When an application having open file access to a node forks, its shared mappings also get reflected in the address space of child process even though it cannot access them with the object permissions applied. With the existing permission checks on the gem objects, it might be reasonable to also create the VMAs with VM_DONTCOPY flag so a user space application doesn't need to explicitly call the madvise(addr, len, MADV_DONTFORK) system call to prevent the pages in the mapped range to appear in the address space of the child process. It also prevents the memory leaks due to additional reference counts on the mapped BOs in the child process that prevented freeing the memory in the parent for which we had worked around earlier in the user space inside the thunk library.
Additionally, we faced this issue when using CRIU to checkpoint restore an application that had such inherited mappings in the child which confuse CRIU when it mmaps on restore. Having this flag set for the render node VMAs helps. VMAs mapped via KFD already take care of this so this is needed only for the render nodes.
To limit the impact of the change to user space consumers such as OpenGL etc, limit it to KFD BOs only.
Cc: Felix Kuehling Felix.Kuehling@amd.com
Signed-off-by: David Yat Sin david.yatsin@amd.com Signed-off-by: Rajneesh Bhardwaj rajneesh.bhardwaj@amd.com ---
Changes in v2: * Addressed Christian's concerns for user space impact * Further reduced the scope to KFD BOs only
drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c index a224b5295edd..64a7931eda8c 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c @@ -263,6 +263,9 @@ static int amdgpu_gem_object_mmap(struct drm_gem_object *obj, struct vm_area_str !(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))) vma->vm_flags &= ~VM_MAYWRITE;
+ if (bo->kfd_bo) + vma->vm_flags |= VM_DONTCOPY; + return drm_gem_ttm_mmap(obj, vma); }