Re: [PATCH 1/1] drm/xen-zcopy: Add Xen zero-copy helper DRM driver

Daniel Vetter
2018-04-03T09:47:39Z

On Thu, Mar 29, 2018 at 04:19:31PM +0300, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> +static int to_refs_grant_foreign_access(struct xen_gem_object *xen_obj)
> +{
> + grant_ref_t priv_gref_head;
> + int ret, j, cur_ref, num_pages;
> + struct sg_page_iter sg_iter;
> +
> + ret = gnttab_alloc_grant_references(xen_obj->num_pages,
> + &priv_gref_head);
> + if (ret < 0) {
> + DRM_ERROR("Cannot allocate grant references\n");
> + return ret;
> + }
> +
> + j = 0;
> + num_pages = xen_obj->num_pages;
> + for_each_sg_page(xen_obj->sgt->sgl, &sg_iter, xen_obj->sgt->nents, 0) {
> + struct page *page;
> +
> + page = sg_page_iter_page(&sg_iter);

Quick drive-by: You can't assume that an sgt is struct page backed.

And you probably want to check this at import/attach time.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation