kernel.git/arch/arm64/mm/flush.c, branch master

mm: introduce memdesc_flags_t

2025-09-13T23:55:07Z

Patch series "Add and use memdesc_flags_t". At some point struct page will be separated from struct slab and struct folio. This is a step towards that by introducing a type for the 'flags' word of all three structures. This gives us a certain amount of type safety by establishing that some of these unsigned longs are different from other unsigned longs in that they contain things like node ID, section number and zone number in the upper bits. That lets us have functions that can be easily called by anyone who has a slab, folio or page (but not easily by anyone else) to get the node or zone. There's going to be some unusual merge problems with this as some odd bits of the kernel decide they want to print out the flags value or something similar by writing page->flags and now they'll need to write page->flags.f instead. That's most of the churn here. Maybe we should be removing these things from the debug output? This patch (of 11): Wrap the unsigned long flags in a typedef. In upcoming patches, this will provide a strong hint that you can't just pass a random unsigned long to functions which take this as an argument. [willy@infradead.org: s/flags/flags.f/ in several architectures] Link: https://lkml.kernel.org/r/aKMgPRLD-WnkPxYm@casper.infradead.org [nicola.vetrini@gmail.com: mips: fix compilation error] Link: https://lore.kernel.org/lkml/CA+G9fYvkpmqGr6wjBNHY=dRp71PLCoi2341JxOudi60yqaeUdg@mail.gmail.com/ Link: https://lkml.kernel.org/r/20250825214245.1838158-1-nicola.vetrini@gmail.com Link: https://lkml.kernel.org/r/20250805172307.1302730-1-willy@infradead.org Link: https://lkml.kernel.org/r/20250805172307.1302730-2-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Matthew Wilcox (Oracle) Acked-by: Zi Yan Cc: Shakeel Butt Signed-off-by: Andrew Morton

arm64: implement the new page table range API

2023-08-24T23:20:20Z

Add set_ptes(), update_mmu_cache_range() and flush_dcache_folio(). Change the PG_dcache_clean flag from being per-page to per-folio. Link: https://lkml.kernel.org/r/20230802151406.3735276-11-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Catalin Marinas Acked-by: Mike Rapoport (IBM) Signed-off-by: Andrew Morton

arm64: flush: include linux/libnvdimm.h

2023-05-25T16:44:02Z

The two cache management functions are declared in libnvdimm.h but provided by architecture specific code. Without including the header, this causes a W=1 warning: arch/arm64/mm/flush.c:96:6: error: no previous prototype for 'arch_wb_cache_pmem' [-Werror=missing-prototypes] arch/arm64/mm/flush.c:104:6: error: no previous prototype for 'arch_invalidate_pmem' [-Werror=missing-prototypes] Signed-off-by: Arnd Bergmann Reviewed-by: Kees Cook Acked-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20230516160642.523862-12-arnd@kernel.org Signed-off-by: Catalin Marinas

mm: hugetlb_vmemmap: delete hugetlb_optimize_vmemmap_enabled()

2022-08-09T01:06:42Z

Patch series "Simplify hugetlb vmemmap and improve its readability", v2. This series aims to simplify hugetlb vmemmap and improve its readability. This patch (of 8): The name hugetlb_optimize_vmemmap_enabled() a bit confusing as it tests two conditions (enabled and pages in use). Instead of coming up to an appropriate name, we could just delete it. There is already a discussion about deleting it in thread [1]. There is only one user of hugetlb_optimize_vmemmap_enabled() outside of hugetlb_vmemmap, that is flush_dcache_page() in arch/arm64/mm/flush.c. However, it does not need to call hugetlb_optimize_vmemmap_enabled() in flush_dcache_page() since HugeTLB pages are always fully mapped and only head page will be set PG_dcache_clean meaning only head page's flag may need to be cleared (see commit cf5a501d985b). So it is easy to remove hugetlb_optimize_vmemmap_enabled(). Link: https://lore.kernel.org/all/c77c61c8-8a5a-87e8-db89-d04d8aaab4cc@oracle.com/ [1] Link: https://lkml.kernel.org/r/20220628092235.91270-2-songmuchun@bytedance.com Signed-off-by: Muchun Song Reviewed-by: Oscar Salvador Reviewed-by: Mike Kravetz Reviewed-by: Catalin Marinas Cc: Will Deacon Cc: Anshuman Khandual Cc: David Hildenbrand Cc: Jonathan Corbet Cc: Xiongchun Duan Signed-off-by: Andrew Morton

