Re: [PATCH] drm/ttm: don't set page->mapping

From: "Christian König" <christian.koenig@amd.com>
To: Daniel Vetter <daniel.vetter@ffwll.ch>,
	DRI Development <dri-devel@lists.freedesktop.org>
Cc: Daniel Vetter <daniel.vetter@intel.com>,
	Thomas Hellstrom <thellstrom@vmware.com>,
	Huang Rui <ray.huang@amd.com>, Brian Paul <brianp@vmware.com>
Subject: Re: [PATCH] drm/ttm: don't set page->mapping
Date: Thu, 5 Nov 2020 08:59:59 +0100	[thread overview]
Message-ID: <859e2b9c-c202-25c6-b52f-9841fe32b082@amd.com> (raw)
In-Reply-To: <20201104165030.2005167-1-daniel.vetter@ffwll.ch>

Am 04.11.20 um 17:50 schrieb Daniel Vetter:
> Random observation while trying to review Christian's patch series to
> stop looking at struct page for dma-buf imports.
>
> This was originally added in
>
> commit 58aa6622d32af7d2c08d45085f44c54554a16ed7
> Author: Thomas Hellstrom <thellstrom@vmware.com>
> Date:   Fri Jan 3 11:47:23 2014 +0100
>
>      drm/ttm: Correctly set page mapping and -index members
>
>      Needed for some vm operations; most notably unmap_mapping_range() with
>      even_cows = 0.
>
>      Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
>      Reviewed-by: Brian Paul <brianp@vmware.com>
>
> but we do not have a single caller of unmap_mapping_range with
> even_cows == 0. And all the gem drivers don't do this, so another
> small thing we could standardize between drm and ttm drivers.
>
> Plus I don't really see a need for unamp_mapping_range where we don't
> want to indiscriminately shoot down all ptes.

NAK, we use this to determine if a pages belongs to the driver or not in 
amdgpu for example.

Mostly used for debugging, but I would really like to keep that.

Christian.

>
> Cc: Thomas Hellstrom <thellstrom@vmware.com>
> Cc: Brian Paul <brianp@vmware.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Christian Koenig <christian.koenig@amd.com>
> Cc: Huang Rui <ray.huang@amd.com>
> ---
>   drivers/gpu/drm/ttm/ttm_tt.c | 12 ------------
>   1 file changed, 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
> index 8861a74ac335..438ea43fd8c1 100644
> --- a/drivers/gpu/drm/ttm/ttm_tt.c
> +++ b/drivers/gpu/drm/ttm/ttm_tt.c
> @@ -291,17 +291,6 @@ int ttm_tt_swapout(struct ttm_bo_device *bdev, struct ttm_tt *ttm)
>   	return ret;
>   }
>   
> -static void ttm_tt_add_mapping(struct ttm_bo_device *bdev, struct ttm_tt *ttm)
> -{
> -	pgoff_t i;
> -
> -	if (ttm->page_flags & TTM_PAGE_FLAG_SG)
> -		return;
> -
> -	for (i = 0; i < ttm->num_pages; ++i)
> -		ttm->pages[i]->mapping = bdev->dev_mapping;
> -}
> -
>   int ttm_tt_populate(struct ttm_bo_device *bdev,
>   		    struct ttm_tt *ttm, struct ttm_operation_ctx *ctx)
>   {
> @@ -320,7 +309,6 @@ int ttm_tt_populate(struct ttm_bo_device *bdev,
>   	if (ret)
>   		return ret;
>   
> -	ttm_tt_add_mapping(bdev, ttm);
>   	ttm->page_flags |= TTM_PAGE_FLAG_PRIV_POPULATED;
>   	if (unlikely(ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)) {
>   		ret = ttm_tt_swapin(ttm);

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel