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b=UKlE9Vcx+ibmwZLg8uTgDhwFr1MQKvh4COZdEA29Zk4+a0WEHLRHV+s0GW3A7iSHe 3HD4/3g/v7nfvJumkgVcBV6bvBu1SfB7gaIyD4dF2MbygEzfAackvuElPeKYN09ozI vNr2sH/bIqJTIJ/1Sh8QjXQC23L52Z4YVCtA2hQVxOb8dltXl6qMLWG7NCwcIO0/qd Cd1Or+kj2bGVCdnHe9tbzDuwafP4AW8GXLqzKcY9q8OjsvcroCAcjGJeEecCteY5vk 2NzvhxfvKva7KE8T2F6nN/SVnRI+4YH8G/vz9LxdcQS01ioUBR5erT0qJtsRngShCP EDSvUcG27ePBg== Date: Fri, 31 Jul 2026 23:59:35 +0000 From: Yosry Ahmed To: Brendan Jackman Cc: Borislav Petkov , Dave Hansen , Peter Zijlstra , Andrew Morton , David Hildenbrand , Vlastimil Babka , Mike Rapoport , Wei Xu , Johannes Weiner , Zi Yan , Lorenzo Stoakes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, Sumit Garg , Will Deacon , rientjes@google.com, "Kalyazin, Nikita" , patrick.roy@linux.dev, "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 Message-ID: References: <20260726-page_alloc-unmapped-v3-0-6f5729aa9832@google.com> <20260726-page_alloc-unmapped-v3-5-6f5729aa9832@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260726-page_alloc-unmapped-v3-5-6f5729aa9832@google.com> X-Rspam-User: X-Rspamd-Queue-Id: 8B2E8160008 X-Rspamd-Server: rspam01 X-Stat-Signature: k89x5ipthnsi6azssbkzyiahu4saq4pu X-HE-Tag: 1785542378-633832 X-HE-Meta: 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 gDPCaE2G cpTPRCjG8NOlr+ZrbrbXP2sORPWH3xFuUoGWHYojacytEHAgTJ8zG6+cutfN+j05TMKQJnFeRZHOMpYxeY0D17S8LWoSK7HRmAKoBuJXT0FgIWSwI6e3iC0kj3pdsjQRTOS0QNDryV8Z5lD/dz57IJe6NXlGJdCEGw4PUXdoXW9XT0/C/X+Yr/EHU6s/uI+Zn0JtWyRhIKhX64gY/64KLr3Y9nl7n2N1rR+HASYC03BMFMTozU40WCxtY42+tOrbg7IuVj753zbBcZDtJ2BmXPEbHSyIoVpWjUC+E/++f5fYOOjYWBq6WcZj0bw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 new > file, move them as a separate patch for easy review. > > The comments have style violations (personal pronouns etc), do not fix > them as this is just code movement. > > No functional change intended. > > 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/mmu_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, unsigned long va) static inline int mm_local_map_to_user(struct mm_struct *mm) { - BUILD_BUG_ON(!PREALLOCATED_PMDS); pgd_t *k_pgd = pgd_offset(mm, MM_LOCAL_BASE_ADDR); pgd_t *u_pgd = 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_struct *mm) k_pmd = pgd_to_pmd_walk(k_pgd, MM_LOCAL_BASE_ADDR); u_pmd = 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. */