From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794595320; b=Q1P2A/o1TsSG4x5lNTfqJAGV1PoBFNMYZ3UphwGj+i/ffVBKPZ8ElrWUb8Grz+/LYCCQ vTbKxk2eR4XkwcmfAnjjmmiucGzZgyir+OXApeNmx0gFeFPvSwp6T/Y5z91T2r8I4Wsuj 01JjaF5ejDe4xz3zWBbOxzscl0OEtMi05k72h+Q4dqsVn7yxkTjoxfupznhoacozSgECM lTuixg+WjoWbllnZ4D0c4jopYGtHWCvBwSAtMxdqmylmJk2dHPi7/7Y+ULDkcj6mpXY1V ip/YqqY3iASfG/yNGznsLncEO/5knh4L12rWgHw/RCaHfi6lXi8CRyBqRR946WLecuA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794595320; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=VytgQi4p8wcmmELrEfY15mVmpLYzi4XAlS7bqFMpaOA=; b=o722jlAENY61mM9P4BFITebrL+JZMqWlWqgIuCEwwqdzLBdAgEp5w0emgamRvRrfyHJG DWdn6Hw+i+R3jaKZYHx1upTvhy2jXRv/fYI3MUzQZt4uH/9ldHo4YTqIFrdQzAHzPIyx9 Qa8qejfC6GeMjc3TC5ShvPqTGqjjX+Rv9Oj41kY9mzfG/hpaE9VVq6j5DsPFeQgGuNCpn Xyc67olA9N2p/jmVeRN9+38jvq/MHN7ruv0DR1+ktcvujQ0CPwwtKEpdYSQx/UiCv3vPY Im0Gcfee+82Aa7ZcZhonqW9sscDy3ZQobtzwYISif5P7sJMgvdDU4CasvUpLUAI4x2Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="cfI/L2eY"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E5D6F606A330 for ; Fri, 13 Nov 2026 18:41:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=cfI/L2eY Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7E0221F000C4; Fri, 13 Nov 2026 18:41:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794595319; bh=VytgQi4p8wcmmELrEfY15mVmpLYzi4XAlS7bqFMpaOA=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=cfI/L2eY2qjwVL7APHC67QJOIGk/JNOUabcKBMNTHVN19Rcz72eUV6Yh3y5Ea/LHZ z5QbQ0lofex0YKPkP/CrCot0WtLB3Iun9cb9TpGzWGq7i0diBi7RiTfH+PMAtEzL2+ C0j/tS7srsbkDAQQkLK7ashTa4LxtBlawzOcVQduTw15A7JC0FoBx70BE+lVHeY9Dq c07fq9ZOjzPKmREqLefO5blbiTlVapyN80u0xRg/xm4Y01ZY7klw7sdg1ydyXEPskb 46DP+YMZNRJ2jvH8liJQifBhGUdO/X8ERo88dTaNWRmserH3XKGKSg7PzJ1GdT/0k3 sU3CZpk80JuTg== Date: Fri, 13 Nov 2026 18:41:52 +0000 From: "Lorenzo Stoakes (ARM)" 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 , 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-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261112112528.1116405-4-arnd@kernel.org> 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 With Mike's change applied, LGTM and: Acked-by: Lorenzo Stoakes (ARM) > --- > 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)) > -- > 2.53.0 > -- Cheers, Lorenzo