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Thu, 13 Aug 2026 16:10:32 +0000 X-Migadu-Flow: FLOW_OUT Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Thu, 13 Aug 2026 17:10:26 +0100 Message-Id: Cc: "Borislav Petkov" , "Dave Hansen" , "Peter Zijlstra" , "Andrew Morton" , "David Hildenbrand" , "Vlastimil Babka" , "Wei Xu" , "Johannes Weiner" , "Zi Yan" , "Lorenzo Stoakes" , , , , "Sumit Garg" , "Will Deacon" , , "Kalyazin, Nikita" , , "Itazuri, Takahiro" , "Andy Lutomirski" , "David Kaplan" , "Thomas Gleixner" , "Yosry Ahmed" , "Patrick Bellasi" , "Reiji Watanabe" , "Sean Christopherson" Subject: Re: [PATCH v3 07/26] x86/mm: introduce mm-local region From: "Brendan Jackman" To: "Mike Rapoport" , "Brendan Jackman" X-Mailer: aerc 0.21.0 References: <20260726-page_alloc-unmapped-v3-0-6f5729aa9832@google.com> <20260726-page_alloc-unmapped-v3-7-6f5729aa9832@google.com> In-Reply-To: X-Rspam-User: X-Stat-Signature: ici8ip3t5yjs7p6rq6codboc5hhio4w6 X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: BC13640002 X-HE-Tag: 1786637443-455574 X-HE-Meta: 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 B1Qe9/oA SF8jfFVW9JW7Ct4/+xXtLs5WRUwmawO1REWQkwp/2Z3hYKiB0vJOTb55ME9CwC2bHlndOnkFulaMIBAbK8H1QkfhYmuZNe/HwMEqid/Aq5gVFZ2hPKkDBXWhMUO6n5cEXhMShS2d9G2qFK6AAReQo79o1rRUkBzkuIQ/BsGvWVyTeVwEYVGoi/xNnNfsEnglZa0neztoVlbreIEKn6XBw4AQbTow/utDxABp24wBuf/byh4jThN3zIicKvkr9r5TvBhm/tJ/Ny94vz+r0mIgzAHw0/b9kSkhUuKAKT3EfRJcuH8eMzhuACHBR8g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun Aug 2, 2026 at 5:27 PM BST, Mike Rapoport wrote: ... >> +#if defined(CONFIG_MITIGATION_PAGE_TABLE_ISOLATION) && defined(CONFIG_X= 86_PAE) >> +static inline pmd_t *pgd_to_pmd_walk(pgd_t *pgd, unsigned long va) > > There's very similar mm_find_pmd() in mm/rmap.c and I bet a bunch of othe= r > places walk from PGD to PMD and return PMD in the end. > > Can we put this function into, say, mm/pgtable-generic.c? > Finding all the places that do such walk and sticking it there should not > be a part of this set IMNHO, but having it in the generic code is a good > start for a future cleanup. Yeah, this is the kinda subtlety I always run into when trying to play with pagetable code, and I end up being timid. The thing is that mm_find_pmd() bails when it finds a non-present entry. I think in this case it's fine, so yeah we could at least move mm_find_pmd(), change the mm arg to a pgd_t*, rename it, and call it from here. >> +{ >> + p4d_t *p4d; >> + pud_t *pud; >> + >> + if (pgd->pgd =3D=3D 0) >> + return NULL; >> + >> + p4d =3D p4d_offset(pgd, va); >> + if (p4d_none(*p4d)) >> + return NULL; >> + >> + pud =3D pud_offset(p4d, va); >> + if (pud_none(*pud)) >> + return NULL; >> + >> + return pmd_offset(pud, va); >> +}