From nobody Sat Sep 26 13:09:29 2026 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 246CB47B437; Tue, 1 Sep 2026 11:05:26 +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=1788260728; cv=none; b=tUBjPnJzOqSxrOVCGnWd3DGe00wCYFERsRcdbt3M2F9Pc8CFVdlPgw1TaafEOFKZGOIVwTPQmWPNgagMAwgQFvCJGyiXcPFlLR6m3J+7WQzIkWz4kg+1Gob4uzlyGIXDCQqd1jdiKvsAoWIVQsENaU3/OttMS7GAIIl2vlKprys= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788260728; c=relaxed/simple; bh=QsmXD4bhTqKAKkUCvIrmgq1QZ07I5df5Am7bAMtZYGk=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=lOQqVtoEcprtopMvYu+HEm8DjTPchO/Ra9glyK5qFgwCBZ1PdNCnjFrD/uAp58z58G8tuG69DyQbih8gdDygKg/tj0HkXqnchh9Iav9sjZr+lGG4joFnxj2DBB1Nv9hsqAZL5k0ATj+O77QYlZxDFo2rmUAngbWcz8VURUcMxBE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oC+PeNze; 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="oC+PeNze" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A7C5E1F00A3D; Tue, 1 Sep 2026 11:05:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788260726; bh=qrlRHDKkKksSse2z7V875Db2PCZ3B/h/JK+Hse17ruk=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=oC+PeNzeXGgygw1GLni0qWUre/UeVngidRRvYApKsIuI5ZQ9UE2DPzmFOWAvU+g+K Tq/3aDUz7ili/2efyU4PlHqc4GfIWiSDKgHgH3le8IEHHhoy/DUc38Lc+0WQpCeGPG rW1c4ZG9bfi4OATQ6DHNR0fyXdkxqGq3QPbClHaCIRwWu+ABXEXLLxICfHrWXARDtb +LUmHZFDUfMdtRqvbUudVUpWM9JR7VimV6S8ZL7eqX/eWlR187yhtTkD07XSGcPsWy gcqOqwvTpNr8iG4jYGW5qsgXdCFo+r0wg0Wc5KcSpJcv5vsQMVQF/SGuJxP5ELbZHT 7A80AG8ayckPQ== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 12:01:21 +0100 Subject: [PATCH 01/12] mm/huge_memory: zap deposited page tables after an RCU grace period 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: quoted-printable Message-Id: <20260901-rcu-pagetable-freeing-v1-1-5456a81c8212@kernel.org> References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> In-Reply-To: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@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 , Yoshinori Sato , 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 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 , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=1907; i=ljs@kernel.org; h=from:subject:message-id; bh=QsmXD4bhTqKAKkUCvIrmgq1QZ07I5df5Am7bAMtZYGk=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmbXR/NqX0p/yX2JqF0V1HnP3EWDwWHnX5NpPjjHPWl V9mHyu7O0pZGMS4GGTFFFmefxHfHyQSNq/zgr8bzBxWJpAhDFycAjCR5pMMf4W3zTCOEpo4p0nf ZKn7zKK0mwzx203Lmh+2vpCbIlL5eiUjQ5vI2p2Ln6522hS/bpW4K6e0j0lI49S9FarGj/2PeQg u5AUA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 When an anonymous mapping is collapsed for THP, a PTE page table is 'deposited' with the installed PMD entry. This is done in order that a split can be performed without needing to allocate additional memory. The freeing occurs in zap_deposited_table() and is done directly without any delay via pte_free(). This is currently not a problem as existing page table walks are protected by the mmap or anon rmap lock. However this becomes problematic in a future where RCU-only page table walkers exist, as there is nothing to prevent a page table walker that started the walk prior to collapse having its PTE table freed underneath it. Commit 13cf577e6b66 ("mm/pgtable: add pte_free_defer() for pgtable as page") already provides us the mechanism by which to solve this - pte_free_defer(). Therefore, as a prerequisite to a future commit which will permit fully RCU page table walks, update zap_deposited_table() to use pte_free_defer() rather than pte_free(). Note that the IPI sync in collapse_huge_page() is still required to ensure refcount correctness against a GUP-fast operation. This is because GUP-fast might increment refcount, but __collapse_huge_page_isolate() determines whether it is safe to proceed by checking folio_ref_count() against folio_expected_ref_count(), so the two must be mutually excluded. Signed-off-by: Lorenzo Stoakes (ARM) --- mm/huge_memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 54494c3fa983..505f7b62ff28 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2476,7 +2476,7 @@ static inline void zap_deposited_table(struct mm_stru= ct *mm, pmd_t *pmd) pgtable_t pgtable; =20 pgtable =3D pgtable_trans_huge_withdraw(mm, pmd); - pte_free(mm, pgtable); + pte_free_defer(mm, pgtable); mm_dec_nr_ptes(mm); } =20 --=20 2.55.0 From nobody Sat Sep 26 13:09:29 2026 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 8D2033812C7; Tue, 1 Sep 2026 11:05:42 +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=1788260743; cv=none; b=hQZvOyxMM+/pgMI4wbXckeJExWiEzGzukVkgXY+vWXDg7RFnNXDUTyvj6KZW25rR45OGeQxnxnmiUye6jGptbRgliXMntTmO+xpJm1iwAsDuOOygix4JIVRfy9fXAUcASJRfQ6l3dPk0u+0AwZYIqTb6228/gZhSEfDqp8FDphA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788260743; c=relaxed/simple; bh=yQUOoL+4VfJjLW5MASkaQAQ+ZTfTJR7/6HJ0TBTi3s0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=A3jDKqj/5KLKTSKmGxiX+7vidxOv2VSy+f4Ps1Rq6PakC9RpU6Z3tSR+woKyra/pAvr2erQxWz3oKLo5r8AP+KSITIF8IU6ocO02QjhfO3QPnBmc07ldOpw9JQiDZZ490ITSDAUGw/5ywRrVIMwgQaVnP3+vFmrqIAB8vWXBuE0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=L3y3kV7x; 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="L3y3kV7x" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1C2071F00A3E; Tue, 1 Sep 2026 11:05:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788260742; bh=hla1P//jUaEzl3P+0ure5xER+YPzVxn4O3sMhLZO6MY=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=L3y3kV7xP4GUQ6JyAP1rkMfIJXYsMZuVy5QNWrVPBCCzYr1m/zRVW74DSR8ResTEo WECSOQnrU2KwpiuxpnTE1UA4d0FuoyXQN0d9YE8EolumEfUnyTDwNtfcIDlVt7KloM Stb30O4xGLB71yHukiz+OKGtLc6cEZomjcvLv5MGQtofBh9wawUjL0jBb3Msd7sAAZ UQV3deK3RVrSb71bdlxmKN+UU8YmueQsNT1pLtnZXPue42MCyLg+NcShK8lTEjZWG1 n1ra/YYdx3fQ7xc+3cCJ2jrd3TuuBiCegbd5mwrOkD16uT7hXFpLqmM3fEm53lwmes 8rubg+iwF6wZw== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 12:01:22 +0100 Subject: [PATCH 02/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for most 2-level architectures 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: quoted-printable Message-Id: <20260901-rcu-pagetable-freeing-v1-2-5456a81c8212@kernel.org> References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> In-Reply-To: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@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 , Yoshinori Sato , 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 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 , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=3562; i=ljs@kernel.org; h=from:subject:message-id; bh=yQUOoL+4VfJjLW5MASkaQAQ+ZTfTJR7/6HJ0TBTi3s0=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmbXQPXtAV0qUlJhy9XffShy3TVrz3O6nqNue9t23Bu r/Of/03dJSyMIhxMciKKbI8/yK+P0gkbF7nBX83mDmsTCBDGLg4BWAiOzMZ/vBU++3nub25tjfv Qf2t/WUP0zW8N+9MaBTdWsl+irnghQEjw/S+adZz8t7f50p6sVxQLcWQN5PVj/VIc+/dA5+L/rS GsAIA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Commit e3ecf7c7d082 ("mm: pgtable: convert some architectures to use tlb_remove_ptdesc()") updated a number of architectures from using pagetable_dtor() + tlb_remove_page_ptdesc() to using tlb_remove_ptdesc() in __pte_free_tlb(). This is meaningful as tlb_remove_ptdesc() allows for RCU page table freeing if CONFIG_MMU_GATHER_RCU_TABLE_FREE is specified. The csky, hexagon, nios2, openrisc, sh (except X2) and m68k-sun3 architectures all have 2 levels of page tables, so the only page tables ever freed by mmu_gather are PTEs, so this update suffices to ensure that every page table freed by the mmu_gather mechanism is freed under RCU. Therefore, update all of these architectures to select CONFIG_MMU_GATHER_RCU_TABLE_FREE. This forms part of an overall effort to switch every architecture to this mode. Signed-off-by: Lorenzo Stoakes (ARM) --- arch/csky/Kconfig | 1 + arch/hexagon/Kconfig | 1 + arch/m68k/Kconfig | 1 + arch/nios2/Kconfig | 1 + arch/openrisc/Kconfig | 1 + arch/sh/Kconfig | 1 + 6 files changed, 6 insertions(+) diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig index 4331313a42ff..80f89ef1d962 100644 --- a/arch/csky/Kconfig +++ b/arch/csky/Kconfig @@ -96,6 +96,7 @@ config CSKY select HAVE_SYSCALL_TRACEPOINTS select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU select LOCK_MM_AND_FIND_VMA + select MMU_GATHER_RCU_TABLE_FREE select MAY_HAVE_SPARSE_IRQ select MODULES_USE_ELF_RELA if MODULES select OF diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig index b48491140013..d9b3fb86556b 100644 --- a/arch/hexagon/Kconfig +++ b/arch/hexagon/Kconfig @@ -23,6 +23,7 @@ config HEXAGON # select HAVE_CLK select GENERIC_ATOMIC64 select HAVE_PERF_EVENTS + select MMU_GATHER_RCU_TABLE_FREE # GENERIC_ALLOCATOR is used by dma_alloc_coherent() select GENERIC_ALLOCATOR select GENERIC_IRQ_PROBE diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig index 11835eb59d94..e29610fd1240 100644 --- a/arch/m68k/Kconfig +++ b/arch/m68k/Kconfig @@ -36,6 +36,7 @@ config M68K select HAVE_MOD_ARCH_SPECIFIC select HAVE_UID16 select MMU_GATHER_NO_RANGE if MMU + select MMU_GATHER_RCU_TABLE_FREE if MMU && SUN3 select MODULES_USE_ELF_REL select MODULES_USE_ELF_RELA select NO_DMA if !MMU && !COLDFIRE diff --git a/arch/nios2/Kconfig b/arch/nios2/Kconfig index 9c0e6eaeb005..b0ccfc3b7a7e 100644 --- a/arch/nios2/Kconfig +++ b/arch/nios2/Kconfig @@ -19,6 +19,7 @@ config NIOS2 select HAVE_PAGE_SIZE_4KB select IRQ_DOMAIN select LOCK_MM_AND_FIND_VMA + select MMU_GATHER_RCU_TABLE_FREE select MODULES_USE_ELF_RELA select OF select OF_EARLY_FLATTREE diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig index 5eb995c13074..d90b24dd3bce 100644 --- a/arch/openrisc/Kconfig +++ b/arch/openrisc/Kconfig @@ -35,6 +35,7 @@ config OPENRISC select GENERIC_ATOMIC64 select GENERIC_CLOCKEVENTS_BROADCAST select GENERIC_SMP_IDLE_THREAD + select MMU_GATHER_RCU_TABLE_FREE select MODULES_USE_ELF_RELA select HAVE_DEBUG_STACKOVERFLOW select OR1K_PIC diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig index d60f1d5a94c0..204f64912f0e 100644 --- a/arch/sh/Kconfig +++ b/arch/sh/Kconfig @@ -61,6 +61,7 @@ config SUPERH select HAVE_SYSCALL_TRACEPOINTS select IRQ_FORCED_THREADING select LOCK_MM_AND_FIND_VMA + select MMU_GATHER_RCU_TABLE_FREE if MMU && !X2TLB select MODULES_USE_ELF_RELA select NEED_SG_DMA_LENGTH select NO_DMA if !MMU && !DMA_COHERENT --=20 2.55.0 From nobody Sat Sep 26 13:09:29 2026 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 B042025B08E; 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dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="eoW+Vg+q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8662C1F00A3F; Tue, 1 Sep 2026 11:05:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788260757; bh=+MMfaleDm2ce+ucIbxA7OEsrjCLcZrtuUhG+cgJq5Q4=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=eoW+Vg+qz0TYTuS8zmuLmeUVjLD9WlshmY+ZenPXLM12mbhI0Hz+5CrJFrOV2T9L2 DfnwpLRVXPJIJ5xaVjBq5RrsmTcN5BVQ+4BxNS3PRVo6vCXz2hTT7eoedZk9XGRGQ1 /Hkasly2r7zC5IrTB2wqqw1uFHDxP3VbX2vsjVwcbFzeA3v77TJUj0jUSwZmvH037w jo6A6EKvKBWWSb6p1boQBBN0eCIMaDEglu0JysxZO8jL0TOkjZDk8qLhnPrFePf9QW ZIEhpZKTn+4p45kDejAkDB20sutoUd3Rvy2sOql5HOjF+6fSnPjp3wrlW5fxVmRFG7 lIqFWgBbg/hiA== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 12:01:23 +0100 Subject: [PATCH 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: quoted-printable Message-Id: <20260901-rcu-pagetable-freeing-v1-3-5456a81c8212@kernel.org> References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> In-Reply-To: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@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 , Yoshinori Sato , 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 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 , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=1550; i=ljs@kernel.org; h=from:subject:message-id; bh=mgr1uJE8DIP+D2hAcn/4VQ8oaO28pfdyIohSciDSfkU=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmbXSXiAr54Z2+e3/IyQLbrwq3pEWNe54fXRhv7c9z+ eHq5ZPvd5SyMIhxMciKKbI8/yK+P0gkbF7nBX83mDmsTCBDGLg4BWAi810YGZ473c5+lTTPzG3p jyPOr7IEs8NnOJ08pckTV658qObJoxkM/ywtf19cV6htlbYgf/Gc6bMXCRs1LRUv98tOtcrY+Va nnAEA 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. 