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Tue, 02 Jun 2026 15:18:50 -0700 (PDT) From: Askar Safin To: kas@kernel.org Cc: Liam.Howlett@oracle.com, aarcange@redhat.com, akpm@linux-foundation.org, corbet@lwn.net, david@kernel.org, jthoughton@google.com, kernel-team@meta.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, pbonzini@redhat.com, peterx@redhat.com, rppt@kernel.org, seanjc@google.com, sj@kernel.org, skhan@linuxfoundation.org, surenb@google.com, usama.arif@linux.dev, vbabka@kernel.org, ziy@nvidia.com Subject: Re: [PATCH v6 14/15] selftests/mm: add userfaultfd RWP tests Date: Wed, 3 Jun 2026 01:18:31 +0300 Message-ID: <20260602221831.77366-1-safinaskar@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260529172716.357179-15-kas@kernel.org> References: <20260529172716.357179-15-kas@kernel.org> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit "Kiryl Shutsemau (Meta)" : > +/* > + * Test that GUP resolves through protnone PTEs (async mode). > + * vmsplice() into a pipe pins user pages via get_user_pages_fast() -- > + * unlike write(), which goes through copy_from_user() and ordinary > + * hardware page faults -- so it exercises gup_can_follow_protnone() on > + * the RW-protected PTE. In async mode the kernel auto-restores > + * permissions and GUP returns the page. > + */ Note that I recently submitted a patch, which makes vmsplice equivalent to preadv2/pwritev2, and it was accepted to next. For now it is just an experiment, it is possible it will be reverted. https://lore.kernel.org/all/20260601-aufweichen-dissens-ausrechnen-0d9b84728113@brauner/ -- Askar Safin