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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 39526C98308 for ; Wed, 23 Sep 2026 07:05:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 275F56B0093; Wed, 23 Sep 2026 03:05:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 24D9A6B0096; Wed, 23 Sep 2026 03:05:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 13CE96B0098; Wed, 23 Sep 2026 03:05:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id EB5ED6B0093 for ; Wed, 23 Sep 2026 03:05:47 -0400 (EDT) Received: from smtpin15.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 767A2C067C for ; Wed, 23 Sep 2026 07:05:47 +0000 (UTC) X-FDA: 85244141934.15.6B4867F Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf01.hostedemail.com (Postfix) with ESMTP id C87854000D for ; Wed, 23 Sep 2026 07:05:45 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=EAnwJUiA; spf=pass (imf01.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1790147145; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=WmR3kOZB3ACXfNo3laV3NfaLUopFF9HlVbP149Haq1Y=; b=hl6L2j7P2Y35jHUHQzuNvejKeGFtwccKjXCWzhVQIzZ5yHzJ0/J6fPZ88WQtQJCcpWM3GA QWsE5eYjm27qj/e05hH1F6f0HhUpoderssLFzVza7ea4M4obilVnSvf3CnwKlCRZRXGLUv bXEeKua5XwJcNnwR+UiUwHyfVoE3908= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=EAnwJUiA; spf=pass (imf01.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790147145; b=DsVsNJwZyi9B+IT9Se2ffgiXy7sIYd/KMf6sbr0kAt6wc0cw/QI0Ay9Su87bqd7qar4W+w 8MzgKsVpVTvX5FtD8Mgyxtb+74AZcmmWI6YTSdGNFMIXHi5rEYAcNoqx/nv6byTgMBLjHu YXTvpRrejLOEb6xprmJTUaB5UfZFi+o= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 0B240436CF; Wed, 23 Sep 2026 07:05:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 321A21F000FF; Wed, 23 Sep 2026 07:05:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790147144; bh=WmR3kOZB3ACXfNo3laV3NfaLUopFF9HlVbP149Haq1Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=EAnwJUiAqyojRKJf9KNQTwXny7L+XnGgJ0trGGXwGUbbfY4A9uWcu9K0SsUiWOgmc yb41CHhlT/HBuBnzVyYR5/fQuSR3XjSBl9uXtd/UfutbvMg5gyAst3woO5CUYyXhGy AD976W51iwZLDg5mT7WlRmgWnW6l1yj7+OPvlJqhBDwYsyITZldKacOLPw8X3r5iwh xdzP0DsHgF0BxH20eqFZEB0DFdFfRS+stF04cj498KEixAmiiwoIiMX7fOO4v2ki3T qJvjlyssz0DhAO2ce9/8NcZk01mVg0oHHUpA2uecyxQvoQ0UuWqDvbZALG/EIOlt5M hZKVkk39Tca+Q== Date: Wed, 23 Sep 2026 08:05:21 +0100 From: "Lorenzo Stoakes (ARM)" To: Lance Yang Cc: akpm@linux-foundation.org, david@kernel.org, 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, usama.arif@linux.dev, kas@kernel.org, guoren@kernel.org, bcain@kernel.org, geert@linux-m68k.org, dinguyen@kernel.org, schuster.simon@siemens-energy.com, jonas@southpole.se, stefan.kristiansson@saunalahti.fi, shorne@gmail.com, dalias@libc.org, glaubitz@physik.fu-berlin.de, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, linux@armlinux.org.uk, vgupta@kernel.org, monstr@monstr.eu, chris@zankel.net, jcmvbkbc@gmail.com, will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, peterz@infradead.org, davem@davemloft.net, andreas@gaisler.com, richard.henderson@linaro.org, mattst88@gmail.com, linmag7@gmail.com, catalin.marinas@arm.com, mark.rutland@arm.com, chenhuacai@kernel.org, kernel@xen0n.name, tsbogend@alpha.franken.de, James.Bottomley@hansenpartnership.com, deller@gmx.de, maddy@linux.ibm.com, mpe@ellerman.id.au, chleroy@kernel.