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 3103955C1D5; Tue, 22 Sep 2026 15:37:42 +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=1790091464; cv=none; b=epzAVfxYyFNEiuP7ZTgVmtv96xyFAHDQcuzSBZLKno3FFd9hHTR/NZjN0Ud/fR1+mnieo0Zztd/skUKTw/i+uXXze+kD43JzhoshnZokcL2ukaOWOk8IdzF1RxwBRswiY4CWXtQ00bBB0DwfArNn1zmjXfb1iYT+2VIqLIMPeEk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790091464; c=relaxed/simple; bh=Ejk+F/Wux5yTvQzPF878nAZnzdraz7QYUlz/y227QJE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=aKTDlLRj6WJ168zhyn8jU+0CkTqHHPAhCi2EoIA/xVzgsS5a1k/Jo5W7CR9PqoSlZyVqF9AviDScWholowT3yzUcr/OxAv9XGfmGJIhd0ieWKMUuhYMDrYzHB0cQdt0JAzE2kw9ZnG9oSXv1sdip9+0jJ95Rx5412YxlhskSW6s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UNlcNUEG; 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="UNlcNUEG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6DA911F000FF; Tue, 22 Sep 2026 15:37:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790091462; bh=dWYqXXcVhqhum5QoL45NNyuXa4EfpjGCy/961eqdzvI=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=UNlcNUEGwtkyvsYR4zmSeGCvMkPLe+/ezusdX20O1bWYskX7cvdvIJuhhjuVtChmb L5+b54M4DXoNchVsv0nJ54pnhIsdEfA5oI47YpiDtjUztTpT4qzogzlKrUnLoaDon0 Hi/50oU8SeABFn/+BsGw1RL0cXsZ9uni0c7ibjurbKnftlBLuqaA2M5V5zWFn9PE1b n2j5Mady9bfFc8fKJ22XaOT4EwjJPIZOiQbv+8Od9Wmuwkvc0lPJh+Kjy/qRzctIDv BhT9VIJmX/JVBTgDo4khmxS4qLbtj4ncYW3ywiP/LSPDFHak7FA0nynQk8qUTpmRo7 4FhJkMkThxUjw== From: "Lorenzo Stoakes (ARM)" Date: Tue, 22 Sep 2026 16:35:34 +0100 Subject: [PATCH v4 03/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for MMU riscv Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260922-rcu-pagetable-freeing-v4-3-fe1ad1f1e303@kernel.org> References: <20260922-rcu-pagetable-freeing-v4-0-fe1ad1f1e303@kernel.org> In-Reply-To: <20260922-rcu-pagetable-freeing-v4-0-fe1ad1f1e303@kernel.org> To: Andrew Morton , David Hildenbrand , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Guo Ren , Brian Cain , Geert Uytterhoeven , Dinh Nguyen , Simon Schuster , Jonas Bonn , Stefan Kristiansson , Stafford Horne , Rich Felker , John Paul Adrian Glaubitz , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Russell King , Vineet Gupta , Michal Simek , Chris Zankel , Max Filippov , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , "David S. Miller" , Andreas Larsson , Richard Henderson , Matt Turner , Magnus Lindholm , Catalin Marinas , Mark Rutland , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Madhavan Srinivasan , Michael Ellerman , "Christophe Leroy (CS GROUP)" , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Richard Weinberger , Anton Ivanov , Johannes Berg , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Arnd Bergmann , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jason Gunthorpe , John Hubbard , Peter Xu , Yoshinori Sato , Shakeel Butt , Jonathan Corbet , Randy Dunlap Cc: 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, Hugh Dickins , Qi Zheng , linux-doc@vger.kernel.org, "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=1601; i=ljs@kernel.org; h=from:subject:message-id; bh=Ejk+F/Wux5yTvQzPF878nAZnzdraz7QYUlz/y227QJE=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLI2LchuC1lS+yl/saWZ4KXsS/+f/mMRKmHc9UBbod6B2 YU98CxHRykLgxgXg6yYIsvzL+L7g0TC5nVe8HeDmcPKBDKEgYtTACYiP5Phv+8ioR33clR2yb5m l1T66KMtEtO5qfBsf+mk6EU66XL/njAy7OdZ56cxmWV7qvxM/cnbUvUPnrh05fThTHmL9/6/nNY oMgEA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 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) --- arch/riscv/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 505eed4af932..3529ed1861ce 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -208,7 +208,7 @@ config RISCV select IRQ_FORCED_THREADING select KASAN_VMALLOC if KASAN select LOCK_MM_AND_FIND_VMA - select MMU_GATHER_RCU_TABLE_FREE if SMP && MMU + select MMU_GATHER_RCU_TABLE_FREE if MMU select MODULES_USE_ELF_RELA if MODULES select OF select OF_EARLY_FLATTREE -- 2.55.0