doesn't mean what you say.
> + obj->mm.page_sizes.sg = I915_GTT_PAGE_SIZE;
> +
> ret = i915_gem_gtt_reserve(vma->vm, &vma->node,
> size, offset, obj->cache_level,
> flags);
> @@ -493,6 +502,15 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64
> alignment, u64 flags)
> if (!is_power_of_2(page_alignment))
> page_alignment = BIT(fls64(page_alignment)-1);
>
> + /* We can't mix 64K and 4K pte's in the same page-table
> (2M
> + * block), and so to avoid the ugliness and complexity
> of
> + * coloring we opt for just aligning 64K objects to 2M.
> + */
> + if (obj->mm.page_sizes.sg == I915_GTT_PAGE_SIZE_64K) {
page_sizes.sg & SIZE_64K or page_sizes.sg > SIZE_4K
Also refer to earlier discussion that this should be vma->page_sizes
here not obj.
> + page_alignment = I915_GTT_PAGE_SIZE_2M;
> + size = roundup(size, page_alignment);
round_up.
> + }
> +
> alignment = max_t(typeof(alignment), alignment,
> page_alignment);
> }
> --
> 2.9.4
>
> _______________________________________________
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> [email protected]
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Chris Wilson, Intel Open Source Technology Centre
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