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, richard@nod.at, anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, arnd@arndb.de, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jgg@ziepe.ca, jhubbard@nvidia.com, peterx@redhat.com, ysato@users.sourceforge.jp, shakeel.butt@linux.dev, corbet@lwn.net, rdunlap@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, linux-sh@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-snps-arc@lists.infradead.org, linux-arch@vger.kernel.org, sparclinux@vger.kernel.org, linux-alpha@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-um@lists.infradead.org, hughd@google.com, qi.zheng@linux.dev, linux-doc@vger.kernel.org Subject: Re: [PATCH v4 03/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for MMU riscv Message-ID: References: <20260922-rcu-pagetable-freeing-v4-3-fe1ad1f1e303@kernel.org> <20260923061551.84398-1-lance.yang@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260923061551.84398-1-lance.yang@linux.dev> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: C87854000D X-Stat-Signature: 3suaefxzr8ehknp51u9rpju7duazoag3 X-Rspam-User: X-HE-Tag: 1790147145-280616 X-HE-Meta: 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 LcRz4pFV ZolZOj5aiAs4llY1vGpqfdRYBvv26i3naoUCkgMsvcDKbFL9JcdFeeppup7pgJFXuFlPwGFiJESIIdDEEsUURFhMRExWxpu9O+nIrki2uUj8ELDnRZ/e78J6JObiq2uBekxtMZp/TNSANYIIXuY8/YgNoyraEJkwzBiALnHthfEdN6HxfWpXa4HLS5ko036Ef6ow7GTA+RJGlrkfBr0PDI8hDm6ffjgMZTgGaTsVmCY4XAJ5Iibp6W4AMVhZ3GNwoaeaJE469ma1Dyq9Trtz3TAMFNrGV8y7kZ0/UxXFnJsnSK7fhQ5cxIdOjeoKKfFjQXeEdisp104hCwXYBcOHr8Za1INJqnJkb6CZyLvTuX8BAdANf/FP6rVcKRim869gupxpRggWzqiXydIE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 23, 2026 at 02:15:51PM +0800, Lance Yang wrote: > > On Tue, Sep 22, 2026 at 04:35:34PM +0100, Lorenzo Stoakes (ARM) wrote: > >Currently riscv gates MMU_GATHER_RCU_TABLE_FREE on CONFIG_SMP and > >CONFIG_MMU. > > > >Commit 69be3fb111e7 ("riscv: enable MMU_GATHER_RCU_TABLE_FREE for SMP && > >MMU") enabled CONFIG_MMU_GATHER_RCU_TABLE_FREE for CONFIG_SMP, CONFIG_MMU > >riscv builds. > > > >This is expressly for the safety of GUP-fast walkers (CONFIG_HAVE_GUP_FAST > >is enabled if CONFIG_MMU is enabled). > > > >Naturally a single core system does not encounter issues with software page > >table walkers being correctly synchronised across cores, as there is only a > >single core. > > > >However, CONFIG_PREEMPT_RCU is still available on a riscv UP system, so for > >a future RCU-only page table walker, this guarantee is required to prevent > >concurrent page table teardown. > > > >All page table freeing is already done via tlb_remove_ptdesc() so the > >conditions of CONFIG_MMU_GATHER_RCU_TABLE_FREE are already met. > > > >This forms part of an overall effort to switch every architecture to this > >mode. > > > >Acked-by: Kiryl Shutsemau (Meta) > >Signed-off-by: Lorenzo Stoakes (ARM) > >--- > > Yeah, for RISC-V, page-table freeing already goes through > tlb_remove_ptdesc() :) Tested on QEMU, no issues seen :) > > Tested-by: Lance Yang Thanks! :) A cheeky A-b tag possible too? :P -- Cheers, Lorenzo