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 --=20 2.55.0 From nobody Sat Sep 26 13:09:29 2026 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 6566D47A0C7; Tue, 1 Sep 2026 11:06:13 +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=1788260774; cv=none; b=nBlNj8horas5OXaaCM/XOX14LYF49ZHJ0tJSanNzxX7orFNfCc9ldZ3+s4fnqvxv1uzS/FPQE47WncyPUsjSXwfN7uBO8x7uuENiThvZDUrr5/ZFflQs6o9/x9V319aujBjn4xPtNqEyPkt/eejUeuZmzw50c5HIKUuNKqpqCn4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788260774; c=relaxed/simple; bh=0gkFDBwGD1EYsdFXWdaAMN6hHbo1XQYIk0QvwnU2gCY=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=pDO2rGM9yFyP2qECiV1pxrbPDnZNpr3B1dyBvHT6jmZqytLaI5PyhZW5y/6sAgZ41b20lUt8SC/xH2XAhYDc2cPd80UwDrugpBnG3okqw1Ol8juAmyyd9sPru7LOaAEJ7m+gAOGLvOI4QankDcoC70x7LRp6qEwj3FDkYBsT7Lk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DiowDP1j; 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="DiowDP1j" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0F261F01562; Tue, 1 Sep 2026 11:05:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788260773; bh=GKPgtCS/jb8sy+IgthnzqZkszffWbth2i2OdMiXJ3aY=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=DiowDP1j1n5XlCF8U1bsHtuzN012sie75SVdXyIWaQX437ODGamaG8+dyw2U9ubLP ZQuORqY84alF4o7Xnb9l4E4w9MY0R9kv4cXPesYKeaO21X9V5t1J9jM6t8FOU6ikuy rwHNDo3oeWAPjqIeVWVsIP66njOhb+rnrhF3SVDfAj2sWhOXfEfEEsQfd1FnSFpSUT 7uyG08SrjLIgMgvGh2sqL3JbG7jtin7/mj29pE9PwuRoAAnOkJ79fImd5f8RrCs6l7 tyJFWeHJO81hWqDF+lZHR5ixipFciKy/9qPugDinCxm3vBNAzeRoHStXE0TrxYkfq2 AJel7eEB7e32g== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 12:01:24 +0100 Subject: [PATCH 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: quoted-printable Message-Id: <20260901-rcu-pagetable-freeing-v1-4-5456a81c8212@kernel.org> References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> In-Reply-To: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@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 , Yoshinori Sato , 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 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 , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=1932; i=ljs@kernel.org; h=from:subject:message-id; bh=0gkFDBwGD1EYsdFXWdaAMN6hHbo1XQYIk0QvwnU2gCY=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmbXQPjFVa63kgYD1nwDd5n/U/J56e/Sds1bv1xqzfk k9/K/rI01HKwiDGxSArpsjy/Iv4/iCRsHmdF/zdYOawMoEMYeDiFICJyKUzMjyZJ/zbXOdUdfG3 3lVZP8s03GYsefForppMeeA6s8AHPWsYGfYrl/n48ql+/h54kiNrev6UD/E3dxdvOxkQbW9aLfz amBcA 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. 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 --=20 2.55.0 From nobody Sat Sep 26 13:09:29 2026 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 8F23C31A55B; Tue, 1 Sep 2026 11:06:28 +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=1788260789; cv=none; b=N2S/QnA2kCdSZtmnhSw486XvJgkraV4URWVIkl/6jJLXpyqT2joeFhdSqGj6S/MOF6+OI5hRmbD1D0zLsEnifrofo/eQRCk8rC4O9RiCvA/HT/Yum1CKdR5MXgqCp1PpJhsV/gc6hxQ7PXrW0VND7ptqO/r59RcIbVcjcXWIrnw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788260789; c=relaxed/simple; bh=pmFGalV7u20s+FwKIjahThGo/bP2PelMktCxEOFxTVg=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=OdaI54HM6AHcEzqwRfNZXuCMIDPXYBwZuoob1NdjrO2jmMlCheTJ/3ZWnD7/mHPGEqqr+dfJRBLwQ8ojDY42/nD2biuoHQCW5tZVK+Etj0GfM6kWdtSkMrq9XOllsFWagouUUixpeltwB05Jdowyfrl74i6pQQ4CV9dsi+aG3rA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GGF50wlp; 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="GGF50wlp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 672D31F00A3D; Tue, 1 Sep 2026 11:06:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788260788; bh=TUQ/bqWjoWegxWt3AQb93fUpQ2PrCnmOoUsz1IYEEAE=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=GGF50wlpx5daBNc1SscpLRoU6tPHwKSR+bV8BmmnowzFMrNC7trXHUsfj3E29ekmP L994BAJdClVd9Yr3sw10ofz2hcYCefpn83H5DYofkntVOSN+eCftj5m4xWN3/2E2D/ RFukLQfk+qbv3V89PdpuaKKmQP74DUXJDElrDgI1Dr4MmMgC9t6XspOEhIOgtQX01M wqfpQbMB1i3sYccAi4FcWcGcNPqf/WvHnQU2Xsyz3ahXaqNeamxd9OXRjYTbFrxc7S /vIhMXRqAYVq0FTclNXFmznsm97gJHIBWu1Lt/sABxm5WcMKOwI4+HiU5LGFpA5f/L 7AiAMNGXxwKMQ== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 12:01:25 +0100 Subject: [PATCH 05/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for arc, microblaze, xtensa 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: quoted-printable Message-Id: <20260901-rcu-pagetable-freeing-v1-5-5456a81c8212@kernel.org> References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> In-Reply-To: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@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 , Yoshinori Sato , 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 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 , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=4476; i=ljs@kernel.org; h=from:subject:message-id; bh=pmFGalV7u20s+FwKIjahThGo/bP2PelMktCxEOFxTVg=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmbfSIvHmucsrngzpFV6ri1iXfOvHwlaZthq+1b/Z7h b/boqS4OkpZGMS4GGTFFFmefxHfHyQSNq/zgr8bzBxWJpAhDFycAnCROQx/pdWZM5/4V7cefbv6 30bLDceeu9TYfHEtfr1/o9qro+8EbzP8FfadW57HeKAhZnUIw8e+uFk5CVr6H1ZPr3eZnWD9uVm SCQA= X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Each of these architectures directly free page tables without routing these changes through tlb_remove_ptdesc(). The use of tlb_remove_ptdesc() is required for CONFIG_MMU_GATHER_RCU_TABLE_FREE to correctly free page tables under RCU, so simply update these architectures to use these functions. Since none of the architectures share page tables or do anything unusual, nothing complicated is required here. Therefore this is simply a mechanical change - convert __pud_free_tlb(), __pmd_free_tlb() and __pte_free_tlb() to use tlb_remove_ptdesc() as required. At the point this is in place, all mmu_gather page table freeing is performed under RCU, and thus MMU_GATHER_RCU_TABLE_FREE is selected for each architecture. This forms part of an overall effort to switch every architecture to this mode. Signed-off-by: Lorenzo Stoakes (ARM) --- arch/arc/Kconfig | 1 + arch/arc/include/asm/pgalloc.h | 6 +++--- arch/microblaze/Kconfig | 1 + arch/microblaze/include/asm/pgalloc.h | 2 +- arch/xtensa/Kconfig | 1 + arch/xtensa/include/asm/tlb.h | 2 +- 6 files changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig index 2ed7186c81c5..7a7542b61823 100644 --- a/arch/arc/Kconfig +++ b/arch/arc/Kconfig @@ -47,6 +47,7 @@ config ARC select HAVE_SYSCALL_TRACEPOINTS select IRQ_DOMAIN select LOCK_MM_AND_FIND_VMA + select MMU_GATHER_RCU_TABLE_FREE select MODULES_USE_ELF_RELA select OF select OF_EARLY_FLATTREE diff --git a/arch/arc/include/asm/pgalloc.h b/arch/arc/include/asm/pgalloc.h index dfae070fe8d5..9b6c37f92e97 100644 --- a/arch/arc/include/asm/pgalloc.h +++ b/arch/arc/include/asm/pgalloc.h @@ -72,7 +72,7 @@ static inline void p4d_populate(struct mm_struct *mm, p4d= _t *p4dp, pud_t *pudp) set_p4d(p4dp, __p4d((unsigned long)pudp)); } =20 -#define __pud_free_tlb(tlb, pmd, addr) pud_free((tlb)->mm, pmd) +#define __pud_free_tlb(tlb, pmd, addr) tlb_remove_ptdesc((tlb), virt_to_p= tdesc(pmd)) =20 #endif =20 @@ -83,10 +83,10 @@ static inline void pud_populate(struct mm_struct *mm, p= ud_t *pudp, pmd_t *pmdp) set_pud(pudp, __pud((unsigned long)pmdp)); } =20 -#define __pmd_free_tlb(tlb, pmd, addr) pmd_free((tlb)->mm, pmd) +#define __pmd_free_tlb(tlb, pmd, addr) tlb_remove_ptdesc((tlb), virt_to_p= tdesc(pmd)) =20 #endif =20 -#define __pte_free_tlb(tlb, pte, addr) pte_free((tlb)->mm, pte) +#define __pte_free_tlb(tlb, pte, addr) tlb_remove_ptdesc((tlb), page_ptde= sc(pte)) =20 #endif /* _ASM_ARC_PGALLOC_H */ diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig index 484ebb3baedf..af7e821e96c1 100644 --- a/arch/microblaze/Kconfig +++ b/arch/microblaze/Kconfig @@ -41,6 +41,7 @@ config MICROBLAZE select PCI_SYSCALL if PCI select CPU_NO_EFFICIENT_FFS select MMU_GATHER_NO_RANGE + select MMU_GATHER_RCU_TABLE_FREE select SPARSE_IRQ select ZONE_DMA select TRACE_IRQFLAGS_SUPPORT diff --git a/arch/microblaze/include/asm/pgalloc.h b/arch/microblaze/includ= e/asm/pgalloc.h index 084a8a0dc239..ffee6a009219 100644 --- a/arch/microblaze/include/asm/pgalloc.h +++ b/arch/microblaze/include/asm/pgalloc.h @@ -25,7 +25,7 @@ extern void __bad_pte(pmd_t *pmd); =20 extern pte_t *pte_alloc_one_kernel(struct mm_struct *mm); =20 -#define __pte_free_tlb(tlb, pte, addr) pte_free((tlb)->mm, (pte)) +#define __pte_free_tlb(tlb, pte, addr) tlb_remove_ptdesc((tlb), page_ptdes= c(pte)) =20 #define pmd_populate(mm, pmd, pte) \ (pmd_val(*(pmd)) =3D (unsigned long)page_address(pte)) diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig index f2f9cd9cde50..33c4caee30e2 100644 --- a/arch/xtensa/Kconfig +++ b/arch/xtensa/Kconfig @@ -55,6 +55,7 @@ config XTENSA select HAVE_VIRT_CPU_ACCOUNTING_GEN select IRQ_DOMAIN select LOCK_MM_AND_FIND_VMA + select MMU_GATHER_RCU_TABLE_FREE if MMU select MODULES_USE_ELF_RELA select PERF_USE_VMALLOC select TRACE_IRQFLAGS_SUPPORT diff --git a/arch/xtensa/include/asm/tlb.h b/arch/xtensa/include/asm/tlb.h index 8c3ceb427018..6fb7b78154f6 100644 --- a/arch/xtensa/include/asm/tlb.h +++ b/arch/xtensa/include/asm/tlb.h @@ -16,7 +16,7 @@ =20 #include =20 -#define __pte_free_tlb(tlb, pte, address) pte_free((tlb)->mm, pte) +#define __pte_free_tlb(tlb, pte, address) tlb_remove_ptdesc((tlb), page_pt= desc(pte)) =20 void check_tlb_sanity(void); =20 --=20 2.55.0 From nobody Sat Sep 26 13:09:29 2026 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 41F55318ED2; Tue, 1 Sep 2026 11:06:43 +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=1788260805; cv=none; b=dT5YQkeoI1I9ZNdLfPEF4JHglDrgWsVGI2QyhNws86cq+jrMPTNEF2EXGXxU+x5re/tlMdCXLugFGObbiRe57c5pW3Sn1pm5vgOF5ZYvASb1ZdfEtHtU8sXhWEebyCRdQq2dQ+XdlqTzPUqMpcjCAlDtT3Q8IRvb2+YsiV8yzoY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788260805; c=relaxed/simple; bh=+cl/mE+MMAULPxyBPFJXsNZLkn5nuULAZlZa1FGDhyY=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=TsvmhUNKkj9nAnqQ4O5K57aymB0o8GhfdGKQF6WeWHtQDTxKfF8dreBHksIZaLH7JoIufpv4vTX9RYASAsYMyC1U+RgL7gQ3AtJhokINhVa1Wq3RxU0LFu8UUwidhxzoLp7U+Jg31haM68goVdYPF1Y7y49v/7Ymsbcb2e3eXSo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NwoKGGKC; 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="NwoKGGKC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D00931F00A3E; Tue, 1 Sep 2026 11:06:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788260803; bh=2RQcemfGMYTiDH29zfMnTtdgj0bHtOblVlsFhLPlSxk=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=NwoKGGKCOsRyUU+EwJ2no2OGs9bmyTM35H3K9gIGh3HV4K+WdFczJU/eOXXaqSq6H k3HqUQSyYtmLNyQcKklEF3jOnimT477uPD5bPUrY3vzsO0q5rhBaHKvEzLmmOUoTeV LS7qc1mFdDW4R+qFz8GqeMqUV2SRfwucYXHjjwfClPVzkfmWmA7H119MkFGrVSiy2M 2i+O/pQmB8Q7TQ4gyhr2LkP3WlwncZC4EvmV+llTIKpVYZ5j7ph1KajtR0mHJjWcp3 C3dGZ4dAndriF5N79xdeqD4sLGWw6jUMW2TMEdqkRBXSUrwPC8mBLnJDj1WCNUN1fk Lsp1rzKfB8Lug== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 12:01:26 +0100 Subject: [PATCH 06/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for sparc64 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: quoted-printable Message-Id: <20260901-rcu-pagetable-freeing-v1-6-5456a81c8212@kernel.org> References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> In-Reply-To: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@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 , Yoshinori Sato , 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 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 , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=2421; i=ljs@kernel.org; h=from:subject:message-id; bh=+cl/mE+MMAULPxyBPFJXsNZLkn5nuULAZlZa1FGDhyY=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmbfRoWHu8+2WMGXd53Frn2Q/TfRbbcH08FO0d/tq/O 1w/w3BqRykLgxgXg6yYIsvzL+L7g0TC5nVe8HeDmcPKBDKEgYtTACYiZcjIcH3mqoOd6vvZeHat LZwryGV6VWy+UWngii1a17n6ItznP2H4Z1P/w3/OzVMba8P0LaVSbs6x8uGbP2Ph03esF2VqH2r JMQMA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Commit 4a0100f7546f ("sparc64: use RCU page table freeing") enabled CONFIG_MMU_GATHER_RCU_TABLE_FREE for SMP sparc64 architectures, expressly for GUP-fast page table walkers. Naturally, UP systems do not have to worry about concurrent GUP fast operations. However, CONFIG_PREEMPT_RCU is also available even on a UP system, so a future pure-RCU page table walker requires MMU_GATHER_RCU_TABLE_FREE to be enabled on UP, even if concurrent GUP fast is not possible there. To enable future pure-RCU page table walkers, enable MMU_GATHER_RCU_TABLE_FREE unconditionally. With this change, it is no longer necessary to have !CONFIG_SMP pgtable_free_tlb(), so also remove this now dead code. This forms part of an overall effort to switch every architecture to this mode. Signed-off-by: Lorenzo Stoakes (ARM) --- arch/sparc/Kconfig | 4 ++-- arch/sparc/include/asm/pgalloc_64.h | 8 -------- 2 files changed, 2 insertions(+), 10 deletions(-) diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig index ab77d3f2536e..8d42ebc6d302 100644 --- a/arch/sparc/Kconfig +++ b/arch/sparc/Kconfig @@ -75,8 +75,8 @@ config SPARC64 select HAVE_FUNCTION_GRAPH_TRACER select HAVE_KRETPROBES select HAVE_KPROBES - select MMU_GATHER_RCU_TABLE_FREE if SMP - select HAVE_ARCH_TLB_REMOVE_TABLE if SMP + select MMU_GATHER_RCU_TABLE_FREE + select HAVE_ARCH_TLB_REMOVE_TABLE select MMU_GATHER_MERGE_VMAS select MMU_GATHER_NO_FLUSH_CACHE select HAVE_ARCH_TRANSPARENT_HUGEPAGE diff --git a/arch/sparc/include/asm/pgalloc_64.h b/arch/sparc/include/asm/p= galloc_64.h index caa7632be4c2..b5055d259b74 100644 --- a/arch/sparc/include/asm/pgalloc_64.h +++ b/arch/sparc/include/asm/pgalloc_64.h @@ -74,8 +74,6 @@ void pte_free_defer(struct mm_struct *mm, pgtable_t pgtab= le); =20 void pgtable_free(void *table, bool is_page); =20 -#ifdef CONFIG_SMP - struct mmu_gather; void tlb_remove_table(struct mmu_gather *, void *); =20 @@ -96,12 +94,6 @@ static inline void __tlb_remove_table(void *_table) is_page =3D true; pgtable_free(table, is_page); } -#else /* CONFIG_SMP */ -static inline void pgtable_free_tlb(struct mmu_gather *tlb, void *table, b= ool is_page) -{ - pgtable_free(table, is_page); -} -#endif /* !CONFIG_SMP */ =20 static inline void __pte_free_tlb(struct mmu_gather *tlb, pte_t *pte, unsigned long address) --=20 2.55.0 From nobody Sat Sep 26 13:09:29 2026 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 C0B7F429825; Tue, 1 Sep 2026 11:06:59 +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=1788260821; cv=none; b=YE1/d6IduHMHx3nr/N5lodoyFxuTAD+6f7j3eJoBTIbpNUjbpLu7rDhx4BvLGuZbWLNosn/6NwAPhqvl7t1bh8qS/7K26V3jKr8mZmay7tLBAxUB/fpe1wy6ip7R3NPMVHHG8vHh8m8rYE2WirXZjGhAqRdLtrPZxQX3sjA4WDI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788260821; c=relaxed/simple; bh=qTT+GrBJ7CN/0g7aihQa6c1ZdVlLMdQ0LNJ7aV+6CtQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=XXaqDqtNNuz4uVKDSQw73DXi6Ov4zTrKfFU6aoOXdeRBGsGR8JybEiij8N1ofEpaBBSHvXs4H6z9gJnx8vn0yHfzy3Qkn7NcKygrO4RWBgfI0GDEjS1mIG4wQ74QUcpdJY7St7cN5S1YDHPDvt7eI1TZcfHSHqIFU4PRanBG3TY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XD3oyzIY; 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="XD3oyzIY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 41FFE1F000E9; Tue, 1 Sep 2026 11:06:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788260819; bh=1aimUPxzYaTPXtJhtWkzW57/+8qeslpkAUz+f7GK8/Y=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=XD3oyzIY4msLPQ772JhwLo0AmvI8pJiExLU3e3acDjohAHfqAlS9rlSLlt64WVSfM r3kRTCUYRFXtwdrLXLd4zIwibTfWMnW/NDIIYUE6lAId+LAAlnedVWBr2YfRCEVFnh NaU4l0p6UGv9r8gy6ABLmcwKqZFw1aYx2Pz8fy8/zPMOSd7woDX9/45BsOq29uxCFH t67glyPsR7yypFVn1RgslLR+rEAEHQj1J/iNjz4RcFE6+mZcsM+M0zD52vr+Us6TCk T4FBgX6sN7RoaCrUvJ6hGpa6JR9artGVasWEmFWwFE4AH8UoYRgRo/FGT9ifPsbukd aB6GG57pdUC3g== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 12:01:27 +0100 Subject: [PATCH 07/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for m68k-coldfire 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: quoted-printable Message-Id: <20260901-rcu-pagetable-freeing-v1-7-5456a81c8212@kernel.org> References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> In-Reply-To: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@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 , Yoshinori Sato , 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 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 , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=1842; i=ljs@kernel.org; h=from:subject:message-id; bh=qTT+GrBJ7CN/0g7aihQa6c1ZdVlLMdQ0LNJ7aV+6CtQ=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmbfQIULyUGXJvk7x6z/RM7Xe7feOXy31ul/W6IvyVo XSrazZ/RykLgxgXg6yYIsvzL+L7g0TC5nVe8HeDmcPKBDKEgYtTACbSGsnw33vZ/N1+HBlPyg4d Z9inYfllvWvq5p/7s6qbX3+3iw4rCWRkmG8v0yi5/9js5G+fUmMi34cp/96XPWefUlWg8e7Pkmm cjAA= X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Similar to sun3, the coldfire variant of m68k uses 2-level page tables. Update its __pte_free_tlb() function to use tlb_remove_ptdesc() in order that, with CONFIG_MMU_GATHER_RCU_TABLE_FREE, page tables are freed under RCU. The page tables occupy a page each and have no odd semantics, so this change suffices to allow enabling of CONFIG_MMU_GATHER_RCU_TABLE_FREE for m68k-coldfire, so do so. This forms part of an overall effort to switch every architecture to this mode. Signed-off-by: Lorenzo Stoakes (ARM) --- arch/m68k/Kconfig | 2 +- arch/m68k/include/asm/mcf_pgalloc.h | 5 +---- 2 files changed, 2 insertions(+), 5 deletions(-) diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig index e29610fd1240..6b8ec67c86fd 100644 --- a/arch/m68k/Kconfig +++ b/arch/m68k/Kconfig @@ -36,7 +36,7 @@ config M68K select HAVE_MOD_ARCH_SPECIFIC select HAVE_UID16 select MMU_GATHER_NO_RANGE if MMU - select MMU_GATHER_RCU_TABLE_FREE if MMU && SUN3 + select MMU_GATHER_RCU_TABLE_FREE if MMU && (SUN3 || COLDFIRE) select MODULES_USE_ELF_REL select MODULES_USE_ELF_RELA select NO_DMA if !MMU && !COLDFIRE diff --git a/arch/m68k/include/asm/mcf_pgalloc.h b/arch/m68k/include/asm/mc= f_pgalloc.h index fc5454d37da3..b53ff0950db2 100644 --- a/arch/m68k/include/asm/mcf_pgalloc.h +++ b/arch/m68k/include/asm/mcf_pgalloc.h @@ -39,10 +39,7 @@ extern inline pmd_t *pmd_alloc_kernel(pgd_t *pgd, unsign= ed long address) static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pgtabl= e, unsigned long address) { - struct ptdesc *ptdesc =3D virt_to_ptdesc(pgtable); - - pagetable_dtor(ptdesc); - pagetable_free(ptdesc); + tlb_remove_ptdesc(tlb, virt_to_ptdesc(pgtable)); } =20 static inline pgtable_t pte_alloc_one(struct mm_struct *mm) --=20 2.55.0 From nobody Sat Sep 26 13:09:29 2026 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 B37B237E5DC; Tue, 1 Sep 2026 11:07:14 +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=1788260837; cv=none; b=qfJ+lk4hgGKwnvxpr47/eZ1ov9s9AuAQ/nQD2VxdKpGCK6o5SEP9myxbOUZIQGNl3QnEW222ozyh82/UQHcXnQppRdNt3u2Lx/Li0Q5F6QEEMAFNErXTAvleY2wc+r95BaJedViMkylwQOpBDMgUMBanx6ZYaoEb2WjXVwRBFPI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788260837; c=relaxed/simple; bh=wpROf24w3fAQ7cNDxi2SGsbF1TZYrv0Ll+LdZO5C4PE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=neyBaA40orujBCAT80clkwrLs049l4k/5EwM84MnIyqMgEZq2faB3dWYuWYB5hN5hUwGFFEN6ID/mojSm1+TUJiN1gs8r+mWY6rHT0SeWljJ476jrXA/TcoMt2Q9sgrhylSZMZnf/tqpbGIq81t1ar/OpZfeUu4c++AbvHyE7/M= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fKcC35If; 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="fKcC35If" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB3661F00A3E; Tue, 1 Sep 2026 11:06:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788260834; bh=NpWdcIey4xCI1AAiZQP3vw2H/6eRNpO9q4dcacOYsLQ=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=fKcC35If/CtvKChvqt5gUvqvorcc35uBsHqFaoGPqLbiuylQdAEfGO/G5E+6idRQN 34UBrVl0XrBauS51NgMCTWbZU0DLB7faiJbbqAB7l0KmaZOMIY7Ulwpk3r5RuNtz0N