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Wed, 23 Sep 2026 07:18:38 +0000 X-Mizu-Trace-ID: a804e1edd13ff3f4 X-Migadu-Flow: FLOW_OUT Message-ID: <8769d7a8-9442-4dbb-9828-01447e4320d1@linux.dev> Date: Wed, 23 Sep 2026 15:17:56 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 03/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for MMU riscv To: "Lorenzo Stoakes (ARM)" 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 References: <20260922-rcu-pagetable-freeing-v4-3-fe1ad1f1e303@kernel.org> <20260923061551.84398-1-lance.yang@linux.dev> Content-Language: en-US From: Lance Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 094ED40002 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: fiuwd48r7bwhh847wnwkosow5fwerdph X-HE-Tag: 1790147920-167493 X-HE-Meta: U2FsdGVkX1/AOFJRSxZnpk7AQzNVP9ppuAPzIvO0as5kFKIaQ9NarPASfe/xkbLwdAcb5mZzhpwybZvoeyh8vuBN0FFr7N9dCNWu6KBXvGkq5ST6QTlLf8YcQKvGioN/9GVn/ObDvNZYVW2A13rO0UbchHGDqzRvM33sTWEk6XhbsGEZdLi5WCh/iMaR6NVAF1VWa+2HPJRHcegkE4CvQY5aVdDXNaijIk6JZkfAdNkCJ0J2xiFrS/sBRADVYsacZrH3yyJ9NHKF/8nUnn0Fj9hDqRBheFaYl3waOEEcv2R/OhDeQBBKwMfl2xmB0AVkUt7OvvoE1V72FKbjnZHdSdpAACqn/KLz7h8NjtqqQVnXfmamTgv9GRMb+LEUY+NGJtZgga/AUPkhrNCSzP50ylUGcLeXJSK6Hz7ioqURH7QkTdjobrkenI6dL8Ouaqvasi9hpTq9FelQtJXgMNiyXj9FCbPU52FwgHud77s6rYAo5sA9FNDN1c5znu5ouJ8wLJl/lKSgUWSrG3WiN5KiXPVfTUeS7LqRrspW8FLXUXTagV8vwPBfZPgQobvaSEu0aSRAk+jBwDCP/NqUYPDQH8wQUCEFMVDPHWN1Vfkd/YEXrtwta0tpNuHAUnVAaqyiYzCjS841pSP95zkZwlcZnNiPs4JsKEA6Yl/rofwd/Ah1NQF1jvW7JHMKU2LbzkzHjBwUU4j/qv+vTxUKxyPFZCQdHhv2Pl5jGC9aEDWXlS5ctt2qqXJ3AQjqGQS9XGzSzt4dDhXuPF4REawnAvOqO2pPqc9YyyIl52ukXOaga3Wr6uwJknZLzOmuC555ybmwSqPr7sabwK5SnieJbVwzEyKq3AqwkBNHUh/2hq50XetUDxONpzzSkh5n8wMnIFll1grBHn9J7KpMbSQqMFqJg88WRyM/p0t5GA9buc7wIz37aRm4RTsYPEOL8Zb+tfMUWBKXnkoThsWKAKJ1dhx ZVe45EHW XdGBewdsdvXMco0zc+26OQBbVdrNlQbrKropOSLLLZTC3RtkYWxp7kxOHpABJXGx8qR4D3xmk/ByhVV3JCvNhoYbTh9Z3t82qAtRXhlaPULhmoHxBHAqh9RunRCP8htTkiz0co57hM1RuA/RGv2ltv28K40rnfmoAPAh/ne/ZEfEx2fnL9IyyljW+WHQgJPQjkGIKrdTsG+0PksfgbcxIBrllb8k+uvN0x2BIYXEWtH5Uv4WafAk/WpLyDF3MzGdtp4431kDjGrwCRxJnh2E/5dVIdcMynOBm5Km77ohxbrjJsnyTqsWo7zg0ATGAcsftM8pOTsM6bWHBsntdwRSpzx1P9EZZ7ZqxDN6fUGcN283G7lK5EvwdrqbxSCP7nncCSvxqfy0weGiAjPv2pUFMaUSixbUq7rxRUXYicv78wXpmBN9ecbEMkRx2GRN34B+qSRvrziZ/R4xrgMA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/9/23 15:05, Lorenzo Stoakes (ARM) wrote: > 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! :) Cheers! > A cheeky A-b tag possible too? :P Sure thing! Here it is :D Acked-by: Lance Yang