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 CCA1E55C1C2; Tue, 22 Sep 2026 15:38:04 +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=1790091486; cv=none; b=TcV60232nidtwsCDEpWRakkjye7WTNz3ekN+m4ZSBSzIQdbPWsYHN9YBw+PuA3X2Tb1t5XEGPZ4gPoyanrLyhJ9CVPUSU8wl+xae0rup9QQXtYT/Nm3TeMBlWdj5YgaQwZVFtEhzMEaEGSeLauxWmDV6tmRuRw7RYleVETDxfUc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790091486; c=relaxed/simple; bh=DfBAaXdC7t7vNoXwDFH4KxY7MB20la/qqFRKCtU73zE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=jHQqV644E2haJeiZRhMC90KRzAL2JALLSkiXaDD2J59yeVmZRnjdSpfHgeGnRffpY37b5gjSetzT1244tlsFZ7C74iloKXEFw6d8eYCL3K9zQq19NaIP/liZi9Ip3tbngVN08upQNtXdP936YRP8N/O5+NfPoHs5Wtk9qTq2jlk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=baLVS6KH; 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="baLVS6KH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4F1AD1F00893; Tue, 22 Sep 2026 15:37:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790091484; bh=3qIS4A8O4N5dYDsCKKL4hiQNRSaqHHy/s6/A7yaKLWg=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=baLVS6KH22XEePkcCK/XQL5WUTQhEfQO+oVeyTZCmHU5hvgW/sC6ri+yz+fZAEvUu 4AB4f9B49fUmMJLa00WCl/Lq29SV/3o2xefFCut0zjtkzvHJxT2gLbBl6t/7FWSah2 cSFBx9oSTs3cHExoGi7w0wc7bej6do9PXjbWtdyMa5VjjS6sF0POU26Vm/6/jtKgE2 NUet2CcbMqFq9W3zLDl2+ZbTlY14Hv3I9LNx4pdfIGzHNrM7J3UDOAF8heZnHAptmF QbMCEdCV0Sqooq2HWiC0wBKEP4F5ZEAKre1J+LA0yZT213KYQ7ZAoYR+7OowJbWVy/ GA+TVgecxHh8Q== From: "Lorenzo Stoakes (ARM)" Date: Tue, 22 Sep 2026 16:35:35 +0100 Subject: [PATCH v4 04/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for MMU arm 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-v4-4-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=1983; i=ljs@kernel.org; h=from:subject:message-id; bh=DfBAaXdC7t7vNoXwDFH4KxY7MB20la/qqFRKCtU73zE=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLI2LcgWNO2ZyhxnUcn2yn+6ab7p3uPZ3pZnN3/ZwLHOx /+0md2JjlIWBjEuBlkxRZbnX8T3B4mEzeu84O8GM4eVCWQIAxenAEzkeT7D/5S0tP6NOvsf9/jM NlwxdcVR6zZvveSOBtuop/zxvYaTGhn+KX384XMub+sLLqYbIeFdF9Ts3numFxt4mpcFR7aFZ6x gBgA= X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Commit a0ad5496b2b3 ("arm: mm: enable HAVE_RCU_TABLE_FREE logic") enabled CONFIG_MMU_GATHER_RCU_TABLE_FREE (then named HAVE_RCU_TABLE_FREE) for SMP arm architectures with LPAE enabled. Regardless of whether CONFIG_ARM_LPAE is enabled or not, the same page table freeing functions __pte_free_tlb() and __pmd_free_tlb() are used. Non-LPAE PMD page tables are folded into the PGD and freed by pgd_free() (PGD freeing is not part of mmu_gather page table freeing in any case), so this is a noop in this case. Since commit 358d1c39c82a ("arm: convert various functions to use ptdescs") both LPAE and non-LPAE PTE page table freeing uses tlb_remove_ptdesc(). Thus all page table freeing is performed under RCU with CONFIG_MMU_GATHER_RCU_TABLE_FREE enabled for LPAE and non-LPAE and thus it need not be gated on LPAE. A UP arm system can set CONFIG_PREEMPT_RCU, so a future pure RCU page table walker requires MMU_GATHER_RCU_TABLE_FREE to be enabled on UP as well, even if concurrent GUP fast is not possible there. Therefore, it is both safe and desirable to set CONFIG_MMU_GATHER_RCU_TABLE_FREE for all MMU arm architectures (nommu does not perform mmu_gather operations). 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/arm/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 408aa58a2a5b..72b9afc6ae10 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -134,7 +134,7 @@ config ARM select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP select HAVE_POSIX_CPU_TIMERS_TASK_WORK - select MMU_GATHER_RCU_TABLE_FREE if SMP && ARM_LPAE + select MMU_GATHER_RCU_TABLE_FREE if MMU select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RSEQ select HAVE_RUST if CPU_LITTLE_ENDIAN && CPU_32v7 && !KASAN -- 2.55.0