From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 35A0347276D for ; Fri, 27 Feb 2026 20:09:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772222995; cv=none; b=lHcEIw7aMUGW15CcHJoJqc4tjwcrz3IqHLG+He3WIO0wKD1/KjtNzo5s9yOfNBF5CRB6Bwk7UNtdLWJNZFErscW4cq+RClndo7H7HsXPqcXPfV6DZUVR2JylMZKtge5RvCj+5/Q7gvNQbWoctj6rXspC6b5CqanQknma7X/7/M4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772222995; c=relaxed/simple; bh=5N9ATerv0OaDW11j0jD0bDVQgayVJDS/nufTwYczaIo=; h=Date:To:From:Subject:Message-Id; b=NFysHvbE8SO7DgX1mH5b8HvvuabtzjDySJN2GBdfIv4hfLrAfNwTPsrMktBFxPYr3AEfKL0rcfezGdB46/kA5ovk8FyhD6MXFnkzL1gFQb5+pwz+eYN3xU3xhlgd6m+camZ1zYQypzDJLwFmTQBFrTF2RolZGlaZ+DOXLYf6EO8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=yrzB9l09; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="yrzB9l09" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CC82DC116C6; Fri, 27 Feb 2026 20:09:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1772222994; bh=5N9ATerv0OaDW11j0jD0bDVQgayVJDS/nufTwYczaIo=; h=Date:To:From:Subject:From; b=yrzB9l09H1CQppvp/dGGOUcTtuTdAEhZBhjRnW/NrW04iWnE2vZTBGzlet3HAX46L cAVnoCl0KBuVkkvCXOLAPW0j8EZd+5d1goA7ILMdLD4PMSr/b7Ow/TDneOZ0zyp3At dcOqEoh9BmrIFuH355+5PJC4jjI6mcOMmFFUYC/0= Date: Fri, 27 Feb 2026 12:09:54 -0800 To: mm-commits@vger.kernel.org,ziy@nvidia.com,willy@infradead.org,vbabka@suse.cz,usamaarif642@gmail.com,rppt@kernel.org,roman.gushchin@linux.dev,rientjes@google.com,paul.walmsley@sifive.com,palmer@dabbelt.com,osalvador@suse.de,muchun.song@linux.dev,mhocko@suse.com,lorenzo.stoakes@oracle.com,kernel@xen0n.name,harry.yoo@oracle.com,hannes@cmpxchg.org,fvdl@google.com,david@kernel.org,corbet@lwn.net,cl@gentwo.org,chenhuacai@kernel.org,bhe@redhat.com,aou@eecs.berkeley.edu,alex@ghiti.fr,kas@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-hugetlb-defer-vmemmap-population-for-bootmem-hugepages.patch added to mm-new branch Message-Id: <20260227200954.CC82DC116C6@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/hugetlb: defer vmemmap population for bootmem hugepages has been added to the -mm mm-new branch. Its filename is mm-hugetlb-defer-vmemmap-population-for-bootmem-hugepages.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-defer-vmemmap-population-for-bootmem-hugepages.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: "Kiryl Shutsemau (Meta)" Subject: mm/hugetlb: defer vmemmap population for bootmem hugepages Date: Fri, 27 Feb 2026 19:42:47 +0000 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(). Link: https://lkml.kernel.org/r/20260227194302.274384-10-kas@kernel.org Signed-off-by: Kiryl Shutsemau (Meta) Cc: Albert Ou Cc: Alexandre Ghiti Cc: Baoquan He Cc: Christoph Lameter Cc: David Hildenbrand (arm) Cc: David Rientjes Cc: Frank van der Linden Cc: Harry Yoo Cc: Huacai Chen Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Oscar Salvador Cc: Palmer Dabbelt Cc: Paul Walmsley Cc: Roman Gushchin Cc: Usama Arif Cc: Vlastimil Babka Cc: WANG Xuerui Cc: Zi Yan Signed-off-by: Andrew Morton --- include/linux/mm.h | 2 - mm/hugetlb_vmemmap.c | 37 +++++++++++++--------------- mm/sparse-vmemmap.c | 53 ----------------------------------------- 3 files changed, 18 insertions(+), 74 deletions(-) --- a/include/linux/mm.h~mm-hugetlb-defer-vmemmap-population-for-bootmem-hugepages +++ a/include/linux/mm.h @@ -4474,8 +4474,6 @@ int vmemmap_populate(unsigned long start struct vmem_altmap *altmap); int vmemmap_populate_hvo(unsigned long start, unsigned long end, int node, unsigned long headsize); -int vmemmap_undo_hvo(unsigned long start, unsigned long end, int node, - unsigned long headsize); void vmemmap_wrprotect_hvo(unsigned long start, unsigned long end, int node, unsigned long headsize); void vmemmap_populate_print_last(void); --- a/mm/hugetlb_vmemmap.c~mm-hugetlb-defer-vmemmap-population-for-bootmem-hugepages +++ a/mm/hugetlb_vmemmap.c @@ -790,7 +790,6 @@ void __init hugetlb_vmemmap_init_early(i { unsigned long psize, paddr, section_size; unsigned long ns, i, pnum, pfn, nr_pages; - unsigned long start, end; struct huge_bootmem_page *m = NULL; void *map; @@ -808,14 +807,6 @@ void __init hugetlb_vmemmap_init_early(i paddr = virt_to_phys(m); pfn = PHYS_PFN(paddr); map = pfn_to_page(pfn); - start = (unsigned long)map; - end = start + nr_pages * sizeof(struct page); - - if (vmemmap_populate_hvo(start, end, nid, - HUGETLB_VMEMMAP_RESERVE_SIZE) < 0) - continue; - - memmap_boot_pages_add(HUGETLB_VMEMMAP_RESERVE_SIZE / PAGE_SIZE); pnum = pfn_to_section_nr(pfn); ns = psize / section_size; @@ -850,28 +841,36 @@ void __init hugetlb_vmemmap_init_late(in h = m->hstate; pfn = PHYS_PFN(phys); nr_pages = pages_per_huge_page(h); + map = pfn_to_page(pfn); + start = (unsigned long)map; + end = start + nr_pages * sizeof(struct page); if (!hugetlb_bootmem_page_zones_valid(nid, m)) { /* * Oops, the hugetlb page spans multiple zones. - * Remove it from the list, and undo HVO. + * Remove it from the list, and populate it normally. */ list_del(&m->list); - map = pfn_to_page(pfn); - - start = (unsigned long)map; - end = start + nr_pages * sizeof(struct page); - - vmemmap_undo_hvo(start, end, nid, - HUGETLB_VMEMMAP_RESERVE_SIZE); - nr_mmap = end - start - HUGETLB_VMEMMAP_RESERVE_SIZE; + vmemmap_populate(start, end, nid, NULL); + nr_mmap = end - start; memmap_boot_pages_add(DIV_ROUND_UP(nr_mmap, PAGE_SIZE)); memblock_phys_free(phys, huge_page_size(h)); continue; - } else + } + + if (vmemmap_populate_hvo(start, end, nid, + HUGETLB_VMEMMAP_RESERVE_SIZE) < 0) { + /* Fallback if HVO population fails */ + vmemmap_populate(start, end, nid, NULL); + nr_mmap = end - start; + } else { m->flags |= HUGE_BOOTMEM_ZONES_VALID; + nr_mmap = HUGETLB_VMEMMAP_RESERVE_SIZE; + } + + memmap_boot_pages_add(DIV_ROUND_UP(nr_mmap, PAGE_SIZE)); } } #endif --- a/mm/sparse-vmemmap.c~mm-hugetlb-defer-vmemmap-population-for-bootmem-hugepages +++ a/mm/sparse-vmemmap.c @@ -303,59 +303,6 @@ int __meminit vmemmap_populate_basepages } /* - * Undo populate_hvo, and replace it with a normal base page mapping. - * Used in memory init in case a HVO mapping needs to be undone. - * - * This can happen when it is discovered that a memblock allocated - * hugetlb page spans multiple zones, which can only be verified - * after zones have been initialized. - * - * We know that: - * 1) The first @headsize / PAGE_SIZE vmemmap pages were individually - * allocated through memblock, and mapped. - * - * 2) The rest of the vmemmap pages are mirrors of the last head page. - */ -int __meminit vmemmap_undo_hvo(unsigned long addr, unsigned long end, - int node, unsigned long headsize) -{ - unsigned long maddr, pfn; - pte_t *pte; - int headpages; - - /* - * Should only be called early in boot, so nothing will - * be accessing these page structures. - */ - WARN_ON(!early_boot_irqs_disabled); - - headpages = headsize >> PAGE_SHIFT; - - /* - * Clear mirrored mappings for tail page structs. - */ - for (maddr = addr + headsize; maddr < end; maddr += PAGE_SIZE) { - pte = virt_to_kpte(maddr); - pte_clear(&init_mm, maddr, pte); - } - - /* - * Clear and free mappings for head page and first tail page - * structs. - */ - for (maddr = addr; headpages-- > 0; maddr += PAGE_SIZE) { - pte = virt_to_kpte(maddr); - pfn = pte_pfn(ptep_get(pte)); - pte_clear(&init_mm, maddr, pte); - memblock_phys_free(PFN_PHYS(pfn), PAGE_SIZE); - } - - flush_tlb_kernel_range(addr, end); - - return vmemmap_populate(addr, end, node, NULL); -} - -/* * Write protect the mirrored tail page structs for HVO. This will be * called from the hugetlb code when gathering and initializing the * memblock allocated gigantic pages. The write protect can't be _ Patches currently in -mm which might be from kas@kernel.org are mm-move-max_folio_order-definition-to-mmzoneh.patch mm-change-the-interface-of-prep_compound_tail.patch mm-rename-the-compound_head-field-in-the-struct-page-to-compound_info.patch mm-move-set-clear_compound_head-next-to-compound_head.patch riscv-mm-align-vmemmap-to-maximal-folio-size.patch loongarch-mm-align-vmemmap-to-maximal-folio-size.patch mm-rework-compound_head-for-power-of-2-sizeofstruct-page.patch mm-sparse-check-memmap-alignment-for-compound_info_has_mask.patch mm-hugetlb-defer-vmemmap-population-for-bootmem-hugepages.patch mm-hugetlb-refactor-code-around-vmemmap_walk.patch x86-vdso-undefine-config_hugetlb_page_optimize_vmemmap-for-vdso32.patch mm-hugetlb-remove-fake-head-pages.patch mm-drop-fake-head-checks.patch hugetlb-remove-vmemmap_synchronize_rcu.patch mm-hugetlb-remove-hugetlb_optimize_vmemmap_key-static-key.patch mm-remove-the-branch-from-compound_head.patch hugetlb-update-vmemmap_deduprst.patch mm-slab-use-compound_head-in-page_slab.patch