Re: [Intel-gfx] [PATCH v10 03/11] drm/ttm: Add a generic TTM memcpy move for page-based iomem

From: Dave Airlie <airlied@gmail.com>
To: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>,
	"Ben Skeggs" <skeggsb@gmail.com>
Cc: "Intel Graphics Development" <intel-gfx@lists.freedesktop.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	"Christian König" <christian.koenig@amd.com>
Subject: Re: [Intel-gfx] [PATCH v10 03/11] drm/ttm: Add a generic TTM memcpy move for page-based iomem
Date: Mon, 30 Aug 2021 11:54:07 +1000	[thread overview]
Message-ID: <CAPM=9twjYTME6CPuNmn3S7A_ACUNhMOAY1QcpoOqAZ5RHM6JzA@mail.gmail.com> (raw)
In-Reply-To: <20210602083818.241793-4-thomas.hellstrom@linux.intel.com>

I've just been talking with Ben about nouveau having some issues since
this path,

ttm_resource can be subclassed by drivers, and the code below that
copies ttm_resources around pretty much seems to destroy that.

> +       struct ttm_resource *src_mem = &bo->mem;
> +       struct ttm_resource_manager *src_man =
> +               ttm_manager_type(bdev, src_mem->mem_type);
> +       struct ttm_resource src_copy = *src_mem;

This here ^^

> +       union {
> +               struct ttm_kmap_iter_tt tt;
> +               struct ttm_kmap_iter_linear_io io;
> +       } _dst_iter, _src_iter;
> +       struct ttm_kmap_iter *dst_iter, *src_iter;
> +       int ret = 0;
>
> -       /*
> -        * TTM might be null for moves within the same region.
> -        */
> -       if (ttm) {
> +       if (ttm && ((ttm->page_flags & TTM_PAGE_FLAG_SWAPPED) ||
> +                   dst_man->use_tt)) {
>                 ret = ttm_tt_populate(bdev, ttm, ctx);
>                 if (ret)
> -                       goto out1;
> +                       return ret;
>         }
>
> -       for (i = 0; i < new_mem->num_pages; ++i) {
> -               if (old_iomap == NULL) {
> -                       pgprot_t prot = ttm_io_prot(bo, old_mem, PAGE_KERNEL);
> -                       ret = ttm_copy_ttm_io_page(ttm, new_iomap, i,
> -                                                  prot);
> -               } else if (new_iomap == NULL) {
> -                       pgprot_t prot = ttm_io_prot(bo, new_mem, PAGE_KERNEL);
> -                       ret = ttm_copy_io_ttm_page(ttm, old_iomap, i,
> -                                                  prot);
> -               } else {
> -                       ret = ttm_copy_io_page(new_iomap, old_iomap, i);
> -               }
> -               if (ret)
> -                       goto out1;
> +       dst_iter = ttm_kmap_iter_linear_io_init(&_dst_iter.io, bdev, dst_mem);
> +       if (PTR_ERR(dst_iter) == -EINVAL && dst_man->use_tt)
> +               dst_iter = ttm_kmap_iter_tt_init(&_dst_iter.tt, bo->ttm);
> +       if (IS_ERR(dst_iter))
> +               return PTR_ERR(dst_iter);
> +
> +       src_iter = ttm_kmap_iter_linear_io_init(&_src_iter.io, bdev, src_mem);
> +       if (PTR_ERR(src_iter) == -EINVAL && src_man->use_tt)
> +               src_iter = ttm_kmap_iter_tt_init(&_src_iter.tt, bo->ttm);
> +       if (IS_ERR(src_iter)) {
> +               ret = PTR_ERR(src_iter);
> +               goto out_src_iter;
>         }
> -       mb();
> -out2:
> -       old_copy = *old_mem;
>
> -       ttm_bo_assign_mem(bo, new_mem);
> -
> -       if (!man->use_tt)
> -               ttm_bo_tt_destroy(bo);
> +       ttm_move_memcpy(bo, dst_mem->num_pages, dst_iter, src_iter);
> +       src_copy = *src_mem;
> +       ttm_bo_move_sync_cleanup(bo, dst_mem);
>
> -out1:
> -       ttm_resource_iounmap(bdev, old_mem, new_iomap);
> -out:
> -       ttm_resource_iounmap(bdev, &old_copy, old_iomap);
> +       if (!src_iter->ops->maps_tt)
> +               ttm_kmap_iter_linear_io_fini(&_src_iter.io, bdev, &src_copy);

passes a copy into linear_io_fini which calls the driver io_mem_free
without the subclass data.

Dave.