From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48BABC7EE30 for ; Wed, 25 Jun 2025 11:04:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A71FE8D0006; Wed, 25 Jun 2025 07:04:17 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9FA0C8D0001; Wed, 25 Jun 2025 07:04:17 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8C2FD8D0006; Wed, 25 Jun 2025 07:04:17 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 7690C8D0001 for ; Wed, 25 Jun 2025 07:04:17 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id EC4651204A8 for ; Wed, 25 Jun 2025 11:04:16 +0000 (UTC) X-FDA: 83593638912.23.2BDB55C Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf26.hostedemail.com (Postfix) with ESMTP id 2FD8C140008 for ; Wed, 25 Jun 2025 11:04:14 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=none; spf=pass (imf26.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1750849455; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fD7qqaRKnm3kYtFNKgvQ4Af/RMTJ9uqEnhnVg3rvJYQ=; b=yt7ljw73dtApnnTxuKjS7atM88quPFVcG9QLB2Z5CBJq0NdSAJJjVJrwPJHe0HWPSu3v8z LioPv9UM2cYUcclDvYe0R753ZZ8g+5TrjSieXq30U7MfJuont0wiP+wZBlEQMaHhgV48v0 PeT9z2tPuorwW/z9zpFdjoNDsjo7xiA= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1750849455; a=rsa-sha256; cv=none; b=xmMMUr6ZCWGVcyzRxIQ6dTrjVlRy4rz3rEa3ohUw7E1OiIlDLDLMPZrplRzciA3kgiPh7R SnyajtmTRMHAYMRirxK/7Nl1oQ9NrnWcYDLWWipp9ixA7lSEGxM11Hh90T/vVviEueFPKF rW8qHBp7j6w+8ssHtJ7AP+AJ+GoJwBo= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=none; spf=pass (imf26.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E40AB106F; Wed, 25 Jun 2025 04:03:55 -0700 (PDT) Received: from [10.57.84.221] (unknown [10.57.84.221]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DED9C3F58B; Wed, 25 Jun 2025 04:04:10 -0700 (PDT) Message-ID: <956f6ebe-606f-4575-a0a5-7841c95b5371@arm.com> Date: Wed, 25 Jun 2025 12:04:09 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/2] arm64: pageattr: Use pagewalk API to change memory permissions Content-Language: en-GB To: Mike Rapoport , Dev Jain Cc: akpm@linux-foundation.org, david@redhat.com, catalin.marinas@arm.com, will@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, suzuki.poulose@arm.com, steven.price@arm.com, gshan@redhat.com, linux-arm-kernel@lists.infradead.org, yang@os.amperecomputing.com, anshuman.khandual@arm.com References: <20250613134352.65994-1-dev.jain@arm.com> <20250613134352.65994-2-dev.jain@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 2FD8C140008 X-Stat-Signature: si449ajhwrefgspfjnbw6nsk1e9wr4cf X-Rspam-User: X-HE-Tag: 1750849454-996629 X-HE-Meta: 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 hf8+jaUY cbeB3BexS+6POesycjPEtExiRFCMez8I954hZoIRZHxk2vlPyv1VGu/JTDdb35gx1TRrq7nQ13VyxMpfJgWQO76zLqR4VsVWP4stcRUvotrbn+MTxlLeOTTuzvBrSXEYwWQIsN8yBKBUQrgyUQRD599CyqdEig67gsxr3WfKJa6nAbMk69c8TanPtig== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 15/06/2025 08:32, Mike Rapoport wrote: > On Fri, Jun 13, 2025 at 07:13:51PM +0530, Dev Jain wrote: >> -/* >> - * This function assumes that the range is mapped with PAGE_SIZE pages. >> - */ >> -static int __change_memory_common(unsigned long start, unsigned long size, >> +static int ___change_memory_common(unsigned long start, unsigned long size, >> pgprot_t set_mask, pgprot_t clear_mask) >> { >> struct page_change_data data; >> @@ -61,9 +140,28 @@ static int __change_memory_common(unsigned long start, unsigned long size, >> data.set_mask = set_mask; >> data.clear_mask = clear_mask; >> >> - ret = apply_to_page_range(&init_mm, start, size, change_page_range, >> - &data); >> + arch_enter_lazy_mmu_mode(); >> + >> + /* >> + * The caller must ensure that the range we are operating on does not >> + * partially overlap a block mapping. Any such case should either not >> + * exist, or must be eliminated by splitting the mapping - which for >> + * kernel mappings can be done only on BBML2 systems. >> + * >> + */ >> + ret = walk_kernel_page_table_range_lockless(start, start + size, >> + &pageattr_ops, NULL, &data); > > x86 has a cpa_lock for set_memory/set_direct_map to ensure that there's on > concurrency in kernel page table updates. I think arm64 has to have such > lock as well. We don't have a lock today, using apply_to_page_range(); we are expecting that the caller has exclusive ownership of the portion of virtual memory - i.e. the vmalloc region or linear map. So I don't think this patch changes that requirement? Where it does get a bit more hairy is when we introduce the support for splitting. In that case, 2 non-overlapping areas of virtual memory may share a large leaf mapping that needs to be split. But I've been discussing that with Yang Shi at [1] and I think we can handle that locklessly too. Perhaps I'm misunderstanding something? [1] https://lore.kernel.org/all/f036acea-1bd1-48a7-8600-75ddd504b8db@arm.com/ Thanks, Ryan > >> + arch_leave_lazy_mmu_mode(); >> + >> + return ret; >> +} >