[Intel-gfx] [PATCH v4 02/14] drm/ttm: stop setting page->index for the ttm_tt

Matthew Auld
2021-09-21T11:01:51Z

In commit:

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

we started setting the page->mapping and page->index to point to the
virtual address space, if the pages were faulted with TTM. Apparently
this was needed for core-mm to able to reverse lookup the virtual
address given the struct page, and potentially unmap it from the page
tables. However as pointed out by Thomas, since we are now using
PFN_MAP, instead of say PFN_MIXED, this should no longer be the case.

There was also apparently some usecase in vmwgfx which needed this for
dirty tracking, but that also doesn't appear to be the case anymore, as
pointed out by Thomas.

We still need keep the page->mapping for now, since that is still needed
for different reasons, but we try to address that in the next patch.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
---
drivers/gpu/drm/ttm/ttm_bo_vm.c | 2 --
drivers/gpu/drm/ttm/ttm_tt.c | 4 +---
2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 5b9b7fd01a69..9a2119fe4bdd 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -346,8 +346,6 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
} else if (unlikely(!page)) {
break;
}
- page->index = drm_vma_node_start(&bo->base.vma_node) +
- page_offset;
pfn = page_to_pfn(page);
}

diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
index dae52433beeb..1cc04c224988 100644
--- a/drivers/gpu/drm/ttm/ttm_tt.c
+++ b/drivers/gpu/drm/ttm/ttm_tt.c
@@ -367,10 +367,8 @@ static void ttm_tt_clear_mapping(struct ttm_tt *ttm)
if (ttm->page_flags & TTM_PAGE_FLAG_SG)
return;

- for (i = 0; i < ttm->num_pages; ++i) {
+ for (i = 0; i < ttm->num_pages; ++i)
(*page)->mapping = NULL;
- (*page++)->index = 0;
- }
}

void ttm_tt_unpopulate(struct ttm_device *bdev, struct ttm_tt *ttm)
--
2.26.3