From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 2B94E46D09D for ; Mon, 7 Sep 2026 11:18:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788779932; cv=none; b=inPpOtWuWYOtMpUX1hdP9oEwz8xpSmhD5OhdPmbMS3np0SYTE3XIxGpnQwX3AABsQ3meMp03mZzph9iKKgA+ZMoPq8e0mgOX2ggpEMJMdl1ay8Jj6ObA9KI8GaoRARZhKZCbys5IYMZsNQvemXUMxaUSh6h7H1O0T9FctVM7IE4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788779932; c=relaxed/simple; bh=nRbZdy+9771v+FTfrzh4Uias0U1VEfTEVi8wbC862Ao=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=eJnI1pOVDWBr7NZQCGj9PaHAsLLSQTch1XYtWe288+FeqMRXBQ1TnMagykqkoyCURtRdnQDzX+vBY/Z0LRhnbqZnfuyL/h+2U7EX0ZeOIcQwcl47xKaZD7xMB0VvcjQsnV8HvJEHwa/sEGHFN4rq4qGbwSUmh5LufcuxgKqOlEU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=F8m423Lh; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="F8m423Lh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D51B1F00A3A; Mon, 7 Sep 2026 11:18:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788779930; bh=6Z/SgvhpSWZZrEnPffWXml8Hd3wiK1YMY4/p+rNNK8Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=F8m423LhiG/t/9Wa6UuLgMPisSPSaM0ws6sLzcdYwfW2FEYdK/K+Z5A9zDpAI0e7z 7zcW1KROfscWEZhgA/J8JMfiW9sSjf23XIOE1DtFpqV6RhSBlXktdEsVQQTJgaOMM4 U+NDNAEYwpedUUzpWNcWoZO3jLmIdBS4eK85R8SBGtCl4vMw4N9c0Nuc0u/AMBroJV oRiUG+v7J4tZ82zGGs47AX3GVu31zIt3DwoR5PgXBUt3YEZASX0JDS1IsnET4tQ56d O1HMQB9Is+Yp9B8WSFxR5SaTnXfE7G6ZgJ+Now4boANlh1gpw9obeOJHtK/TEdEkGs kj3KDL5gjdRFA== Message-ID: <69db9546-d14d-4107-96b7-30963292c2bd@kernel.org> Date: Mon, 7 Sep 2026 13:18:42 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 1/3] mm: make persistent huge zero folio read-only To: Mike Rapoport , Xueyuan Chen Cc: akpm@linux-foundation.org, ljs@kernel.org, usama.arif@linux.dev, ziy@nvidia.com, baolin.wang@linux.alibaba.com, liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, kas@kernel.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, luto@kernel.org, peterz@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260901151818.3191443-1-xueyuan.chen21@gmail.com> <20260901151818.3191443-2-xueyuan.chen21@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 9/7/26 08:03, Mike Rapoport wrote: > Hi Xueyuan, > > On Mon, Sep 07, 2026 at 09:11:14AM +0800, Xueyuan Chen wrote: >> On Sun, Sep 6, 2026 at 6:00 PM Mike Rapoport wrote: >>> >>> >>> I believe this is an historical artifact. change_memory_common() already >>> updates the linear map when a vmalloc mapping switches to RO and the system >>> supports it. >> >> On x86, set_memory_ro() does work on direct-map addresses. >> >>> >>> I believe arm64::set_memory_ro() can change the linear map in the general >>> case as well as long as can_set_direct_map() is true. >>> >> >> On arm64, I'm reading arch/arm64/mm/pageattr.c, and the linear-map >> update in change_memory_common() is only reachable for vmalloc >> addresses: >> >> set_memory_ro >> change_memory_common >> area = find_vm_area((void *)addr); >> if (!area || ...) >> return -EINVAL; >> >> So set_memory_ro() on a linear-map address returns -EINVAL on arm64. > > And I believe this is an historical artifact rather than necessity. For > configurations that allow set_direct_map on arm64, change_memory_common can > update direct map too, it just need to be implemented there. > Are we sure the other architectures do what we want in their set_memory_ro? Having a dedicated set_direct_map_ro() with clear (documented ;)) semantics does not sound too crazy to me. -- Cheers, David