[Intel-gfx] [PATCH 02/39] drm/i915/gem: Use set_pte_at() for assigning the vmapped PTE

[Matthew Auld]

On Wed, 26 Aug 2020 at 14:28, Chris Wilson <chris at chris-wilson.co.uk> wrote:
>
> Use set_pte_at() to assign the PTE pointer returned by alloc_vm_area(),
> rather than a direct assignment.

and crucially add the missing sync stuff for the mapping?

>
> Fixes: 6056e50033d9 ("drm/i915/gem: Support discontiguous lmem object maps")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Matthew Auld <matthew.auld at intel.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_pages.c | 33 +++++++++++++++++++----
>  1 file changed, 28 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> index 51b63e05dbe4..0c3d0d6429ae 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
> @@ -241,6 +241,17 @@ static inline pte_t iomap_pte(resource_size_t base,
>         return pte_mkspecial(pfn_pte((base + offset) >> PAGE_SHIFT, prot));
>  }
>
> +static void sync_vm_area(struct vm_struct *area)
> +{
> +       unsigned long start = (unsigned long)area->addr;
> +       unsigned long end = start + area->size;
> +
> +       if (ARCH_PAGE_TABLE_SYNC_MASK & PGTBL_PTE_MODIFIED)
> +               arch_sync_kernel_mappings(start, end); /* expected DCE */

What is DCE again?

> +
> +       flush_cache_vmap(start, end);
> +}
> +
>  /* The 'mapping' part of i915_gem_object_pin_map() below */
>  static void *i915_gem_object_map(struct drm_i915_gem_object *obj,
>                                  enum i915_map_type type)
> @@ -308,24 +319,36 @@ static void *i915_gem_object_map(struct drm_i915_gem_object *obj,
>         }
>
>         if (i915_gem_object_has_struct_page(obj)) {
> +               unsigned long addr = (unsigned long)area->addr;
>                 struct sgt_iter iter;
>                 struct page *page;
>                 pte_t **ptes = mem;
>
> -               for_each_sgt_page(page, iter, sgt)
> -                       **ptes++ = mk_pte(page, pgprot);
> +               for_each_sgt_page(page, iter, sgt) {
> +                       set_pte_at(&init_mm, addr, *ptes, mk_pte(page, pgprot));

init_mm needs to be exported?

> +                       addr += PAGE_SIZE;
> +                       ptes++;
> +               }
> +               GEM_BUG_ON(addr != (unsigned long)area->addr + obj->base.size);
>         } else {
> +               unsigned long addr = (unsigned long)area->addr;
>                 resource_size_t iomap;
>                 struct sgt_iter iter;
>                 pte_t **ptes = mem;
> -               dma_addr_t addr;
> +               dma_addr_t offset;
>
>                 iomap = obj->mm.region->iomap.base;
>                 iomap -= obj->mm.region->region.start;
>
> -               for_each_sgt_daddr(addr, iter, sgt)
> -                       **ptes++ = iomap_pte(iomap, addr, pgprot);
> +               for_each_sgt_daddr(offset, iter, sgt) {
> +                       set_pte_at(&init_mm, addr, *ptes,
> +                                  iomap_pte(iomap, offset, pgprot));
> +                       addr += PAGE_SIZE;
> +                       ptes++;
> +               }
> +               GEM_BUG_ON(addr != (unsigned long)area->addr + obj->base.size);
>         }
> +       sync_vm_area(area);
>
>         if (mem != stack)
>                 kvfree(mem);
> --
> 2.20.1
>
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