mm: hugetlb_vmemmap: cleanup CONFIG_HUGETLB_PAGE_FREE_VMEMMAP*

2022-04-29T06:16:15Z

The word of "free" is not expressive enough to express the feature of optimizing vmemmap pages associated with each HugeTLB, rename this keywork to "optimize". In this patch , cheanup configs to make code more expressive. Link: https://lkml.kernel.org/r/20220404074652.68024-4-songmuchun@bytedance.com Signed-off-by: Muchun Song Cc: Mike Kravetz Cc: David Hildenbrand Signed-off-by: Andrew Morton

mm: hugetlb_vmemmap: cleanup hugetlb_free_vmemmap_enabled*

2022-04-29T06:16:15Z

The word of "free" is not expressive enough to express the feature of optimizing vmemmap pages associated with each HugeTLB, rename this keywork to "optimize". In this patch , cheanup the static key and hugetlb_free_vmemmap_enabled() to make code more expressive. Link: https://lkml.kernel.org/r/20220404074652.68024-3-songmuchun@bytedance.com Signed-off-by: Muchun Song Cc: David Hildenbrand Cc: Mike Kravetz Signed-off-by: Andrew Morton

arm64: mm: hugetlb: enable HUGETLB_PAGE_FREE_VMEMMAP for arm64

2022-04-29T06:16:03Z

The feature of minimizing overhead of struct page associated with each HugeTLB page aims to free its vmemmap pages (used as struct page) to save memory, where is ~14GB/16GB per 1TB HugeTLB pages (2MB/1GB type). In short, when a HugeTLB page is allocated or freed, the vmemmap array representing the range associated with the page will need to be remapped. When a page is allocated, vmemmap pages are freed after remapping. When a page is freed, previously discarded vmemmap pages must be allocated before remapping. More implementations and details can be found here [1]. The infrastructure of freeing vmemmap pages associated with each HugeTLB page is already there, we can easily enable HUGETLB_PAGE_FREE_VMEMMAP for arm64, the only thing to be fixed is flush_dcache_page() . flush_dcache_page() need to be adapted to operate on the head page's flags since the tail vmemmap pages are mapped with read-only after the feature is enabled (clear operation is not permitted). There was some discussions about this in the thread [2], but there was no conclusion in the end. And I copied the concern proposed by Anshuman to here and explain why those concern is superfluous. It is safe to enable it for x86_64 as well as arm64. 1st concern: ''' But what happens when a hot remove section's vmemmap area (which is being teared down) is nearby another vmemmap area which is either created or being destroyed for HugeTLB alloc/free purpose. As you mentioned HugeTLB pages inside the hot remove section might be safe. But what about other HugeTLB areas whose vmemmap area shares page table entries with vmemmap entries for a section being hot removed ? Massive HugeTLB alloc /use/free test cycle using memory just adjacent to a memory hotplug area, which is always added and removed periodically, should be able to expose this problem. ''' Answer: At the time memory is removed, all HugeTLB pages either have been migrated away or dissolved. So there is no race between memory hot remove and free_huge_page_vmemmap(). Therefore, HugeTLB pages inside the hot remove section is safe. Let's talk your question "what about other HugeTLB areas whose vmemmap area shares page table entries with vmemmap entries for a section being hot removed ?", the question is not established. The minimal granularity size of hotplug memory 128MB (on arm64, 4k base page), any HugeTLB smaller than 128MB is within a section, then, there is no share PTE page tables between HugeTLB in this section and ones in other sections and a HugeTLB page could not cross two sections. In this case, the section cannot be freed. Any HugeTLB bigger than 128MB (section size) whose vmemmap pages is an integer multiple of 2MB (PMD-mapped). As long as: 1) HugeTLBs are naturally aligned, power-of-two sizes 2) The HugeTLB size >= the section size 3) The HugeTLB size >= the vmemmap leaf mapping size Then a HugeTLB will not share any leaf page table entries with *anything else*, but will share intermediate entries. In this case, at the time memory is removed, all HugeTLB pages either have been migrated away or dissolved. So there is also no race between memory hot remove and free_huge_page_vmemmap(). 2nd concern: ''' differently, not sure if ptdump would require any synchronization. Dumping an wrong value is probably okay but crashing because a page table entry is being freed after ptdump acquired the pointer is bad. On arm64, ptdump() is protected against hotremove via [get|put]_online_mems(). ''' Answer: The ptdump should be fine since vmemmap_remap_free() only exchanges PTEs or splits the PMD entry (which means allocating a PTE page table). Both operations do not free any page tables (PTE), so ptdump cannot run into a UAF on any page tables. The worst case is just dumping an wrong value. [1] https://lore.kernel.org/all/20210510030027.56044-1-songmuchun@bytedance.com/ [2] https://lore.kernel.org/all/20210518091826.36937-1-songmuchun@bytedance.com/ [songmuchun@bytedance.com: restructure the code comment inside flush_dcache_page()] Link: https://lkml.kernel.org/r/20220414072646.21910-1-songmuchun@bytedance.com Link: https://lkml.kernel.org/r/20220331065640.5777-2-songmuchun@bytedance.com Signed-off-by: Muchun Song Reviewed-by: Barry Song Tested-by: Barry Song Cc: Will Deacon Cc: David Hildenbrand Cc: Bodeddula Balasubramaniam Cc: Oscar Salvador Cc: Mike Kravetz Cc: David Rientjes Cc: Mark Rutland Cc: Catalin Marinas Cc: James Morse Cc: Xiongchun Duan Cc: Fam Zheng Signed-off-by: Andrew Morton

