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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 4D434C000E X-Stat-Signature: g3mse46u8p9exfwmjrgm9mmir3fkndd8 X-Rspam-User: X-HE-Tag: 1748599419-401326 X-HE-Meta: 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 xkIL2mZw /HUpdiLUWpx1vNHtnVsbGBezMU42QKmEIuMlI+6ohIqIyMuHGb5LuRtAOuXaRRilxakuisWRLsOCK/g7oxLSsms6WdBY9F0BmkVnXAEwWi+3xm9eF06aB6ut7UsSlrsSt3NFqaklb6UmVmnoMLfyLYAYs+bptPSeN86Diz/wOcs5Nfw6scHZeBu5CaaLZaUQgp2uFolAC1bhsO4nXJHZ/hSXcY4hYcrcl7Ahj 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 30/05/2025 10:04, Dev Jain wrote: > This series paves the path to enable huge mappings in vmalloc space by > default on arm64. > For this we must ensure that we can handle any permission > games on vmalloc space. And the linear map :) > Currently, __change_memory_common() uses > apply_to_page_range() which does not support changing permissions for > leaf mappings. nit: A "leaf mapping" is the lowest level entry in the page tables for a given address - i.e. it maps an address to some actual memory rather than to another pgtable. It includes what the Arm ARM calls "page mappings" (PTE level) and "block mappings" (PMD/PUD/.. level). apply_to_page_range() does support page mappings, so saying it doesn't support leaf mappings is incorrect. It doesn't support block mappings. > We attempt to move away from this by using walk_page_range_novma(), > similar to what riscv does right now; however, it is the responsibility > of the caller to ensure that we do not pass a range, or split the range > covering a partial leaf mapping. > > This series is tied with Yang Shi's attempt [1] at using huge mappings > in the linear mapping in case the system supports BBML2, in which case > we will be able to split the linear mapping if needed without break-before-make. > Thus, Yang's series, IIUC, will be one such user of my series; suppose we > are changing permissions on a range of the linear map backed by PMD-hugepages, > then the sequence of operations should look like the following: > > split_range(start, (start + HPAGE_PMD_SIZE) & ~HPAGE_PMD_MASK); > split_range(end & ~HPAGE_PMD_MASK, end); I don't understand what the HPAGE_PMD_MASK twiddling is doing? That's not right. It's going to give you the offset within the 2M region. You just want: split_range(start) split_range(end) right? > __change_memory_common(start, end); > > However, this series can be used independently of Yang's; since currently > permission games are being played only on pte mappings (due to apply_to_page_range > not supporting otherwise), this series provides the mechanism for enabling > huge mappings for various kernel mappings like linear map and vmalloc. In other words, you are saying that this series is a prerequisite for Yang's series (and both are prerequisites for huge vmalloc by default). Your series adds a new capability that Yang's series will rely on (the ability to change permissions on block mappings). Thanks, Ryan > > [1] https://lore.kernel.org/all/20250304222018.615808-1-yang@os.amperecomputing.com/ > > Dev Jain (3): > mm: Allow pagewalk without locks > arm64: pageattr: Use walk_page_range_novma() to change memory > permissions > mm/pagewalk: Add pre/post_pte_table callback for lazy MMU on arm64 > > arch/arm64/mm/pageattr.c | 81 +++++++++++++++++++++++++++++++++++++--- > include/linux/pagewalk.h | 4 ++ > mm/pagewalk.c | 18 +++++++-- > 3 files changed, 94 insertions(+), 9 deletions(-) >