[PATCH] drm/amdgpu: break COW for user ptr during fork()

[Lang Yu]

This is useful to prevent copy-on-write semantics
from changing the physical location of a page if
the parent writes to it after a fork().

Signed-off-by: Lang Yu <Lang.Yu at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 1 +
 drivers/gpu/drm/amd/amdkfd/kfd_svm.c    | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 75c9fd2c6c2a..2ee0af3c41b1 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -693,6 +693,7 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages,
 	}
 
 	readonly = amdgpu_ttm_tt_is_readonly(ttm);
+	vm_flags_set(vma, VM_DONTCOPY);
 	r = amdgpu_hmm_range_get_pages(&bo->notifier, start, ttm->num_pages,
 				       readonly, NULL, pages, range);
 out_unlock:
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 6aa032731ddc..607a8f68f26f 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -1674,6 +1674,7 @@ static int svm_range_validate_and_map(struct mm_struct *mm,
 			next = min(vma->vm_end, end);
 			npages = (next - addr) >> PAGE_SHIFT;
 			WRITE_ONCE(p->svms.faulting_task, current);
+			vm_flags_set(vma, VM_DONTCOPY);
 			r = amdgpu_hmm_range_get_pages(&prange->notifier, addr, npages,
 						       readonly, owner, NULL,
 						       &hmm_range);
-- 
2.25.1