arm64: avoid flushing icache multiple times on contiguous HugeTLB

2022-03-07T21:42:34Z

When a contiguous HugeTLB page is mapped, set_pte_at() will be called CONT_PTES/CONT_PMDS times. Therefore, __sync_icache_dcache() will flush cache multiple times if the page is executable (to ensure the I-D cache coherency). However, the first flushing cache already covers subsequent cache flush operations. So only flusing cache for the head page if it is a HugeTLB page to avoid redundant cache flushing. In the next patch, it is also depends on this change since the tail vmemmap pages of HugeTLB is mapped with read-only meanning only head page struct can be modified. Signed-off-by: Muchun Song Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20220302084624.33340-1-songmuchun@bytedance.com Signed-off-by: Will Deacon

arm64: Rename arm64-internal cache maintenance functions

2021-05-25T18:27:49Z

Although naming across the codebase isn't that consistent, it tends to follow certain patterns. Moreover, the term "flush" isn't defined in the Arm Architecture reference manual, and might be interpreted to mean clean, invalidate, or both for a cache. Rename arm64-internal functions to make the naming internally consistent, as well as making it consistent with the Arm ARM, by specifying whether it applies to the instruction, data, or both caches, whether the operation is a clean, invalidate, or both. Also specify which point the operation applies to, i.e., to the point of unification (PoU), coherency (PoC), or persistence (PoP). This commit applies the following sed transformation to all files under arch/arm64: "s/\b__flush_cache_range\b/caches_clean_inval_pou_macro/g;"\ "s/\b__flush_icache_range\b/caches_clean_inval_pou/g;"\ "s/\binvalidate_icache_range\b/icache_inval_pou/g;"\ "s/\b__flush_dcache_area\b/dcache_clean_inval_poc/g;"\ "s/\b__inval_dcache_area\b/dcache_inval_poc/g;"\ "s/__clean_dcache_area_poc\b/dcache_clean_poc/g;"\ "s/\b__clean_dcache_area_pop\b/dcache_clean_pop/g;"\ "s/\b__clean_dcache_area_pou\b/dcache_clean_pou/g;"\ "s/\b__flush_cache_user_range\b/caches_clean_inval_user_pou/g;"\ "s/\b__flush_icache_all\b/icache_inval_all_pou/g;" Note that __clean_dcache_area_poc is deliberately missing a word boundary check at the beginning in order to match the efistub symbols in image-vars.h. Also note that, despite its name, __flush_icache_range operates on both instruction and data caches. The name change here reflects that. No functional change intended. Acked-by: Mark Rutland Signed-off-by: Fuad Tabba Reviewed-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20210524083001.2586635-19-tabba@google.com Signed-off-by: Will Deacon

arm64: sync_icache_aliases to take end parameter instead of size

2021-05-25T18:27:49Z

To be consistent with other functions with similar names and functionality in cacheflush.h, cache.S, and cachetlb.rst, change to specify the range in terms of start and end, as opposed to start and size. No functional change intended. Reported-by: Will Deacon Acked-by: Mark Rutland Signed-off-by: Fuad Tabba Reviewed-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20210524083001.2586635-17-tabba@google.com Signed-off-by: Will Deacon