On 9/16/21 11:58 AM, Matthew Auld wrote:
On 16/09/2021 10:03, Thomas Hellström wrote:
On Thu, 2021-09-16 at 08:55 +0200, Christian König wrote:
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)) {
I saw there was previously a thought about testing for ttm_bo_type_sg here. Was that a dead end?
I guess the issue was userptr, which is also EXTERNAL and needs to be rejected here, but underneath it's not type_sg.
OK, I thought userptr was using type_sg. I wonder what it's for if that's not the case...
Just having an explicit MAPPABLE flag or similar seemed the more flexible approach? Happy to try out other ideas.
I'm fine with a flag as well.
/Thomas