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Thu, 13 Aug 2026 15:49:42 +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 16:49:40 +0100 Message-Id: Cc: "Borislav Petkov" , "Dave Hansen" , "Peter Zijlstra" , "Andrew Morton" , "David Hildenbrand" , "Vlastimil Babka" , "Mike Rapoport" , "Wei Xu" , "Johannes Weiner" , "Zi Yan" , "Lorenzo Stoakes" , , , , "Sumit Garg" , "Will Deacon" , , "Kalyazin, Nikita" , , "Itazuri, Takahiro" , "Andy Lutomirski" , "David Kaplan" , "Thomas Gleixner" , "Patrick Bellasi" , "Reiji Watanabe" , "Sean Christopherson" Subject: Re: [PATCH v3 05/26] x86: move PAE PMD preallocation defines to header From: "Brendan Jackman" To: "Yosry Ahmed" , "Brendan Jackman" X-Mailer: aerc 0.21.0 References: <20260726-page_alloc-unmapped-v3-0-6f5729aa9832@google.com> <20260726-page_alloc-unmapped-v3-5-6f5729aa9832@google.com> In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: C41EFC0008 X-Rspamd-Server: rspam07 X-Stat-Signature: 436m9q13p7hot469erwj6e98s5nted95 X-HE-Tag: 1786636183-679936 X-HE-Meta: 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 nxSL4tXa 9WzP2PemAxogAkWmyJIieEZwhSuJafJyQJ+0ClameRxdPJanBqR90/VS6D8ZQmaG6pWBbrJpbW+pPW+ynHV3CtRTSMgiNa2oxZQ36XI2vLLtOYjYoOE07+hyBsUyKSlOsyjPAzEuAiPrEvZzcjVzTyoDL/Zed6zY904gHLnu7Fdxxf9uR8+zF9t89LvdO2UcLt7cC9pl6o6HC+pD71Lm6FWcXuIe5E9vMx+vduBRUWeoBSYkzStQ4eh6LRlrRJIjLKuI16HrBlOS5dg0bY+doek+9edJDas4u3/hP/qEQiN+eY/NzAO3wuWPI1oc+vtK95yCdeE+LkUzh2WY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat Aug 1, 2026 at 12:59 AM BST, Yosry Ahmed wrote: > On Sun, Jul 26, 2026 at 10:22:38PM +0000, Brendan Jackman wrote: >> In a subsequent patch these defines will need to be referenced from a ne= w >> file, move them as a separate patch for easy review. >>=20 >> The comments have style violations (personal pronouns etc), do not fix >> them as this is just code movement. >>=20 >> No functional change intended. >>=20 >> Signed-off-by: Brendan Jackman > > AFAICT, this is only needed to expose PREALLOCATED_PMDS for > mm_local_map_to_user() in patch #7. The only usage is a BUILD_BUG_ON(). > > I wonder if it would be more preferrable to keep the definitions in > pgtable.c and add a runtime check instead in mm_local_map_to_user(), > something like: > > diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mm= u_context.h > index 09b8d8e6a56ea..15055cb80092c 100644 > --- a/arch/x86/include/asm/mmu_context.h > +++ b/arch/x86/include/asm/mmu_context.h > @@ -268,7 +268,6 @@ static inline pmd_t *pgd_to_pmd_walk(pgd_t *pgd, unsi= gned long va) > > static inline int mm_local_map_to_user(struct mm_struct *mm) > { > - BUILD_BUG_ON(!PREALLOCATED_PMDS); > pgd_t *k_pgd =3D pgd_offset(mm, MM_LOCAL_BASE_ADDR); > pgd_t *u_pgd =3D kernel_to_user_pgdp(k_pgd); > pmd_t *k_pmd, *u_pmd; > @@ -277,6 +276,9 @@ static inline int mm_local_map_to_user(struct mm_stru= ct *mm) > k_pmd =3D pgd_to_pmd_walk(k_pgd, MM_LOCAL_BASE_ADDR); > u_pmd =3D pgd_to_pmd_walk(u_pgd, MM_LOCAL_BASE_ADDR); > > + if (WARN_ON_ONCE(!k_pmd || !u_pmd)) > + return -EINVAL; > + > BUILD_BUG_ON(MM_LOCAL_END_ADDR - MM_LOCAL_BASE_ADDR > PMD_SIZE); > > /* Preallocate the PTE table so it can be shared. */ Yeah, I'd say that's fine. Will get back to you if I find another reason why I thought the move was necessary...