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Wed, 10 Sep 2025 02:47:55 -0700 (PDT) Received: from [192.168.1.140] ([85.235.12.238]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5680c424fa5sm1139655e87.25.2025.09.10.02.47.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Sep 2025 02:47:55 -0700 (PDT) From: Linus Walleij Date: Wed, 10 Sep 2025 11:47:52 +0200 Subject: [PATCH] RFC: ARM: drop support for HIGHPTE Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250910-arm-remove-high-pte-v1-1-d0899882815f@linaro.org> X-B4-Tracking: v=1; b=H4sIAEdJwWgC/x3MOwqAMBBF0a3I1A5ExYBuRSyiPpMp/DAREYJ7N 1ie4t5EESqI1BeJFLdEOfaMqixoDm73YFmyqTZ1a7rKsNONFdtxg4P4wOcFtnBLN1tMTWMpl6d ilee/DuP7fg5UmHtlAAAA X-Change-ID: 20250910-arm-remove-high-pte-6ead9c6eb336 To: Russell King Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Russell King , Matthew Wilcox , Arnd Bergmann , Linus Walleij X-Mailer: b4 0.14.2 Matthew Wilcox suggests HIGHPTE is a burden for the kernel MM, and only one ARM system (vt8500) is currently using it. This deletes the use of HIGHPTE in ARM32 clearing the way to remove the feature altogether. It was introduced in commit 65cec8e3db60 "ARM: implement highpte" in 2009, so this RFC is intended as a discussion item to check if it is still a desired feature 16 years later or if we can get rid of it. To: Russell King To: Matthew Wilcox To: Arnd Bergmann Link: https://lore.kernel.org/linux-arm-kernel/aMDYdp3H-yOHU1Pm@casper.infr= adead.org/ Signed-off-by: Linus Walleij --- arch/arm/Kconfig | 11 ----------- arch/arm/configs/vt8500_v6_v7_defconfig | 1 - arch/arm/include/asm/pgalloc.h | 8 +------- 3 files changed, 1 insertion(+), 19 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index b1f3df39ed4068f215a3460d5c4e021136438eaa..5545583946a2433f86a5ba2d6ad= e34f5e931ae74 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1229,17 +1229,6 @@ config HIGHMEM =20 If unsure, say n. =20 -config HIGHPTE - bool "Allocate 2nd-level pagetables from highmem" if EXPERT - depends on HIGHMEM - 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/configs/vt8500_v6_v7_defconfig b/arch/arm/configs/vt8= 500_v6_v7_defconfig index 41607a84abc85adfc9d8d2d520354576e1e274d2..a91e6547378136b3e1264aaddca= c7d6ddb66987d 100644 --- a/arch/arm/configs/vt8500_v6_v7_defconfig +++ b/arch/arm/configs/vt8500_v6_v7_defconfig @@ -10,7 +10,6 @@ CONFIG_ARM_ERRATA_775420=3Dy CONFIG_HAVE_ARM_ARCH_TIMER=3Dy CONFIG_AEABI=3Dy CONFIG_HIGHMEM=3Dy -CONFIG_HIGHPTE=3Dy CONFIG_ARM_APPENDED_DTB=3Dy CONFIG_ARM_ATAG_DTB_COMPAT=3Dy CONFIG_VFP=3Dy diff --git a/arch/arm/include/asm/pgalloc.h b/arch/arm/include/asm/pgalloc.h index a17f01235c29c0dc619c0929aa761df861a5dd2d..ef6cb3e6d179e63c7edbcaf69e6= b21847b354a0f 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; } =20 -#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; =20 - pte =3D __pte_alloc_one(mm, GFP_PGTABLE_USER | PGTABLE_HIGHMEM); + pte =3D __pte_alloc_one(mm, GFP_PGTABLE_USER); if (!pte) return NULL; if (!PageHighMem(pte)) --- base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585 change-id: 20250910-arm-remove-high-pte-6ead9c6eb336 Best regards, --=20 Linus Walleij