eCm7a/Rk3wqb5TFyn0BlOEXPprS22p9u9qa5KPK9ow489ArtoKwNG0RygpFPB5fdjD xE2TDdfkkTxWDpZ5LX4CSAN6qksgUVkiaekknySbV4Bxdpm7H7bkGacdSps6MCu8mN 1S20jBBhqJlJA+jIArUyFc7z8VBwFYgsNH5bZv/ggaKXNYDy32b9Z5G6IbLpu2LLtH pUdonUJS5p+6g== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 12:01:28 +0100 Subject: [PATCH 08/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for sh-X2 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: quoted-printable Message-Id: <20260901-rcu-pagetable-freeing-v1-8-5456a81c8212@kernel.org> References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> In-Reply-To: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@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 , Yoshinori Sato , 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 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 , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=4126; i=ljs@kernel.org; h=from:subject:message-id; bh=wpROf24w3fAQ7cNDxi2SGsbF1TZYrv0Ll+LdZO5C4PE=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmbfTY3rBju4Bd4BKvOA7GJCfm9T3b5ft/f1wYWJjuG z0p5uuyjlIWBjEuBlkxRZbnX8T3B4mEzeu84O8GM4eVCWQIAxenAExE/jDDf4+p69lmSPrUvtu7 JHk1e3DdtdYCzhnb7DJOt1oujv9/u53hD39LvqLvpsWJzapJ87dcr3/goHf2zLSK0s+T9P21Vjz bwwwA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Currently, non-x2 sh specifies CONFIG_MMU_GATHER_RCU_TABLE_FREE allowing RCU page table freeing. sh-X2 is problematic because it utilises slab-allocated PMD page tables, and thus tlb_remove_ptdesc() cannot be used in these cases. All other sh variants are fine as commit e3ecf7c7d082 ("mm: pgtable: convert some architectures to use tlb_remove_ptdesc()") already converted page table freeing to use tlb_remove_ptdesc(), which does so after an RCU grace period when CONFIG_MMU_GATHER_RCU_TABLE_FREE is specified. Resolve this issue by firstly specifying CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE for sh-X2, so the arch can provide its own __tlb_remove_table() implementation (called after the RCU grace period). Then, convert __pmd_free_tlb() to tag the pointer to the PMD, and have __tlb_remove_table() check this tag to determine whether to free via the slab or to use pagetable_dtor_free(). This follows the pattern used by sparc64 as implemented in commit 4a0100f7546f ("sparc64: use RCU page table freeing"). Previously __pmd_free_tlb() freed PMD page tables immediately, before any TLB flush IPI. This seems to be a pre-existing bug, which this change also resolves. CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE is only specified for sh-X2, as setting it disables CONFIG_PT_RECLAIM and causes __tlb_remove_table_one() to call tlb_remove_table_sync_rcu() and synchronize_rcu() in turn, and this is not necessary for other sh variants. This forms part of an overall effort to switch every architecture to this mode. Signed-off-by: Lorenzo Stoakes (ARM) --- arch/sh/Kconfig | 3 ++- arch/sh/include/asm/pgalloc.h | 6 +++++- arch/sh/mm/pgtable.c | 20 ++++++++++++++++++++ 3 files changed, 27 insertions(+), 2 deletions(-) diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig index 204f64912f0e..75236bef6f16 100644 --- a/arch/sh/Kconfig +++ b/arch/sh/Kconfig @@ -33,6 +33,7 @@ config SUPERH select HAVE_ARCH_AUDITSYSCALL select HAVE_ARCH_KGDB select HAVE_ARCH_SECCOMP_FILTER + select HAVE_ARCH_TLB_REMOVE_TABLE if X2TLB select HAVE_ARCH_TRACEHOOK select HAVE_DEBUG_BUGVERBOSE select HAVE_DEBUG_KMEMLEAK @@ -61,7 +62,7 @@ config SUPERH select HAVE_SYSCALL_TRACEPOINTS select IRQ_FORCED_THREADING select LOCK_MM_AND_FIND_VMA - select MMU_GATHER_RCU_TABLE_FREE if MMU && !X2TLB + select MMU_GATHER_RCU_TABLE_FREE if MMU select MODULES_USE_ELF_RELA select NEED_SG_DMA_LENGTH select NO_DMA if !MMU && !DMA_COHERENT diff --git a/arch/sh/include/asm/pgalloc.h b/arch/sh/include/asm/pgalloc.h index 6fe7123d38fa..67ce7fa23fa1 100644 --- a/arch/sh/include/asm/pgalloc.h +++ b/arch/sh/include/asm/pgalloc.h @@ -17,7 +17,11 @@ extern void pgd_free(struct mm_struct *mm, pgd_t *pgd); extern void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd); extern pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address); extern void pmd_free(struct mm_struct *mm, pmd_t *pmd); -#define __pmd_free_tlb(tlb, pmdp, addr) pmd_free((tlb)->mm, (pmdp)) +extern void __tlb_remove_table(void *table); + +/* PMDs are slab-allocated, tag so they are freed correctly. */ +#define __pmd_free_tlb(tlb, pmdp, addr) \ + tlb_remove_table((tlb), (void *)((unsigned long)(pmdp) | 1)) #endif =20 static inline void pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmd, diff --git a/arch/sh/mm/pgtable.c b/arch/sh/mm/pgtable.c index 3a4085ea0161..f6184b86b89c 100644 --- a/arch/sh/mm/pgtable.c +++ b/arch/sh/mm/pgtable.c @@ -56,4 +56,24 @@ void pmd_free(struct mm_struct *mm, pmd_t *pmd) { kmem_cache_free(pmd_cachep, pmd); } + +static void __tlb_remove_table_slab(void *table) +{ + kmem_cache_free(pmd_cachep, table); +} + +static void __tlb_remove_table_pgtable(void *table) +{ + pagetable_dtor_free(table); +} + +void __tlb_remove_table(void *table) +{ + const unsigned long addr =3D (unsigned long)table; + + if (addr & 1) + __tlb_remove_table_slab((void *)(addr & ~1UL)); + else + __tlb_remove_table_pgtable(table); +} #endif /* PAGETABLE_LEVELS > 2 */ --=20 2.55.0 From nobody Sat Sep 26 13:09:29 2026 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 85F4531355C; Tue, 1 Sep 2026 11:07:30 +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=1788260852; cv=none; b=P+wn52kcXDR/iXnEC5nD+wb6hgHHOVcZEHhJxrwI3h3IsFgeE9AeBDSi4BLL0QoaqYVno5m1CKPR4pcfmhcL5djZXpAHmPkkima3Win2cYJTP1nbvJBmPSyfOEIzBYUfLcCqc0vfZoIFFTOIh7CKXy6VdC1N/ICqrGXnFxaSzME= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788260852; c=relaxed/simple; bh=YPp0BOY0cp4Ahu0Pm+BSyaylIhdW6d3HcAy3HzwYfuo=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=UEe9r9vwwravMk+AIXlKtIHJFIfQW7KOjrOY3YzDBRZkPyDy3Y22JDqb2oJcNrYMblU4qS2AH1qDTmzBHbIsH+m5ncaLQSiMYMTVjj9s7IGXbmIktWQP0syDLTsL8qw4swZYiZRmUb+MKuFdbku704qDPosnaK5tWN7iNjZtIEU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=H1Cp4bcm; 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="H1Cp4bcm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 22BA41F00A3D; Tue, 1 Sep 2026 11:07:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788260850; bh=r59pxQpc2HnO7g8Xd7SmTRKFCMfW6qlwbRKzNqikO1A=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=H1Cp4bcmyCtPW3T967T/dgqInT+lD+ja2MqM8qvjYKkjn2y8MQTBvrVCi43cnoMXJ lxDSQMKkx8p1rA+yfYLyqUJEM5wnp1buvYhxr8/h3sjljAFHjsvRB6CkC+D0/6kJvp V8zJ7ykWZV1H8L9XGaqV5WgYAizOoUUwD6HDxUF5s/SvGnESx8vadxQtv8oKbJcss8 iaA6UgU3ggYAwwS0JavyArsKHm5ifn06ozLQn2Z7iFmC6mxogJ/9yLfBa13YI9JDZH /sJkWHceVV10ham6kQffhRSd9kFVD8F2MdTdTXjFO8eY84x/9WftMvuGeCLR44cMiQ ZIRGFY9AOpPfg== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 12:01:29 +0100 Subject: [PATCH 09/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for m68k-motorola 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: quoted-printable Message-Id: <20260901-rcu-pagetable-freeing-v1-9-5456a81c8212@kernel.org> References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> In-Reply-To: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@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 , Yoshinori Sato , 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 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 , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=9513; i=ljs@kernel.org; h=from:subject:message-id; bh=YPp0BOY0cp4Ahu0Pm+BSyaylIhdW6d3HcAy3HzwYfuo=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmbfTQn/30mM/8yPBbvc8OX2I78TfwT55CxB7fpCxHL XPTC5JnO0pZGMS4GGTFFFmefxHfHyQSNq/zgr8bzBxWJpAhDFycAjCR1UcZGa57Nuob+61nWhNw j0dBZPIbnrq50Tc3Cj024tnCFMMZepCR4drlO3d7e8szGCwPsScfybkb6D+/NuVfRcbZWxz/3Jm +swMA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 sun3 and coldfire are already supported, however motorola requires a little more care. Here, custom table removal logic is required, so CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE is enabled for m68k-motorola. Firstly as part of this change, the page table level must be communicated to the underlying __tlb_remove_table() implementation. Take advantage of the fact that page tables are aligned by more than enough to permit setting TABLE_PTE or TABLE_PMD in the low bits of the pointer, and store this there. Then update __pte_free_tlb() and __pmd_free_tlb() to pass this through, then have __tlb_remove_table() decode this and pass it to free_pointer_table(). The page table freeing is performed via call_rcu(), so free_pointer_table() now will be invoked from softirq context, and as such may be re-entrant. Introduce an irq save/restore spinlock to handle this, and hold it over the time a given ptable entry is being referenced in both get_pointer_table() and free_pointer_table(). In order to make things a little easier in this respect, separate out the logic for adding a new ptable entry into add_pointer_table() and only hold the lock during ptable entry insertion in this case. Note that original list_add_tail(new, dp) added new prior to dp, which is ptable_list[type].next, i.e. after ptable_list[type]. The equivalent therefore is list_add(new, &ptable_list[type]), which adds new after ptable_list[type], only without needing to make reference to dp. Note that, as m68k-motorola specifies CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE, it does not enable CONFIG_PT_RECLAIM. This isn't meaningfully impactful. With this applied, all of m68k implements CONFIG_MMU_GATHER_RCU_TABLE_FREE. This forms part of an overall effort to switch every architecture to this mode. Signed-off-by: Lorenzo Stoakes (ARM) --- arch/m68k/Kconfig | 3 +- arch/m68k/include/asm/motorola_pgalloc.h | 9 ++- arch/m68k/mm/motorola.c | 121 ++++++++++++++++++++-------= ---- 3 files changed, 86 insertions(+), 47 deletions(-) diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig index 6b8ec67c86fd..fa5d39549da9 100644 --- a/arch/m68k/Kconfig +++ b/arch/m68k/Kconfig @@ -29,6 +29,7 @@ config M68K select HAVE_ARCH_LIBGCC_H select HAVE_ARCH_SECCOMP select HAVE_ARCH_SECCOMP_FILTER + select HAVE_ARCH_TLB_REMOVE_TABLE if MMU_MOTOROLA select HAVE_ASM_MODVERSIONS select HAVE_DEBUG_BUGVERBOSE select HAVE_EFFICIENT_UNALIGNED_ACCESS if !CPU_HAS_NO_UNALIGNED @@ -36,7 +37,7 @@ config M68K select HAVE_MOD_ARCH_SPECIFIC select HAVE_UID16 select MMU_GATHER_NO_RANGE if MMU - select MMU_GATHER_RCU_TABLE_FREE if MMU && (SUN3 || COLDFIRE) + select MMU_GATHER_RCU_TABLE_FREE if MMU select MODULES_USE_ELF_REL select MODULES_USE_ELF_RELA select NO_DMA if !MMU && !COLDFIRE diff --git a/arch/m68k/include/asm/motorola_pgalloc.h