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[83.60.147.6]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-498362eb158sm11708192f8f.36.2026.11.11.08.54.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Nov 2026 08:54:21 -0800 (PST) Message-ID: <6a2c3f50-bce4-4214-8621-e0daa0637e91@gmail.com> Date: Wed, 11 Nov 2026 17:54:19 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/4] mm/huge_memory: don't warn when a page table blocks a huge pfn insert To: Eliav Farber , Andrew Morton Cc: David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , x86@kernel.org, William Kucharski , Vishal Moola , Alex Williamson , Peter Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20261111140655.34281-1-farbere@amazon.com> <20261111140655.34281-4-farbere@amazon.com> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: <20261111140655.34281-4-farbere@amazon.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: bofxcb4c5ghi551segc7hqw5byfaw9j1 X-Rspamd-Queue-Id: CEF2CC0002 X-Rspam-User: X-Rspamd-Server: rspam08 X-Spam-Status: No, score=-9.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_PASS,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794416063-173188 X-HE-Meta: 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 7Yuoqb3w 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 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 11/11/26 3:06 PM, Eliav Farber wrote: > insert_pmd() and insert_pud() treat a non-empty entry at their own level > as a leaf and compare its PFN against the one being inserted. A page > table installed by a concurrent order-0 fault also makes the entry > non-empty, and pmd_pfn()/pud_pfn() then report the PFN of that table, > which never matches. insert_pmd() warns unless the entry is the huge > zero PMD, and insert_pud() warns on any mismatch. > > A VM_PFNMAP mapping with both ->fault and ->huge_fault can produce the > mixed orders: an order-0 fault installs a page table over an address > while a concurrent huge fault on the same address reaches insert_pmd(). > Changing an mm's THP policy while another thread faults the same PMD, > for example with prctl(PR_SET_THP_DISABLE), is enough to do it. > > Compare the PFN only for a leaf entry. A page table is not an error, so > take the existing out_unlock path, which returns VM_FAULT_NOPAGE and > lets the access refault onto the smaller entry. > > Fixes: f9e54c3a2f5b ("vfio/pci: implement huge_fault support") > Signed-off-by: Eliav Farber LGTM: Reviewed-by: Jose A. Perez de Azpillaga -- cheers, jose a. p-a