From nobody Wed Dec 17 14:23:22 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8C8E322FE07; Tue, 10 Dec 2024 16:06:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733846810; cv=none; b=oaKf/nEjQeyFlSbUyobybywYP20FA/vMcFL8fSlxypkOb/+ZrhcpmXr/j8V5c4mxqf9AE9LXlxQDby/EAmgP4k6wUgFcQePCbbnXq5q7jPYPDwY9HNYVBNWj3OvUWKdiNH9VEmcTqVsqomqykQl2nDapQMsH8IMTxAkL3kwblaM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733846810; c=relaxed/simple; bh=IDAs66loD46ejrDZgcdhA2wj912kFUy5s0hoLSzyXSk=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=c9ABv2zN7788WMftpTrPPU4jdL/2IctglHB5u1XOBNu+BzqZaSaZhUBaPwLlLZE/JLdee4Z/EOK0a4M6nXiba+8JbHfXchtapvH5GHBKnUeRx6928j3FASbh1TxQtzBy1IELDojGMXy9oxJjoSAgDxxHsdTNC7xgPAcjz7pJIEc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ADJHIkfi; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ADJHIkfi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D2AE5C4CEE1; Tue, 10 Dec 2024 16:06:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733846810; bh=IDAs66loD46ejrDZgcdhA2wj912kFUy5s0hoLSzyXSk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ADJHIkfiTV0YsOu/HXMzwiS2RxR+5D0cCrNlcj00SQU1YljAfFMCaXaJUWQ2rdFOU iSq4zLD9LGm3Rf1r52f2jsvLRxJzbx4RHtht+B0YxK/e+1a1h1XYL9yntzNDQfQiSZ Z5x1beU4WJoE/X7BOoMoY//o1542eZPoiKgXvjzBiFVv4Ok1RdB5kWh7b1KHLRwzuJ mITMmSURfkPXvsQi08gl0RbQOPq87tCYfo9u81kCz3a8Z/pS/rAzarx8y7plmv+tHv W3QP4/mwCMHdaVN4qnm8tdWHIryJnxDxcvzoT7KBq3kTjX98PcHL4zfil8uaKsh099 cHaTRkEQ4+Nsw== From: Arnd Bergmann To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, Arnd Bergmann , linux-mm@kvack.org, linux-rt-devel@lists.linux.dev, Ard Biesheuvel , Clark Williams , Jason Baron , Josh Poimboeuf , Linus Walleij , Mark Rutland , Matthew Wilcox , Peter Zijlstra , Russell King , Sebastian Andrzej Siewior , Steven Rostedt Subject: [PATCH 3/4] ARM: drop CONFIG_HIGHPTE support Date: Tue, 10 Dec 2024 17:05:55 +0100 Message-Id: <20241210160556.2341497-4-arnd@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20241210160556.2341497-1-arnd@kernel.org> References: <20241210160556.2341497-1-arnd@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 Acked-by: Linus Walleij Acked-by: Sebastian Andrzej Siewior --- 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. --- 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 4de4e5697bdf..e132effafd8b 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 && !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; } =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)) --=20 2.39.5