b/arch/m68k/include/a= sm/motorola_pgalloc.h index 1091fb0affbe..dcde40e8b5c6 100644 --- a/arch/m68k/include/asm/motorola_pgalloc.h +++ b/arch/m68k/include/asm/motorola_pgalloc.h @@ -17,6 +17,7 @@ enum m68k_table_types { extern void init_pointer_table(void *table, int type); extern void *get_pointer_table(struct mm_struct *mm, int type); extern int free_pointer_table(void *table, int type); +extern void __tlb_remove_table(void *table); =20 /* * Allocate and free page tables. The xxx_kernel() versions are @@ -47,7 +48,7 @@ static inline void pte_free(struct mm_struct *mm, pgtable= _t pgtable) static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pgtabl= e, unsigned long address) { - free_pointer_table(pgtable, TABLE_PTE); + tlb_remove_table(tlb, (void *)((unsigned long)pgtable | TABLE_PTE)); } =20 =20 @@ -61,10 +62,10 @@ static inline int pmd_free(struct mm_struct *mm, pmd_t = *pmd) return free_pointer_table(pmd, TABLE_PMD); } =20 -static inline int __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd, - unsigned long address) +static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd, + unsigned long address) { - return free_pointer_table(pmd, TABLE_PMD); + tlb_remove_table(tlb, (void *)((unsigned long)pmd | TABLE_PMD)); } =20 =20 diff --git a/arch/m68k/mm/motorola.c b/arch/m68k/mm/motorola.c index b30aa69a73a6..ffc80483440b 100644 --- a/arch/m68k/mm/motorola.c +++ b/arch/m68k/mm/motorola.c @@ -20,6 +20,7 @@ #include #include #include +#include =20 #include #include @@ -103,6 +104,8 @@ static struct list_head ptable_list[3] =3D { LIST_HEAD_INIT(ptable_list[2]), }; =20 +static DEFINE_SPINLOCK(ptable_lock); + #define PD_PTABLE(ptdesc) ((ptable_desc *)&(virt_to_ptdesc((void *)(ptdesc= ))->pt_list)) #define PD_PTDESC(ptable) (list_entry(ptable, struct ptdesc, pt_list)) #define PD_MARKBITS(dp) (*(unsigned int *)&PD_PTDESC(dp)->pt_index) @@ -139,52 +142,66 @@ void __init init_pointer_table(void *table, int type) return; } =20 -void *get_pointer_table(struct mm_struct *mm, int type) +/* + * For a pointer table for a user process address space, a + * table is taken from a ptdesc allocated for the purpose. Each + * ptdesc can hold 8 pointer tables. The ptdesc is remapped in + * virtual address space to be noncacheable. + */ +static void *add_pointer_table(struct mm_struct *mm, int type) { - ptable_desc *dp =3D ptable_list[type].next; - unsigned int mask =3D list_empty(&ptable_list[type]) ? 0 : PD_MARKBITS(dp= ); - unsigned int tmp, off; + struct ptdesc *ptdesc; + ptable_desc *new; + void *pt_addr; =20 - /* - * For a pointer table for a user process address space, a - * table is taken from a ptdesc allocated for the purpose. Each - * ptdesc can hold 8 pointer tables. The ptdesc is remapped in - * virtual address space to be noncacheable. - */ - if (mask =3D=3D 0) { - struct ptdesc *ptdesc; - ptable_desc *new; - void *pt_addr; - - ptdesc =3D pagetable_alloc(GFP_KERNEL | __GFP_ZERO, 0); - if (!ptdesc) - return NULL; - - pt_addr =3D ptdesc_address(ptdesc); - - switch (type) { - case TABLE_PTE: - /* - * m68k doesn't have SPLIT_PTE_PTLOCKS for not having - * SMP. - */ - pagetable_pte_ctor(mm, ptdesc); - break; - case TABLE_PMD: - pagetable_pmd_ctor(mm, ptdesc); - break; - case TABLE_PGD: - pagetable_pgd_ctor(ptdesc); - break; - } + ptdesc =3D pagetable_alloc(GFP_KERNEL | __GFP_ZERO, 0); + if (!ptdesc) + return NULL; + + pt_addr =3D ptdesc_address(ptdesc); + + switch (type) { + case TABLE_PTE: + /* + * m68k doesn't have SPLIT_PTE_PTLOCKS for not having + * SMP. + */ + pagetable_pte_ctor(mm, ptdesc); + break; + case TABLE_PMD: + pagetable_pmd_ctor(mm, ptdesc); + break; + case TABLE_PGD: + pagetable_pgd_ctor(ptdesc); + break; + } + + mmu_page_ctor(pt_addr); + + new =3D PD_PTABLE(pt_addr); =20 - mmu_page_ctor(pt_addr); + PD_MARKBITS(new) =3D ptable_mask(type) - 1; + scoped_guard(spinlock_irqsave, &ptable_lock) + list_add(new, &ptable_list[type]); =20 - new =3D PD_PTABLE(pt_addr); - PD_MARKBITS(new) =3D ptable_mask(type) - 1; - list_add_tail(new, dp); + return (pmd_t *)pt_addr; +} + +void *get_pointer_table(struct mm_struct *mm, int type) +{ + unsigned int tmp, off; + unsigned long mask; + unsigned long flags; + ptable_desc *dp; + void *ret; =20 - return (pmd_t *)pt_addr; + spin_lock_irqsave(&ptable_lock, flags); + dp =3D ptable_list[type].next; + mask =3D list_empty(&ptable_list[type]) ? 0 : PD_MARKBITS(dp); + + if (mask =3D=3D 0) { + spin_unlock_irqrestore(&ptable_lock, flags); + return add_pointer_table(mm, type); } =20 for (tmp =3D 1, off =3D 0; (mask & tmp) =3D=3D 0; tmp <<=3D 1, off +=3D p= table_size(type)) @@ -194,7 +211,10 @@ void *get_pointer_table(struct mm_struct *mm, int type) /* move to end of list */ list_move_tail(dp, &ptable_list[type]); } - return ptdesc_address(PD_PTDESC(dp)) + off; + + ret =3D ptdesc_address(PD_PTDESC(dp)) + off; + spin_unlock_irqrestore(&ptable_lock, flags); + return ret; } =20 int free_pointer_table(void *table, int type) @@ -203,6 +223,9 @@ int free_pointer_table(void *table, int type) unsigned long ptable =3D (unsigned long)table; unsigned long pt_addr =3D ptable & PAGE_MASK; unsigned int mask =3D 1U << ((ptable - pt_addr)/ptable_size(type)); + unsigned long flags; + + spin_lock_irqsave(&ptable_lock, flags); =20 dp =3D PD_PTABLE(pt_addr); if (PD_MARKBITS (dp) & mask) @@ -213,6 +236,8 @@ int free_pointer_table(void *table, int type) if (PD_MARKBITS(dp) =3D=3D ptable_mask(type)) { /* all tables in ptdesc are free, free ptdesc */ list_del(dp); + spin_unlock_irqrestore(&ptable_lock, flags); + mmu_page_dtor((void *)pt_addr); pagetable_dtor_free(virt_to_ptdesc((void *)pt_addr)); return 1; @@ -223,9 +248,21 @@ int free_pointer_table(void *table, int type) */ list_move(dp, &ptable_list[type]); } + + spin_unlock_irqrestore(&ptable_lock, flags); return 0; } =20 +void __tlb_remove_table(void *table) +{ + /* The bottom 2 bits are used to encode page table type. */ + const unsigned long encoded =3D (unsigned long)table; + void *addr =3D (void *)(encoded & ~3UL); + const int type =3D encoded & 3; + + free_pointer_table(addr, type); +} + /* size of memory already mapped in head.S */ extern __initdata unsigned long m68k_init_mapped_size; =20 --=20 2.55.0 From nobody Sat Sep 26 13:09:29 2026 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 E896134C155; Tue, 1 Sep 2026 11:07:45 +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=1788260867; cv=none; b=H0tM+ibeTt6Ayd5WaNDRZ1L6H7pxcXOiJAlVgp/rzRZypqJ38w+q3FqcvlqxOGz4cjLvPJnwZ4xS0E40T3Cnl1vEqe3w0cpz44AqUvM4ABpydrW7m7+PZ5rJL3+2PKeJx8ED8SoGFCEJ6EoIbU2eebbjPOeVV17jQtpyzYXF1Ng= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788260867; c=relaxed/simple; bh=xq+2kEjitK8SahcerAyiHbVRI8AjRac23jnTjhfS/aE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=ZSTktbOzMV3dsmJjXsfSNTCXFBVmsR8W8iIQWDw3PMsXTLoFmHLTHs9uSfrRhc2RfWRJJHGzPOknZOOfeVGgjhm1ReCeqO2xwvlE+qSOqQ3qjB0QAdEhZddsWOftVIOvVXPNpGxew20VOFqlitslhnVMHndY7T9lh+QmU33VEIg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ibERjQL4; 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="ibERjQL4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 890D11F00A3E; Tue, 1 Sep 2026 11:07:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788260865; bh=UzmfMP0eW0QWk8u/JUsvHFB9sPVEd1pOiiGI1COzZqo=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=ibERjQL4ebquAOt5buU64F486oqWBbfA2RuIUoKFTjhNX1tV+wd/vlzXzB2ChZkHv l81wOM2a96hacFPMbPkyXXoBNm2Hzxv/W4WdF2hM2MLHWeDUUI22Hgh/Uo2UP3EmsH 6u1tLsmWjj175oxrugx4dQMXcTyodnPkdmSqOUnAv5k4zRONX/wRi1k1UeQuFDk4c9 TOGuMPYZqERpof+Ma0CoF75P9Vb9bB8N/xhQG1X3/ETHZGTwbbnr8eP5HjxNvuOWvr /232U2NeMflD6ulot7zvWwwBLRdnsYSIvu9ACtq65I/v7n2wSL/1Kx7ZypCDDNaPUx Gislm4zUwKcZg== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 12:01:30 +0100 Subject: [PATCH 10/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for sparc32 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: quoted-printable Message-Id: <20260901-rcu-pagetable-freeing-v1-10-5456a81c8212@kernel.org> References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> In-Reply-To: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@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 , Yoshinori Sato , 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 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 , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=7123; i=ljs@kernel.org; h=from:subject:message-id; bh=xq+2kEjitK8SahcerAyiHbVRI8AjRac23jnTjhfS/aE=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmbfT4euup8O4LE9bU9LjsfrJFU1mER6vr92f+zX6eX qX5n58u6ShlYRDjYpAVU2R5/kV8f5BI2LzOC/5uMHNYmUCGMHBxCsBElvUwMjybUD2LVcBQ48G7 BZN/xmmFneuLef1v1fMzj2ztbS0rVYIY/pd9TjZcoH2Mr77xm173C4uZ32aLBbl5TK7+IBjx9UG yKTcA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Careful handling is required for sparc32 which implements page tables as part of a shared backing page. To support this, a custom __tlb_remove_table() function is required, as specified by CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE. This allows __pte_free_tlb() and __pmd_free_tlb() to specify which page table level is being freed, which is transmitted to __tlb_remove_table() through setting the lowest bit of the page table to 1 for a PMD and 0 for a PTE (the page tables are 256-byte aligned so this is safe to do). Next, since the page table freeing is done via RCU callback, and thus might be executed in softirq context, update the spin locks to IRQ save/restore. Then, in __tlb_remove_table(), figure out whether to free a PMD page table via free_pmd_fast() or a PTE via the newly introduced __pte_free() function, using the lower bit encoded in __pte_free_tlb() or __pmd_free_tlb() to determine which to call. __pte_free() is identical to preexisting pte_free(), except that it optionally allows a NULL mm pointer to be provided, in which case there is no mm whose mm->page_table_lock can be taken. This lock doesn't appear to have been doing quite as much as it intended, as backing pages can contain page tables for multiple mm's, which are not serialised by it. But more importantly - the reference count increment in pte_alloc_one() and decrement in __pte_free() are atomic with full ordering, so it simply isn't possible for there to be a meaningful race here. Note that the specification of CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE disables CONFIG_PT_RECLAIM for sparc32, which mirrors sparc64. This forms part of an overall effort to switch every architecture to this mode, and with it complete, means every architecture now supports CONFIG_MMU_GATHER_RCU_TABLE_FREE. Signed-off-by: Lorenzo Stoakes (ARM) --- arch/sparc/Kconfig | 2 ++ arch/sparc/include/asm/pgalloc_32.h | 7 +++++-- arch/sparc/lib/bitext.c | 14 +++++++------- arch/sparc/mm/srmmu.c | 26 +++++++++++++++++++++++--- 4 files changed, 37 insertions(+), 12 deletions(-) diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig index 8d42ebc6d302..79c09d6ee466 100644 --- a/arch/sparc/Kconfig +++ b/arch/sparc/Kconfig @@ -64,6 +64,8 @@ config SPARC32 select HAVE_UID16 select HAVE_PAGE_SIZE_4KB select LOCK_MM_AND_FIND_VMA + select MMU_GATHER_RCU_TABLE_FREE + select HAVE_ARCH_TLB_REMOVE_TABLE select OLD_SIGACTION select ZONE_DMA =20 diff --git a/arch/sparc/include/asm/pgalloc_32.h b/arch/sparc/include/asm/p= galloc_32.h index 4f73e87b22a3..36010852ba0c 100644 --- a/arch/sparc/include/asm/pgalloc_32.h +++ b/arch/sparc/include/asm/pgalloc_32.h @@ -48,7 +48,9 @@ static inline void free_pmd_fast(pmd_t * pmd) } =20 #define pmd_free(mm, pmd) free_pmd_fast(pmd) -#define __pmd_free_tlb(tlb, pmd, addr) pmd_free((tlb)->mm, pmd) + +#define __pmd_free_tlb(tlb, pmd, addr) \ + tlb_remove_table((tlb), (void *)((unsigned long)(pmd) | 1UL)) =20 #define pmd_populate(mm, pmd, pte) pmd_set(pmd, pte) =20 @@ -72,6 +74,7 @@ static inline void free_pte_fast(pte_t *pte) #define pte_free_kernel(mm, pte) free_pte_fast(pte) =20 void pte_free(struct mm_struct * mm, pgtable_t pte); -#define __pte_free_tlb(tlb, pte, addr) pte_free((tlb)->mm, pte) +void __tlb_remove_table(void *table); +#define __pte_free_tlb(tlb, pte, addr) tlb_remove_table((tlb), (void *)(pt= e)) =20 #endif /* _SPARC_PGALLOC_H */ diff --git a/arch/sparc/lib/bitext.c b/arch/sparc/lib/bitext.c index 32a5c1d9459c..c309e27973ce 100644 --- a/arch/sparc/lib/bitext.c +++ b/arch/sparc/lib/bitext.c @@ -22,8 +22,6 @@ * @align: requested alignment * * Returns offset in the map or -1 if out of space. - * - * Not safe to call from an interrupt (uses spin_lock). */ int bit_map_string_get(struct bit_map *t, int len, int align) { @@ -31,6 +29,7 @@ int bit_map_string_get(struct bit_map *t, int len, int al= ign) int off_new; int align1; int i, color; + unsigned long flags; =20 if (t->num_colors) { /* align is overloaded to be the page color */ @@ -50,7 +49,7 @@ int bit_map_string_get(struct bit_map *t, int len, int al= ign) BUG(); color &=3D align1; =20 - spin_lock(&t->lock); + spin_lock_irqsave(&t->lock, flags); if (len < t->last_size) offset =3D t->first_free; else @@ -64,7 +63,7 @@ int bit_map_string_get(struct bit_map *t, int len, int al= ign) if (offset >=3D t->size) offset =3D 0; if (count + len > t->size) { - spin_unlock(&t->lock); + spin_unlock_irqrestore(&t->lock, flags); /* P3 */ printk(KERN_ERR "bitmap out: size %d used %d off %d len %d align %d count %d\n", t->size, t->used, offset, len, align, count); @@ -90,7 +89,7 @@ int bit_map_string_get(struct bit_map *t, int len, int al= ign) t->last_off =3D 0; t->used +=3D len; t->last_size =3D len; - spin_unlock(&t->lock); + spin_unlock_irqrestore(&t->lock, flags); return offset; } } @@ -103,10 +102,11 @@ int bit_map_string_get(struct bit_map *t, int len, in= t align) void bit_map_clear(struct bit_map *t, int offset, int len) { int i; + unsigned long flags; =20 if (t->used < len) BUG(); /* Much too late to do any good, but alas... */ - spin_lock(&t->lock); + spin_lock_irqsave(&t->lock, flags); for (i =3D 0; i < len; i++) { if (test_bit(offset + i, t->map) =3D=3D 0) BUG(); @@ -115,7 +115,7 @@ void bit_map_clear(struct bit_map *t, int offset, int l= en) if (offset < t->first_free) t->first_free =3D offset; t->used -=3D len; - spin_unlock(&t->lock); + spin_unlock_irqrestore(&t->lock, flags); } =20 void bit_map_init(struct bit_map *t, unsigned long *map, int size) diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c index 9a74902ad181..2a2c7bd21011 100644 --- a/arch/sparc/mm/srmmu.c +++ b/arch/sparc/mm/srmmu.c @@ -359,19 +359,39 @@ pgtable_t pte_alloc_one(struct mm_struct *mm) return ptep; } =20 -void pte_free(struct mm_struct *mm, pgtable_t ptep) +static void __pte_free(struct mm_struct *mm, pgtable_t ptep) { + const bool process_context =3D mm; struct page *page; =20 page =3D pfn_to_page(__nocache_pa((unsigned long)ptep) >> PAGE_SHIFT); - spin_lock(&mm->page_table_lock); + if (process_context) + spin_lock(&mm->page_table_lock); if (page_ref_dec_return(page) =3D=3D 1) pagetable_dtor(page_ptdesc(page)); - spin_unlock(&mm->page_table_lock); + if (process_context) + spin_unlock(&mm->page_table_lock); =20 srmmu_free_nocache(ptep, SRMMU_PTE_TABLE_SIZE); } =20 +void pte_free(struct mm_struct *mm, pgtable_t ptep) +{ + __pte_free(mm, ptep); +} + +void __tlb_remove_table(void *table) +{ + const unsigned long encoded =3D (unsigned long)table; + const unsigned long addr =3D encoded & ~1UL; + const bool is_pmd =3D encoded & 1; + + if (is_pmd) + free_pmd_fast((pmd_t *)addr); + else /* Called from softirq context, no mm. */ + __pte_free(NULL, (pgtable_t)addr); +} + /* context handling - a dynamically sized pool is used */ #define NO_CONTEXT -1 =20 --=20 2.55.0 From nobody Sat Sep 26 13:09:29 2026 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 6CEEC37E5DC; Tue, 1 Sep 2026 11:08:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal: i=1; 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Tue, 1 Sep 2026 11:07:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788260881; bh=NMX38MYmgxlvAToP1DHMA2vWD+xtUol+ec/evF2o3L8=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=Swfsf3cC/XuFZvdPGgRF/W/c5UWYWMPj0gtiGV7TiKScdgg5EXHUHSs99MDtJbYGg xNb0iuZpwFb09zeHGZ1bBdfdnldj5Qgf4T+OHpIecErMBk7nxI967IPhhxhHVqPHJu v2ALml0CJTAPPsyF2lAQfolUcmA/hAr6eBlefyOVewtqTMQ/pgoIkGuwzs6uAMnoXw MdpgnqVWpK3wfKVFo2haXmmPm7k4thwlf5xS1BAaw1vx3plvpLkPSsJ10ENGcsj23f G6sXdLv/SRpuN9qo6X3IPSUa65grb3F7lZDAVk9FYNQwx0Gca2kihDPnu3ycbWXT8w zbyrUKUduM/dw== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 12:01:31 +0100 Subject: [PATCH 11/12] mm: make userland page table freeing RCU-safe 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: quoted-printable Message-Id: <20260901-rcu-pagetable-freeing-v1-11-5456a81c8212@kernel.org> References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> In-Reply-To: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@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 , Yoshinori Sato , 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 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 , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=20478; i=ljs@kernel.org; h=from:subject:message-id; bh=hpYZZjK8Kru66EabPGJs0LWUfMak8PU3gJpjrg3SKFk=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmbfQo57t3XO8098cV1y8677N9G5F6/zlveuOsggctT T/5ZCZJdJSyMIhxMciKKbI8/yK+P0gkbF7nBX83mDmsTCBDGLg4BWAiF7wY/lfKf7l52vp0p0Ih z5PwyO7G1LVm+4PXCGuYfnwzTbqON5Hhf5B05vcujdlnZk41tlay9tQU/Z13IiAmn0X97Oe37jX uTAA= X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Now every architecture has been converted to support CONFIG_MMU_GATHER_RCU_TABLE_FREE, this configuration option no longer makes any sense to keep around. Therefore remove it, and remove all the dead code that existed for !CONFIG_MMU_GATHER_RCU_TABLE_FREE architectures previously. Additionally, CONFIG_MMU_GATHER_TABLE_FREE is no longer necessary, as all architectures instead use CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE when a custom __tlb_remove_table() is required, so remove this too. A number of architectures only enabled CONFIG_MMU_GATHER_RCU_TABLE_FREE if CONFIG_MMU was set, however the mmu_gather logic only actually does something meaningful if CONFIG_MMU is set (mmu_gather.c is only compiled in this case, for instance). As a result, there's no need to gate any of this logic on CONFIG_MMU explicitly. CONFIG_PT_RECLAIM however does have a strict dependency on CONFIG_MMU, so make this dependency explicit. Additionally, correct comments to remove references to non-RCU page table gathering and make it clear that this is not 'semi-RCU', nor has it been since commit 1fb3d8c20bfa ("mm/mmu_gather: replace IPI with synchronize_rcu() when batch allocation fails"). With this change in place the kernel policy is now that all page tables are freed after an RCU grace period, and thus it is now safe to unconditionally perform page table walks under RCU, safe in the knowledge that page tables will not be freed underneath the walker. This is all that is guaranteed, however, so naturally it is still incumbent upon page table walkers to ensure that the page table entries are as expected. Signed-off-by: Lorenzo Stoakes (ARM) --- arch/Kconfig | 8 ----- arch/alpha/Kconfig | 1 - arch/arc/Kconfig | 1 - arch/arm/Kconfig | 1 - arch/arm64/Kconfig | 1 - arch/csky/Kconfig | 1 - arch/hexagon/Kconfig | 1 - arch/loongarch/Kconfig | 1 - arch/m68k/Kconfig | 1 - arch/microblaze/Kconfig | 1 - arch/mips/Kconfig | 1 - arch/nios2/Kconfig | 1 - arch/openrisc/Kconfig | 1 - arch/parisc/Kconfig | 1 - arch/powerpc/Kconfig | 1 - arch/riscv/Kconfig | 1 - arch/s390/Kconfig | 1 - arch/sh/Kconfig | 1 - arch/sparc/Kconfig | 2 -- arch/sparc/include/asm/tlb_64.h | 2 -- arch/um/Kconfig | 1 - arch/x86/Kconfig | 1 - arch/xtensa/Kconfig | 1 - include/asm-generic/tlb.h | 66 ++++++-------------------------------= ---- mm/Kconfig | 2 +- mm/gup.c | 5 ++-- mm/mmu_gather.c | 30 ++++--------------- 27 files changed, 18 insertions(+), 117 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 45c657772362..6f7516916797 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -526,13 +526,6 @@ config HAVE_ARCH_JUMP_LABEL config HAVE_ARCH_JUMP_LABEL_RELATIVE bool =20 -config MMU_GATHER_TABLE_FREE - bool - -config MMU_GATHER_RCU_TABLE_FREE - bool - select MMU_GATHER_TABLE_FREE - config MMU_GATHER_PAGE_SIZE bool =20 @@ -548,7 +541,6 @@ config MMU_GATHER_MERGE_VMAS =20 config MMU_GATHER_NO_GATHER bool - depends on MMU_GATHER_TABLE_FREE =20 config ARCH_WANT_IRQS_OFF_ACTIVATE_MM bool diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig index e53ef2d88463..9063c7bda4e4 100644 --- a/arch/alpha/Kconfig +++ b/arch/alpha/Kconfig @@ -42,7 +42,6 @@ config ALPHA select ARCH_STACKWALK select CPU_NO_EFFICIENT_FFS if !ALPHA_EV67 select MMU_GATHER_NO_RANGE - select MMU_GATHER_RCU_TABLE_FREE select SPARSEMEM_EXTREME if SPARSEMEM select ZONE_DMA select TRACE_IRQFLAGS_SUPPORT diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig index 7a7542b61823..2ed7186c81c5 100644 --- a/arch/arc/Kconfig +++ b/arch/arc/Kconfig @@ -47,7 +47,6 @@ config ARC select HAVE_SYSCALL_TRACEPOINTS select IRQ_DOMAIN select LOCK_MM_AND_FIND_VMA - select MMU_GATHER_RCU_TABLE_FREE select MODULES_USE_ELF_RELA select OF select OF_EARLY_FLATTREE diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 72b9afc6ae10..0cc289a7184a 