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b=QXSfiJSWVRJXBEP0SekW5iZErSus3IhESAmYYSoJ6gFHXzQa0SEJVUdZvq5ukRZDB zIPjxW4etzEDjGqnuJfKbNVNZxoFMvzhZDS9m81YSp76lOMl2N4adQE3QXfqhBMfvA 9l5NsWktPRODSt3io3E2kVXyTOFCfLLIH6vAn1opAIncFXGuHBQ6cxmjLB2/4yrd/K 8UPGjOH77gUkh2AZC4I0bJ+fOkkAs2wHOmfKqa1zHKPt6SB7Ec0zuKXHtEtOnpQS1O 7Akv52un3uHhlY5kipQTVVs4WyWo7GPo7w0EOGpELT6Sn1Y9ieNLHwwZ5DbqObaFtC 55nWb1rCIF09g== Date: Thu, 12 Nov 2026 13:47:23 +0200 From: Mike Rapoport To: Arnd Bergmann Cc: linux-mm@kvack.org, Arnd Bergmann , Andrew Morton , Andreas Larsson , "Christophe Leroy (CS GROUP)" , Dave Hansen , "David Hildenbrand (Arm)" , Jason Gunthorpe , Linus Walleij , "Lorenzo Stoakes (ARM)" , Matthew Wilcox , Malin Jonsson , Richard Weinberger , Russell King , linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: Re: [PATCH v2 3/6] ARM: drop CONFIG_HIGHPTE support Message-ID: References: <20261112112528.1116405-1-arnd@kernel.org> <20261112112528.1116405-4-arnd@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261112112528.1116405-4-arnd@kernel.org> X-Rspamd-Queue-Id: 02B271C0004 X-Rspamd-Server: rspam12 X-Stat-Signature: 6qzfzk9c4unu1h8agdmy3jduje9wgzn1 X-Rspam-User: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794484052-372856 X-HE-Meta: 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 pOzWIMnX xsmlstgG6YwS+TJf0yhcIp/Jn2aFLC4hWUx+RjoslhzGeEKpm70ICVqMR8tBeyOHaPPH1zbrRbAZ1gxyK5hBIh/V8gcXMWwdtNsbPlD4IdCmNGcngl2UfzXK9IcDSD8iNDWTbafh1pdmKMHfmq+7ksQGi1DRd76q1E4Acc7kDR8M2JIoAiKYBzMZT3W9Y5/L/jttkPGjzMRLASQKtLIAkzW8Ys5pWlft/DeZbYxW2hetTFktVmkNSCna0OkTJomKQN75O2+XZUGbP4eYKlapeQcTZzD97X3ZFJOcx+JHm18saSNcn9mu3lgS2j2VWbEIzMe9B7TKLMYPRmd9DOKiTcgQ4x/0ToTWJG8HAMbTNBYs1Fmb4IH/VcW4Y8JgRhhGnLxbXg5/+Sy0iRLI9rvyTBbh2C1dSFORj8hit1/+bxWIuoPM2cfC6ZZ+0iLVGErpYPoyUI3kLG75zbeIZxg3mi/r80W0jVt6Yus3T Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Nov 12, 2026 at 12:25:25PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann > > CONFIG_HIGHPTE was added in linux-2.6.32, a few years before 64-bit > support. At the time it made sense, as the CONFIG_ARM_LPAE option allowed > systems with 16GB of memory that made lowmem a particularly scarce > resource, and the HIGHPTE implementation gave feature parity with 32-bit > x86 and frv machines. > > Since Arm is the last architecture remaining that uses this, and almost > no 32-bit machines support more than 4GB of RAM, the cost of continuing > to maintain HIGHPTE seems unjustified, so remove it here to allow > simplifying the generic page table handling. > > Link: https://lore.kernel.org/lkml/20241204103042.1904639-8-arnd@kernel.org/T/#u > Signed-off-by: Arnd Bergmann > --- > I sent a patch to drop HIGHPTE support on x86 today, see > https://lore.kernel.org/lkml/20241210144945.2325330-9-arnd@kernel.org/T/#u > > If that one gets merged, we can merge this one instead of the one > that makes HIGHPTE depend on !PREEMPT_RT, but if we decide against > the x86 change, then we probably don't want this one either. > > Signed-off-by: Arnd Bergmann > --- > arch/arm/Kconfig | 11 ----------- > arch/arm/include/asm/pgalloc.h | 8 +------- > 2 files changed, 1 insertion(+), 18 deletions(-) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index fd01ccab9c12..fc66d52d847e 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -1225,17 +1225,6 @@ config HIGHMEM > > If unsure, say n. > > -config HIGHPTE > - bool "Allocate 2nd-level pagetables from highmem" if EXPERT > - depends on HIGHMEM && !PREEMPT_RT > - default y > - help > - The VM uses one page of physical memory for each page table. > - For systems with a lot of processes, this can use a lot of > - precious low memory, eventually leading to low memory being > - consumed by page tables. Setting this option will allow > - user-space 2nd level page tables to reside in high memory. > - > config ARM_PAN > bool "Enable privileged no-access" > depends on MMU > diff --git a/arch/arm/include/asm/pgalloc.h b/arch/arm/include/asm/pgalloc.h > index a17f01235c29..ef6cb3e6d179 100644 > --- a/arch/arm/include/asm/pgalloc.h > +++ b/arch/arm/include/asm/pgalloc.h > @@ -85,18 +85,12 @@ pte_alloc_one_kernel(struct mm_struct *mm) > return pte; > } > > -#ifdef CONFIG_HIGHPTE > -#define PGTABLE_HIGHMEM __GFP_HIGHMEM > -#else > -#define PGTABLE_HIGHMEM 0 > -#endif > - > static inline pgtable_t > pte_alloc_one(struct mm_struct *mm) > { > struct page *pte; > > - pte = __pte_alloc_one(mm, GFP_PGTABLE_USER | PGTABLE_HIGHMEM); > + pte = __pte_alloc_one(mm, GFP_PGTABLE_USER); > if (!pte) > return NULL; > if (!PageHighMem(pte)) With HIGHPTE out this can be if (pte) clean_pte_table(pte); return pte; Otherwise Acked-by: Mike Rapoport (Microsoft) > -- > 2.53.0 > -- Sincerely yours, Mike.