<html><head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> </head> <body> <div class="moz-cite-prefix">On 2024-02-21 21:01, Lang Yu wrote: </div> <blockquote type="cite" cite="mid:20240222020124.1302449-1-Lang.Yu@amd.com"> <pre class="moz-quote-pre" wrap="">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 <a class="moz-txt-link-rfc2396E" href="mailto:Lang.Yu@amd.com"><Lang.Yu@amd.com></a> --- 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);</pre> </blockquote> This will break user mode because the forked child process cannot access this vma/userptr. This can be set by application if needed, using madvise(...MADV_DONTFORK) to avoid COW after fork. Regards, Philip <blockquote type="cite" cite="mid:20240222020124.1302449-1-Lang.Yu@amd.com"> <pre class="moz-quote-pre" wrap=""> 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); </pre> </blockquote> </body> </html>