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -134,7 +134,6 @@ 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 MMU select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RSEQ select HAVE_RUST if CPU_LITTLE_ENDIAN && CPU_32v7 && !KASAN diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 2bbeded33da0..b6c2dd8b2612 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -221,7 +221,6 @@ config ARM64 select HAVE_RELIABLE_STACKTRACE select HAVE_POSIX_CPU_TIMERS_TASK_WORK select HAVE_FUNCTION_ARG_ACCESS_API - select MMU_GATHER_RCU_TABLE_FREE select HAVE_RSEQ select HAVE_RUST if RUSTC_SUPPORTS_ARM64 select HAVE_STACKPROTECTOR diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig index 80f89ef1d962..4331313a42ff 100644 --- a/arch/csky/Kconfig +++ b/arch/csky/Kconfig @@ -96,7 +96,6 @@ config CSKY select HAVE_SYSCALL_TRACEPOINTS select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU select LOCK_MM_AND_FIND_VMA - select MMU_GATHER_RCU_TABLE_FREE select MAY_HAVE_SPARSE_IRQ select MODULES_USE_ELF_RELA if MODULES select OF diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig index d9b3fb86556b..b48491140013 100644 --- a/arch/hexagon/Kconfig +++ b/arch/hexagon/Kconfig @@ -23,7 +23,6 @@ config HEXAGON # select HAVE_CLK select GENERIC_ATOMIC64 select HAVE_PERF_EVENTS - select MMU_GATHER_RCU_TABLE_FREE # GENERIC_ALLOCATOR is used by dma_alloc_coherent() select GENERIC_ALLOCATOR select GENERIC_IRQ_PROBE diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig index 9c5def706222..d1b23da40737 100644 --- a/arch/loongarch/Kconfig +++ b/arch/loongarch/Kconfig @@ -188,7 +188,6 @@ config LOONGARCH select IRQ_LOONGARCH_CPU select LOCK_MM_AND_FIND_VMA select MMU_GATHER_MERGE_VMAS if MMU - select MMU_GATHER_RCU_TABLE_FREE select MODULES_USE_ELF_RELA if MODULES select NEED_PER_CPU_EMBED_FIRST_CHUNK select NEED_PER_CPU_PAGE_FIRST_CHUNK diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig index fa5d39549da9..eb84c3af92c0 100644 --- a/arch/m68k/Kconfig +++ b/arch/m68k/Kconfig @@ -37,7 +37,6 @@ config M68K select HAVE_MOD_ARCH_SPECIFIC select HAVE_UID16 select MMU_GATHER_NO_RANGE if MMU - select MMU_GATHER_RCU_TABLE_FREE if MMU select MODULES_USE_ELF_REL select MODULES_USE_ELF_RELA select NO_DMA if !MMU && !COLDFIRE diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig index af7e821e96c1..484ebb3baedf 100644 --- a/arch/microblaze/Kconfig +++ b/arch/microblaze/Kconfig @@ -41,7 +41,6 @@ config MICROBLAZE select PCI_SYSCALL if PCI select CPU_NO_EFFICIENT_FFS select MMU_GATHER_NO_RANGE - select MMU_GATHER_RCU_TABLE_FREE select SPARSE_IRQ select ZONE_DMA select TRACE_IRQFLAGS_SUPPORT diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index e2eb9627bd14..f0c43d118ca0 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -97,7 +97,6 @@ config MIPS select IRQ_FORCED_THREADING select ISA if EISA select LOCK_MM_AND_FIND_VMA - select MMU_GATHER_RCU_TABLE_FREE select MODULES_USE_ELF_REL if MODULES select MODULES_USE_ELF_RELA if MODULES && 64BIT select PERF_USE_VMALLOC diff --git a/arch/nios2/Kconfig b/arch/nios2/Kconfig index b0ccfc3b7a7e..9c0e6eaeb005 100644 --- a/arch/nios2/Kconfig +++ b/arch/nios2/Kconfig @@ -19,7 +19,6 @@ config NIOS2 select HAVE_PAGE_SIZE_4KB select IRQ_DOMAIN select LOCK_MM_AND_FIND_VMA - select MMU_GATHER_RCU_TABLE_FREE select MODULES_USE_ELF_RELA select OF select OF_EARLY_FLATTREE diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig index d90b24dd3bce..5eb995c13074 100644 --- a/arch/openrisc/Kconfig +++ b/arch/openrisc/Kconfig @@ -35,7 +35,6 @@ config OPENRISC select GENERIC_ATOMIC64 select GENERIC_CLOCKEVENTS_BROADCAST select GENERIC_SMP_IDLE_THREAD - select MMU_GATHER_RCU_TABLE_FREE select MODULES_USE_ELF_RELA select HAVE_DEBUG_STACKOVERFLOW select OR1K_PIC diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig index d3afac2f0d9b..77f67028ad89 100644 --- a/arch/parisc/Kconfig +++ b/arch/parisc/Kconfig @@ -80,7 +80,6 @@ config PARISC select GENERIC_CLOCKEVENTS select CPU_NO_EFFICIENT_FFS select THREAD_INFO_IN_TASK - select MMU_GATHER_RCU_TABLE_FREE select NEED_DMA_MAP_STATE select NEED_SG_DMA_LENGTH select HAVE_ARCH_KGDB diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 2580e27e4328..0767cfcbaa42 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -307,7 +307,6 @@ config PPC select KASAN_VMALLOC if KASAN && EXECMEM select LOCK_MM_AND_FIND_VMA select MMU_GATHER_PAGE_SIZE - select MMU_GATHER_RCU_TABLE_FREE select HAVE_ARCH_TLB_REMOVE_TABLE select MMU_GATHER_MERGE_VMAS select MMU_LAZY_TLB_SHOOTDOWN if PPC_BOOK3S_64 diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 3529ed1861ce..7741a4287498 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -208,7 +208,6 @@ config RISCV select IRQ_FORCED_THREADING select KASAN_VMALLOC if KASAN select LOCK_MM_AND_FIND_VMA - select MMU_GATHER_RCU_TABLE_FREE if MMU select MODULES_USE_ELF_RELA if MODULES select OF select OF_EARLY_FLATTREE diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index b88b85042136..a34376c05f6e 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -267,7 +267,6 @@ config S390 select LOCK_MM_AND_FIND_VMA select MMU_GATHER_MERGE_VMAS select MMU_GATHER_NO_GATHER - select MMU_GATHER_RCU_TABLE_FREE select MODULES_USE_ELF_RELA select NEED_DMA_MAP_STATE if PCI select NEED_PER_CPU_EMBED_FIRST_CHUNK diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig index 75236bef6f16..fe859def918c 100644 --- a/arch/sh/Kconfig +++ b/arch/sh/Kconfig @@ -62,7 +62,6 @@ config SUPERH select HAVE_SYSCALL_TRACEPOINTS select IRQ_FORCED_THREADING select LOCK_MM_AND_FIND_VMA - select MMU_GATHER_RCU_TABLE_FREE if MMU select MODULES_USE_ELF_RELA select NEED_SG_DMA_LENGTH select NO_DMA if !MMU && !DMA_COHERENT diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig index 79c09d6ee466..742ffff8c37f 100644 --- a/arch/sparc/Kconfig +++ b/arch/sparc/Kconfig @@ -64,7 +64,6 @@ config SPARC32 select HAVE_UID16 select HAVE_PAGE_SIZE_4KB select LOCK_MM_AND_FIND_VMA - select MMU_GATHER_RCU_TABLE_FREE select HAVE_ARCH_TLB_REMOVE_TABLE select OLD_SIGACTION select ZONE_DMA @@ -77,7 +76,6 @@ config SPARC64 select HAVE_FUNCTION_GRAPH_TRACER select HAVE_KRETPROBES select HAVE_KPROBES - select MMU_GATHER_RCU_TABLE_FREE select HAVE_ARCH_TLB_REMOVE_TABLE select MMU_GATHER_MERGE_VMAS select MMU_GATHER_NO_FLUSH_CACHE diff --git a/arch/sparc/include/asm/tlb_64.h b/arch/sparc/include/asm/tlb_6= 4.h index 3037187482db..f5f9631685d5 100644 --- a/arch/sparc/include/asm/tlb_64.h +++ b/arch/sparc/include/asm/tlb_64.h @@ -29,9 +29,7 @@ void flush_tlb_pending(void); * and therefore we don't need a TLBI when freeing page-table pages. */ =20 -#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE #define tlb_needs_table_invalidate() (false) -#endif =20 #include =20 diff --git a/arch/um/Kconfig b/arch/um/Kconfig index d9541d13d9eb..94b8ff70f578 100644 --- a/arch/um/Kconfig +++ b/arch/um/Kconfig @@ -44,7 +44,6 @@ config UML select HAVE_SYSCALL_TRACEPOINTS select THREAD_INFO_IN_TASK select SPARSE_IRQ - select MMU_GATHER_RCU_TABLE_FREE =20 config MMU bool diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index a8c3b3d31a27..6e5e462ec059 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -283,7 +283,6 @@ config X86 select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP select ASYNC_KERNEL_PGTABLE_FREE if IOMMU_SVA - select MMU_GATHER_RCU_TABLE_FREE select MMU_GATHER_MERGE_VMAS select HAVE_POSIX_CPU_TIMERS_TASK_WORK select HAVE_REGS_AND_STACK_ACCESS_API diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig index 33c4caee30e2..f2f9cd9cde50 100644 --- a/arch/xtensa/Kconfig +++ b/arch/xtensa/Kconfig @@ -55,7 +55,6 @@ config XTENSA select HAVE_VIRT_CPU_ACCOUNTING_GEN select IRQ_DOMAIN select LOCK_MM_AND_FIND_VMA - select MMU_GATHER_RCU_TABLE_FREE if MMU select MODULES_USE_ELF_RELA select PERF_USE_VMALLOC select TRACE_IRQFLAGS_SUPPORT diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h index bdcc2778ac64..044dabc1fe9c 100644 --- a/include/asm-generic/tlb.h +++ b/include/asm-generic/tlb.h @@ -67,11 +67,8 @@ * - tlb_remove_table() * * tlb_remove_table() is the basic primitive to free page-table directo= ries - * (__p*_free_tlb()). In it's most primitive form it is an alias for - * tlb_remove_page() below, for when page directories are pages and hav= e no - * additional constraints. - * - * See also MMU_GATHER_TABLE_FREE and MMU_GATHER_RCU_TABLE_FREE. + * (__p*_free_tlb()). Page directories are freed after an RCU grace + * period - see the comment in mm/mmu_gather.c. * * - tlb_remove_page() / tlb_remove_page_size() * - __tlb_remove_folio_pages() / __tlb_remove_page_size() @@ -151,24 +148,15 @@ * This might be useful if your architecture has size specific TLB * invalidation instructions. * - * MMU_GATHER_TABLE_FREE - * - * This provides tlb_remove_table(), to be used instead of tlb_remove_pag= e() - * for page directores (__p*_free_tlb()). - * - * Useful if your architecture has non-page page directories. + * Page directories (__p*_free_tlb()) are always freed via tlb_remove_tab= le(), + * after an RCU grace period (see mm/mmu_gather.c). * - * When used, an architecture is expected to provide __tlb_remove_table()= or - * use the generic __tlb_remove_table(), which does the actual freeing of= these - * pages. + * This serialises against software page-table walkers, including architec= tures + * which do not use IPIs for remote TLB invalidates. * - * MMU_GATHER_RCU_TABLE_FREE - * - * Like MMU_GATHER_TABLE_FREE, and adds semi-RCU semantics to the free (s= ee - * comment below). - * - * Useful if your architecture doesn't use IPIs for remote TLB invalidates - * and therefore doesn't naturally serialize with software page-table wal= kers. + * An architecture is expected to provide __tlb_remove_table() (see + * HAVE_ARCH_TLB_REMOVE_TABLE) or use the generic __tlb_remove_table(), w= hich + * does the actual freeing of these pages. * * MMU_GATHER_NO_FLUSH_CACHE * @@ -200,12 +188,8 @@ * various ptep_get_and_clear() functions. */ =20 -#ifdef CONFIG_MMU_GATHER_TABLE_FREE - struct mmu_table_batch { -#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE struct rcu_head rcu; -#endif unsigned int nr; void *tables[]; }; @@ -224,23 +208,6 @@ static inline void __tlb_remove_table(void *table) =20 extern void tlb_remove_table(struct mmu_gather *tlb, void *table); =20 -#else /* !CONFIG_MMU_GATHER_TABLE_FREE */ - -static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *pa= ge); -/* - * Without MMU_GATHER_TABLE_FREE the architecture is assumed to have page = based - * page directories and we can use the normal page batching to free them. - */ -static inline void tlb_remove_table(struct mmu_gather *tlb, void *table) -{ - struct ptdesc *ptdesc =3D (struct ptdesc *)table; - - pagetable_dtor(ptdesc); - tlb_remove_page(tlb, ptdesc_page(ptdesc)); -} -#endif /* CONFIG_MMU_GATHER_TABLE_FREE */ - -#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE /* * This allows an architecture that does not use the linux page-tables for * hardware to skip the TLBI when freeing page tables. @@ -253,19 +220,6 @@ void tlb_remove_table_sync_one(void); =20 void tlb_remove_table_sync_rcu(void); =20 -#else - -#ifdef tlb_needs_table_invalidate -#error tlb_needs_table_invalidate() requires MMU_GATHER_RCU_TABLE_FREE -#endif - -static inline void tlb_remove_table_sync_one(void) { } - -static inline void tlb_remove_table_sync_rcu(void) { } - -#endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */ - - #ifndef CONFIG_MMU_GATHER_NO_GATHER /* * If we can't allocate a page to make a big batch of page pointers @@ -325,9 +279,7 @@ static inline void tlb_flush_rmaps(struct mmu_gather *t= lb, struct vm_area_struct struct mmu_gather { struct mm_struct *mm; =20 -#ifdef CONFIG_MMU_GATHER_TABLE_FREE struct mmu_table_batch *batch; -#endif =20 unsigned long start; unsigned long end; diff --git a/mm/Kconfig b/mm/Kconfig index c1ddf59c0d71..bc7befafb47b 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -1465,7 +1465,7 @@ config HAVE_ARCH_TLB_REMOVE_TABLE =20 config PT_RECLAIM def_bool y - depends on MMU_GATHER_RCU_TABLE_FREE && !HAVE_ARCH_TLB_REMOVE_TABLE + depends on MMU && !HAVE_ARCH_TLB_REMOVE_TABLE help Try to reclaim empty user page table pages in paths other than munmap and exit_mmap path. diff --git a/mm/gup.c b/mm/gup.c index eb898ea1ee22..63b435ec605c 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2700,8 +2700,9 @@ EXPORT_SYMBOL(get_user_pages_unlocked); * Before activating this code, please be aware that the following assumpt= ions * are currently made: * - * *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table()= is used to - * free pages containing page tables or TLB flushing requires IPI broadca= st. + * *) tlb_remove_table() is used to free pages containing page tables, wi= th + * the free deferred until an RCU grace period has elapsed (see + * mm/mmu_gather.c). * * *) ptes can be read atomically by the architecture. * diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c index 3985d856de7f..2a72a9686773 100644 --- a/mm/mmu_gather.c +++ b/mm/mmu_gather.c @@ -218,8 +218,6 @@ bool __tlb_remove_page_size(struct mmu_gather *tlb, str= uct page *page, int page_ =20 #endif /* MMU_GATHER_NO_GATHER */ =20 -#ifdef CONFIG_MMU_GATHER_TABLE_FREE - static void __tlb_remove_table_free(struct mmu_table_batch *batch) { int i; @@ -230,10 +228,8 @@ static void __tlb_remove_table_free(struct mmu_table_b= atch *batch) free_page((unsigned long)batch); } =20 -#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE - /* - * Semi RCU freeing of the page directories. + * RCU freeing of the page directories. * * This is needed by some architectures to implement software pagetable wa= lkers. * @@ -259,13 +255,13 @@ static void __tlb_remove_table_free(struct mmu_table_= batch *batch) * means. * * What we do is batch the freed directory pages (tables) and RCU free the= m. - * We use the sched RCU variant, as that guarantees that IRQ/preempt disab= ling - * holds off grace periods. + * Disabling IRQs or preemption holds off RCU grace periods, so this prote= cts + * both rcu_read_lock() and IRQ-disabling walkers. * * However, in order to batch these pages we need to allocate storage, this * allocation is deep inside the MM code and can thus easily fail on memory - * pressure. To guarantee progress we fall back to single table freeing, s= ee - * the implementation of tlb_remove_table_one(). + * pressure. To guarantee progress we fall back to single table freeing, w= hich + * is also RCU-deferred - see the implementation of tlb_remove_table_one(). * */ =20 @@ -315,15 +311,6 @@ void tlb_remove_table_sync_rcu(void) synchronize_rcu(); } =20 -#else /* !CONFIG_MMU_GATHER_RCU_TABLE_FREE */ - -static void tlb_remove_table_free(struct mmu_table_batch *batch) -{ - __tlb_remove_table_free(batch); -} - -#endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */ - /* * If we want tlb_remove_table() to imply TLB invalidates. */ @@ -403,13 +390,6 @@ static inline void tlb_table_init(struct mmu_gather *t= lb) tlb->batch =3D NULL; } =20 -#else /* !CONFIG_MMU_GATHER_TABLE_FREE */ - -static inline void tlb_table_flush(struct mmu_gather *tlb) { } -static inline void tlb_table_init(struct mmu_gather *tlb) { } - -#endif /* CONFIG_MMU_GATHER_TABLE_FREE */ - static void tlb_flush_mmu_free(struct mmu_gather *tlb) { tlb_table_flush(tlb); --=20 2.55.0 From nobody Sat Sep 26 13:09:29 2026 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 88E0630D419; Tue, 1 Sep 2026 11:08:16 +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=1788260897; cv=none; b=PqN7+g/3ui+naQFrKIEA/RJNicpB0WjigLSUZ0iQAEfzX0q8WSXN1SJ7VGZ3XYncH6hdBizwdh2cbAfnoeR3PvxtnOFoVmZSSQIH9KWDHn015bKLPxDoJ1urtINJKiv6N8EexcwOZFc1KiaSeqWGa6wiWp4lZM8wdXN3kYUQA14= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788260897; c=relaxed/simple; bh=uhyIEUfivUfYjY2KJIFLWdl2/R/JGZ4vd0KXQY3X22M=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=FQI8TVla+usqxNnAq0tHtQO9fAUWiJTTEf6cE+H9Q/G6usRV983Lz1kC2yMWfY9jlJWSu9RBZYQWMEmw5cbvCaoGqpqiPPAZp/q40vS58GyconLCcz2d7GfjZNcUaYiQqdTJGegRUmMKBi/hKQIvBd0wBTzQ+YLnjM/loS3ySS4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PaXuseNN; 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="PaXuseNN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 65B951F01560; Tue, 1 Sep 2026 11:08:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788260896; bh=IYLKfJh2aq/+D/f0z0lQwToXfU+mbL6v7Z2WXfVA1J8=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=PaXuseNNd5OHIcETkIN99VBVpzIEgqH1cFw48vxykM+4JiQdBrwoGrZqn31H9tCrQ +nMJDRRimnHfkJ2P9tABG1G1oNyVlh0yqdetdxb7iObdNy6ZrB5/4Mx4L5cYSm53a8 y3hIIhtQV/E19hIKPtHb6XlOxhi18TzVFZVVG9Q7YGx0UoiWFAwmN0QdkEXNz28CPn /ZQxjuKaJwIMV8afJ8mHYXvZXkuP+nj2iKEeB3qvUqVOSWAgGky8z0ZIqw2++twf+o Wo7KSZR9k7YwawPyIjG6hJpogtaSBDNjiCnKJAuOaC6/0F7wqmkJMr38aIk5TyiURR c5W+esEaI4kqg== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 12:01:32 +0100 Subject: [PATCH 12/12] mm: change the contract for free_pgtables(), update docs 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: quoted-printable Message-Id: <20260901-rcu-pagetable-freeing-v1-12-5456a81c8212@kernel.org> References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> In-Reply-To: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@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 , Yoshinori Sato , 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. 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Peter Anvin" , Arnd Bergmann , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jason Gunthorpe , John Hubbard , Peter Xu 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 , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=3252; i=ljs@kernel.org; h=from:subject:message-id; bh=uhyIEUfivUfYjY2KJIFLWdl2/R/JGZ4vd0KXQY3X22M=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmbfS4vTOF89p5geaChpS/bxx23t75UvjFyz8iuyZs/ uisO22CYUcpC4MYF4OsmCLL8y/i+4NEwuZ1XvB3g5nDygQyhIGLUwAmIprHyLA3KJPz/s/VSlsZ Xsuvm5y/NLHq1MPlNccP9Nh7b2dbtU+E4X/qmuM6jqz/bpwpnn85YKn4D/eX3nxJjxc2e6kWb39 a/oELAA== X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Now that page tables are freed after an RCU grace period, it is safe for page table walkers to walk page table ranges that are being concurrently torn down, provided the mm is kept alive via mmgrab(). The comment block before pte_offset_map_lock() established a contract that this was unsafe, which was correct prior to these changes. Update it to reflect the change. Similarly update the process addresses documentation. Signed-off-by: Lorenzo Stoakes (ARM) --- Documentation/mm/process_addrs.rst | 6 ++++++ mm/pgtable-generic.c | 18 +++++++++++++++--- 2 files changed, 21 insertions(+), 3 deletions(-) diff --git a/Documentation/mm/process_addrs.rst b/Documentation/mm/process_= addrs.rst index a7296f251799..1e65b139f355 100644 --- a/Documentation/mm/process_addrs.rst +++ b/Documentation/mm/process_addrs.rst @@ -537,6 +537,12 @@ We establish basic locking rules when interacting with= page tables: * When changing a page table entry the page table lock for that page table **must** be held, except if you can safely assume nobody can access the = page tables concurrently (such as on invocation of :c:func:`!free_pgtables`). +* Page tables may be *walked* under RCU alone, as page tables are freed on= ly + after an RCU grace period has elapsed. However, any entry found must be + revalidated after the page table lock is taken (such as the + :c:func:`!pmd_same` recheck performed by :c:func:`!pte_offset_map_lock`) + before it is acted upon. Changing an entry always requires the page table + lock. * Reads from and writes to page table entries must be *appropriately* atomic. See the section on atomicity below for details. * Populating previously empty entries requires that the mmap or VMA locks = are diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c index b91b1a98029c..ff8ff3706485 100644 --- a/mm/pgtable-generic.c +++ b/mm/pgtable-generic.c @@ -386,9 +386,21 @@ pte_t *pte_offset_map_rw_nolock(struct mm_struct *mm, = pmd_t *pmd, * be read-only/read-write protected. * * Note that free_pgtables(), used after unmapping detached vmas, or when - * exiting the whole mm, does not take page table lock before freeing a pa= ge - * table, and may not use RCU at all: "outsiders" like khugepaged should a= void - * pte_offset_map() and co once the vma is detached from mm or mm_users is= zero. + * exiting the whole mm, does not take the page table lock before freeing a + * table. + * + * However, the PMD entry is cleared first, and the table freed only after + * an RCU grace period, so a walker that mapped the table under + * rcu_read_lock() stays safe, and the pmd_same() recheck in + * pte_offset_map_lock() detects the teardown. + * + * Therefore it is safe for "outsiders" like khugepaged to use + * pte_offset_map() and co. for VMAs that might be undergoing page table + * teardown. + * + * Note that the PGD itself is freed at mmdrop() time, not under RCU - so = the + * walker must keep the mm alive via mmgrab(). With that held, walking rem= ains + * safe even once mm_users has reached zero. */ pte_t *pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd, unsigned long addr, spinlock_t **ptlp) --=20 2.55.0