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Howlett" , Yun Zhou , Suren Baghdasaryan , Alex Sierra , Matthew Wilcox , Pasha Tatashin , Mike Rapoport , Nadav Amit , Axel Rasmussen , "Gustavo A . R . Silva" , Dan Williams , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Greg KH , kernel@collabora.com Subject: Re: [PATCH v7 1/4] userfaultfd: Add UFFD WP Async support Content-Language: en-US To: Peter Xu References: <20230109064519.3555250-1-usama.anjum@collabora.com> <20230109064519.3555250-2-usama.anjum@collabora.com> <0bed5911-48b9-0cc2-dfcf-d3bc3b0e8388@collabora.com> <328f54c1-171f-22a1-10c9-8b7a25bd8027@collabora.com> From: Muhammad Usama Anjum In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 82C2940006 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: yzbk83yw38e4ffd5bwjqeg5a4k6c8p5k X-HE-Tag: 1674649147-395610 X-HE-Meta: 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 0ob6c6EW r1oRKK+SOjy5rtHFwMerXqOZyBqV7usi7gfB+LHByN0hcvy6H1RLgWDFTCfqqEbKIqAmMJP24RoA7HhtI+JBb8PuGyT8gj9n3ROtwFCzwpCxux6NRMLtU5zHzs45Xl+5KJSEd1PozrMT5lRuEfl3sYrX46uTF/jO9fFbs/pqRxXYhSCBQ/zOPRuy/f+v98LhzhjSG83PuR3w02V8gWQacyOpr7e56Tt99hOZVr7P06fgg0Q+zhLY8j8K485m01EQHWhzNbpgCd1BfGvH/tyxWEq02HQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 1/24/23 10:26 PM, Peter Xu wrote: > On Mon, Jan 23, 2023 at 03:11:20PM +0500, Muhammad Usama Anjum wrote: >>> One thing worth mention is, I think for async wp it doesn't need to be >>> restricted by UFFD_USER_MODE_ONLY, because comparing to the sync messages >>> it has no risk of being utilized for malicious purposes. >> I think with updated handling path updated in do_wp_page() and >> wp_huge_pmd() in version, UFFD_USER_MODE_ONLY will not affect us. > > This is more or less a comment for the design, the new code should work (by > bypassing handle_userfaultfd(), where this bit was checked). > > We'll need an man page update if this feature will be merged [1], and if so > it'll need to be updated for the UFFD_USER_MODE_ONLY section regarding to > async uffd-wp support too. I think that can also be worked out after the > series being accepted first, so just a heads up. > > [1] https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git Thank you for explaining it. Definitely, we'll update the man pages after the change has been merged. I've added it to my notes.> -- BR, Muhammad Usama Anjum