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Wed, 5 Nov 2025 18:25:10 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 9YknO4aWC2lcOgAAD6G6ig (envelope-from ); Wed, 05 Nov 2025 18:25:10 +0000 Message-ID: <2b32ada6-01ff-4ab7-8094-8c0078ca585b@suse.cz> Date: Wed, 5 Nov 2025 19:25:10 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/16] mm: correctly handle UFFD PTE markers Content-Language: en-US To: Lorenzo Stoakes , Andrew Morton Cc: Christian Borntraeger , Janosch Frank , Claudio Imbrenda , David Hildenbrand , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Sven Schnelle , Peter Xu , Alexander Viro , Christian Brauner , Jan Kara , Arnd Bergmann , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Muchun Song , Oscar Salvador , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Axel Rasmussen , Yuanchu Xie , Wei Xu , Kemeng Shi , Kairui Song , Nhat Pham , Baoquan He , Chris Li , SeongJae Park , Matthew Wilcox , Jason Gunthorpe , Leon Romanovsky , Xu Xin , Chengming Zhou , Jann Horn , Miaohe Lin , Naoya Horiguchi , Pedro Falcato , Pasha Tatashin , Rik van Riel , Harry Yoo , Hugh Dickins , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, damon@lists.linux.dev References: <6918f70e17e23341d2425328bb991e2e094f7a7e.1762171281.git.lorenzo.stoakes@oracle.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <6918f70e17e23341d2425328bb991e2e094f7a7e.1762171281.git.lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: BF7322000D X-Rspamd-Server: rspam07 X-Stat-Signature: 8k54fgt51ktxy3d3ogtj8gefsgxhqaxd X-Rspam-User: X-HE-Tag: 1762367113-373993 X-HE-Meta: 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 ZtxTCEQY uDe1FQGFYzWxBdItc4KtQq/QX1r9If8V6Sbq8QoZI+ucCm1raBKo9F/qGXNXxMVSR+i3RohNBZtbvI7saf1dtFLhhJzG063wx/Q9nJdmf96E9K0yINdJnnf8d+tk01fUY/izfYYKk/jw5t2IWS4FhDS57537+X29LgSAXm8nUIIUTTvWpjQmQwEmo2QPzSOBJtr0Gk6SQr5UWcl0W1dNH31t+NpzVR8VKAPaweL+3NWt5BExDX9aRmvo7faumwQDlpfpeuVqmRPld5yrb51idzVdxtH21QWx7cgYmqT+HsVf1yd2JyITGxKjUWNy7hJQDnh+E8JXF5oIj9lEE5bmRgqtBIjayb7FrL0bIJAakLJG+awpGYzJRfUloubk8D+OuuQM1 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: List-Subscribe: List-Unsubscribe: On 11/3/25 13:31, Lorenzo Stoakes wrote: > PTE markers were previously only concerned with UFFD-specific logic - that > is, PTE entries with the UFFD WP marker set or those marked via > UFFDIO_POISON. > > However since the introduction of guard markers in commit > 7c53dfbdb024 ("mm: add PTE_MARKER_GUARD PTE marker"), this has no longer > been the case. > > Issues have been avoided as guard regions are not permitted in conjunction > with UFFD, but it still leaves very confusing logic in place, most notably > the misleading and poorly named pte_none_mostly() and > huge_pte_none_mostly(). > > This predicate returns true for PTE entries that ought to be treated as > none, but only in certain circumstances, and on the assumption we are > dealing with H/W poison markers or UFFD WP markers. > > This patch removes these functions and makes each invocation of these > functions instead explicitly check what it needs to check. > > As part of this effort it introduces is_uffd_pte_marker() to explicitly > determine if a marker in fact is used as part of UFFD or not. > > In the HMM logic we note that the only time we would need to check for a > fault is in the case of a UFFD WP marker, otherwise we simply encounter a > fault error (VM_FAULT_HWPOISON for H/W poisoned marker, VM_FAULT_SIGSEGV > for a guard marker), so only check for the UFFD WP case. > > While we're here we also refactor code to make it easier to understand. > > Signed-off-by: Lorenzo Stoakes Nice cleanup! Reviewed-by: Vlastimil Babka