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Wed, 21 Oct 2026 09:50:00 +0000 X-Mizu-Trace-ID: 83e3e21a2d7caf67 X-Migadu-Flow: FLOW_OUT Message-ID: <2329ee64-f9be-4826-a496-65344e9a9c18@linux.dev> Date: Wed, 21 Oct 2026 17:49:51 +0800 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/ksm: keep soft-dirty and uffd-wp when merging a page To: Kiryl Shutsemau , "David Hildenbrand (Arm)" Cc: samarth.colleges@gmail.com, akpm@linux-foundation.org, xu.xin@linux.dev, chengming.zhou@linux.dev, peterx@redhat.com, rppt@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20261020055518.36087-1-lance.yang@linux.dev> <3da45e6d-2b46-4fff-9ff3-241f70d68296@kernel.org> <68f17ee7-d272-4475-8a59-645442e2c210@kernel.org> Content-Language: en-US From: Lance Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 9D31F1C0004 X-Stat-Signature: 66iu4rawpqd96s8uz5e4ket1osg8wn9k X-Rspamd-Server: rspam01 X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1792576201-117157 X-HE-Meta: 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 x9iHBwUt SNwwpc5ZPaXP+Rd+8yZVO5dmRysd7+YrZqySF2mP8M/W27lYO1oEJWh4aZiWCWM5fElQZHgTolMnroh0m6dV6ueiEPRVwlX2KtfVMipROP5/ePDXThJDtS5Q25dWrK9T4knmLOQy4H35iJPIaH6E4JKOBK0SKF3U5QIceDNxolz2ihySgY3odUPEK8Nq2b4zWgR5NCyzOIx2Wr5xUY0gt3RqzB3NyBGUI/j56N18u20M9Dnkp/5vH5jI6naCpbLlRdhjOJQcqe0IlTZUYSEAElzWCLKdKzq6ghnkYGNA5LRim67MJ57v0zyW2i6A3+D+Kv3kcK2ICsfumGoxuJO+dlp5ywVh5fERzQX7o2Mt4Pa46zyv0F9uh6OXYKX2wACgo3mHj Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 2026/10/21 16:55, Kiryl Shutsemau wrote: > On Wed, Oct 21, 2026 at 10:21:53AM +0200, David Hildenbrand (Arm) wrote: >>> +1. Did it ever actually work there :) Why not just skip them and >>> call it a day :D >> >> I think QEMU just always sets MADV_MERGABLE and later activates uffd. So that >> needs some care to not disable them. So let's rather try to get it fixed properly. >> >> Can you send out proper patches? Thanks! Thanks David! Will take it over next week and get proper patches out :) > > +1. > > Lance's direction is right. Unsharing is not an access: do_wp_page() > already skips the uffd-wp fault on FAULT_FLAG_UNSHARE, and RWP should do > the same. Thanks Kiryl! Will take a close look at that :) Cheers, Lance