Messages in this thread | | | Subject | Re: [PATCH] drm/ttm: don't set page->mapping | From | Christian König <> | Date | Fri, 20 Nov 2020 11:08:31 +0100 |
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Am 20.11.20 um 11:05 schrieb Daniel Vetter: > On Fri, Nov 20, 2020 at 11:04 AM Christian König > <christian.koenig@amd.com> wrote: >> Am 20.11.20 um 10:54 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. >>> >>> 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> >> This is still a NAK as long as we can't come up with a better way to >> track TTMs page allocations. >> >> Additional to that page_mapping() is used quite extensively in the mm >> code and I'm not sure if that isn't needed for other stuff as well. > Apologies, I'm honestly not quite sure how this lone patch here ended > up in this submission. I didn't want to send it out.
No problem.
But looking a bit deeper into the mm code that other drm drivers don't set this correctly and still use unmap_mapping_range() sounds like quite a bug to me.
Going to track down what exactly that is used for.
Christian.
> -Daniel > >> Regards, >> Christian. >> >>> --- >>> 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 da9eeffe0c6d..5b2eb6d58bb7 100644 >>> --- a/drivers/gpu/drm/ttm/ttm_tt.c >>> +++ b/drivers/gpu/drm/ttm/ttm_tt.c >>> @@ -284,17 +284,6 @@ 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) >>> { >>> @@ -313,7 +302,6 @@ 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); >
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