Re: [PATCH v3 06/12] drm/ttm: add TTM_PAGE_FLAG_EXTERNAL_MAPPABLE

Am 15.09.21 um 20:59 schrieb Matthew Auld:

In commit:

commit 667a50db0477d47fdff01c666f5ee1ce26b5264c Author: Thomas Hellstrom thellstrom@vmware.com Date: Fri Jan 3 11:17:18 2014 +0100

 drm/ttm: Refuse to fault (prime-) imported pages

we introduced the restriction that imported pages should not be directly mappable through TTM(this also extends to userptr). In the next patch we want to introduce a shmem_tt backend, which should follow all the existing rules with TTM_PAGE_FLAG_EXTERNAL, since it will need to handle swapping itself, but with the above mapping restriction lifted.

Signed-off-by: Matthew Auld matthew.auld@intel.com Cc: Thomas Hellström thomas.hellstrom@linux.intel.com Cc: Christian König christian.koenig@amd.com

---

drivers/gpu/drm/ttm/ttm_bo_vm.c | 6 ++++-- include/drm/ttm/ttm_tt.h | 7 +++++++ 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c index 708390588c7c..fd6e18f12f50 100644 --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c @@ -163,8 +163,10 @@ vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo, * (if at all) by redirecting mmap to the exporter. */ if (bo->ttm && (bo->ttm->page_flags & TTM_PAGE_FLAG_EXTERNAL)) {

• dma_resv_unlock(bo->base.resv);
  

• return VM_FAULT_SIGBUS;
  

• if (!(bo->ttm->page_flags & TTM_PAGE_FLAG_EXTERNAL_MAPPABLE)) {
  

• 	dma_resv_unlock(bo->base.resv);
  

• 	return VM_FAULT_SIGBUS;
  

• }
  

  }

  return 0;

diff --git a/include/drm/ttm/ttm_tt.h b/include/drm/ttm/ttm_tt.h index 7f54a83c95ef..800c9edb3e10 100644 --- a/include/drm/ttm/ttm_tt.h +++ b/include/drm/ttm/ttm_tt.h @@ -66,11 +66,18 @@ struct ttm_tt { * Note that enum ttm_bo_type.ttm_bo_type_sg objects will always enable * this flag. *

• * TTM_PAGE_FLAG_EXTERNAL_MAPPABLE: Same behaviour as
  

• * TTM_PAGE_FLAG_EXTERNAL, but with the reduced restriction that it is
  

• * still valid to use TTM to map the pages directly. This is useful when
  

• * implementing a ttm_tt backend which still allocates driver owned
  

• * pages underneath(say with shmem).
  

• *
  

  • TTM_PAGE_FLAG_PRIV_POPULATED: TTM internal only. DO NOT USE.
  */ #define TTM_PAGE_FLAG_SWAPPED (1 << 0) #define TTM_PAGE_FLAG_ZERO_ALLOC (1 << 1) #define TTM_PAGE_FLAG_EXTERNAL (1 << 2)

+#define TTM_PAGE_FLAG_EXTERNAL_MAPPABLE (1 << 3 | TTM_PAGE_FLAG_EXTERNAL)

That's really bad practice because an "if (!(flags & TTM_PAGE_FLAG_EXTERNAL_MAPPABLE))" has a different semantics as an "if (flags & TTM_PAGE_FLAG_EXTERNAL_MAPPABLE)".

Rather add a TTM_PAGE_FLAG_UNMAPPABLE and make sure that it is set as appropriated.

Regards, Christian.

#define TTM_PAGE_FLAG_PRIV_POPULATED (1 << 31) uint32_t page_flags;