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b=tfDNQUaxol6LRd60RlzKMPBwZeRswtt0gijLKRle/y1Gh2I8LCYZPLlSGuyVRuaXo 51KnhnRizLNklEFx071MubuAC2yWZkUVVvh54WEZaNBLoexRQsc2eG26lodtQXLGlM oI/QKSm+xuFjQlMaAei1lExj53BlnuTkSXYqRZCwHwg9R/WwTh2j9VA8fpTX4uLXV6 jPdw41sY/fP161N7mgDB0lonw74jjjnDVcu//OG7HFE50IXE3C68Lf2V+z7mwJ78Uy npy24JfcTGg6xdNBU+M2rp91Q0ZhlJLwe+IiGGd2raRV+o+sh90pV6lVkRhLAe5a0K A9yNbLsJuqUOA== Message-ID: <4e52f70d-e0c3-471f-8073-68c0e9bc94ca@kernel.org> Date: Mon, 16 Mar 2026 17:48:24 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv7 09/18] mm/hugetlb: Defer vmemmap population for bootmem hugepages To: "Kiryl Shutsemau (Meta)" , Andrew Morton , Muchun Song , Matthew Wilcox , Usama Arif , Frank van der Linden Cc: Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Zi Yan , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , Huacai Chen , WANG Xuerui , Palmer Dabbelt , Paul Walmsley , Albert Ou , Alexandre Ghiti , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org References: <20260227194302.274384-1-kas@kernel.org> <20260227194302.274384-10-kas@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 0B27820008 X-Stat-Signature: w4fwpss6icb9wsfsjfo51ys6kgrs4fpf X-Rspam-User: X-HE-Tag: 1773679713-343118 X-HE-Meta: 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 41I1uxbo PQFo582nuWGoOLGCsTRSOUwk+/u4oNxpkzGFB0sw49PAAsi9R0qpbaSRgKFruIy27rCsnpuqcJIG3WMTpYBasfUaAIlhkBFFojfZ0MbDCoDqg0ty1Hyi3+CmZQkwCyJIffYWlBGfjzw0Eyaq1do3PFhOEGmyXgOFCDYZys07heqMaRmLsY38bEGdVW7Y4ZeK7gd/uQDDtUR6cXCHFMrobdNPWgOrC39fprVprL4Wv0OFa2C3b7rabRGaVCyWxEDpfetxJUff8ir24z6fqRyrRhbqvg71inTQA1D6K Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/27/26 20:42, Kiryl Shutsemau (Meta) wrote: > Currently, the vmemmap for bootmem-allocated gigantic pages is populated > early in hugetlb_vmemmap_init_early(). However, the zone information is > only available after zones are initialized. If it is later discovered > that a page spans multiple zones, the HVO mapping must be undone and > replaced with a normal mapping using vmemmap_undo_hvo(). > > Defer the actual vmemmap population to hugetlb_vmemmap_init_late(). At > this stage, zones are already initialized, so it can be checked if the > page is valid for HVO before deciding how to populate the vmemmap. > > This allows us to remove vmemmap_undo_hvo() and the complex logic > required to rollback HVO mappings. > > In hugetlb_vmemmap_init_late(), if HVO population fails or if the zones > are invalid, fall back to a normal vmemmap population. > > Postponing population until hugetlb_vmemmap_init_late() also makes zone > information available from within vmemmap_populate_hvo(). So we'll keep marking the sections as SECTION_IS_VMEMMAP_PREINIT such that sparse_init_nid() will still properly skip it and leave population to hugetlb_vmemmap_init_late(). Should we clear SECTION_IS_VMEMMAP_PREINIT in case we run into the hugetlb_bootmem_page_zones_valid() scenario? I suspect we don't care about SECTION_IS_VMEMMAP_PREINIT after boot and can just leave the flag set. (maybe we wan to add a comment in the code? above the vmemmap_populate() ?) Nothing else jumped at me Acked-by: David Hildenbrand (Arm) -- Cheers, David