[Intel-gfx] [PATCH 2/9] drm/i915/gtt: Use a common type for page directories

[Chris Wilson]

Quoting Mika Kuoppala (2019-06-11 18:27:24)
>  struct i915_page_table {
>         struct i915_page_dma base;
> -       atomic_t used_ptes;
> +       atomic_t used;
>  };
>  
>  struct i915_page_directory {
>         struct i915_page_dma base;
> -
> -       struct i915_page_table *page_table[I915_PDES]; /* PDEs */
> -       atomic_t used_pdes;
> -       spinlock_t lock;
> -};
> -
> -struct i915_page_directory_pointer {
> -       struct i915_page_dma base;
> -       struct i915_page_directory **page_directory;
> -       atomic_t used_pdpes;
> -       spinlock_t lock;
> -};
> -
> -struct i915_pml4 {
> -       struct i915_page_dma base;
> -       struct i915_page_directory_pointer *pdps[GEN8_PML4ES_PER_PML4];
> +       atomic_t used;
>         spinlock_t lock;
> +       void *entry[0];
>  };

And always (albeit with a single bsw discrepancy) 512. At the very least
you can alias a fixed sized variant over the top to remove the extra
pointer chasing you added.
-Chris