From patchwork Mon Mar 17 14:16:58 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Brodsky X-Patchwork-Id: 14019353 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 98D0CC35FF3 for ; Mon, 17 Mar 2025 14:22:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5566728000A; Mon, 17 Mar 2025 10:22:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4DDB5280001; Mon, 17 Mar 2025 10:22:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3816F28000A; Mon, 17 Mar 2025 10:22:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 197F6280001 for ; Mon, 17 Mar 2025 10:22:13 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 9FE3382011 for ; Mon, 17 Mar 2025 14:22:14 +0000 (UTC) X-FDA: 83231257788.29.9DECB00 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf17.hostedemail.com (Postfix) with ESMTP id B0DC44001A for ; Mon, 17 Mar 2025 14:22:12 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf17.hostedemail.com: domain of kevin.brodsky@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=kevin.brodsky@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1742221332; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IFWyEFvD7taIrIds3ww1RZCtlo3XiqYGCEZ44ZgHvMg=; b=nyVDlchlketc9mtrRbjcKkPoMaVTW4mGmn6zjSxT1JQKSQZkSoDKie4x4o35HFBB0IWcdX 3V62F+6OJAYHFuEL3jLGWo+EgowuPDDYd5vHaxyvkkJaojt7jEu7sb8bybfO1htKGNlhfG FPYQoXD8OlpN/yHbr+goN1i7koJWdWg= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1742221332; a=rsa-sha256; cv=none; b=sZTkBp476vpvR5A8zRqttSWZjg9nA6elrP7Hf2Ui0FicvJU4oHh5sFhR1Psk7xOuGgGRxO RBeec24ZtiJJdZlt/wYO8jkougS4zHRDmCihgGnW9n1ITkRwzlRhhSqrnKy1jC3flH77N1 aniYYzWn/yaQih3sjdeqWJLe/3HovSY= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf17.hostedemail.com: domain of kevin.brodsky@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=kevin.brodsky@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D64111688; Mon, 17 Mar 2025 07:22:20 -0700 (PDT) Received: from e123572-lin.arm.com (e123572-lin.cambridge.arm.com [10.1.194.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AEC523F63F; Mon, 17 Mar 2025 07:22:07 -0700 (PDT) From: Kevin Brodsky To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Kevin Brodsky , Albert Ou , Andreas Larsson , Andrew Morton , Catalin Marinas , Dave Hansen , "David S. Miller" , Geert Uytterhoeven , Linus Walleij , Madhavan Srinivasan , Mark Rutland , Matthew Wilcox , Michael Ellerman , "Mike Rapoport (IBM)" , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Qi Zheng , Ryan Roberts , Will Deacon , Yang Shi , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org Subject: [PATCH 09/11] riscv: mm: Clarify ctor mm argument in alloc_{pte,pmd}_late Date: Mon, 17 Mar 2025 14:16:58 +0000 Message-ID: <20250317141700.3701581-10-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20250317141700.3701581-1-kevin.brodsky@arm.com> References: <20250317141700.3701581-1-kevin.brodsky@arm.com> MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: B0DC44001A X-Stat-Signature: mnb8tduf68tg3faqaxadxh5u7tk5f7s4 X-HE-Tag: 1742221332-110409 X-HE-Meta: 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 2WueNl35 RcjHKWBZJHfVQ11j3SvNSLBQRW5oxHWvIiNLa1by9DIHyBuXeKHcWUxlWyxek9FzGwrW60/pXLDkunu3+igbQeeX0cet1AM6n2IMTjGKXT3Id9D6o1xEZ8a9GMHSFDw0yqCuxImwmdXXmo882sWKvLPVqZeMt6dDxr+UV0TBdS87w3853FU21L5m8X6CbKstZSRVV0Ji+oum9tLk= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: pagetable_{pte,pmd}_ctor(mm, ptdesc) skip the ptlock initialisation if mm is &init_mm. To avoid unnecessary overhead, it is therefore preferable to pass the actual mm associated to the PTE/PMD. Unfortunately, this proves challenging for alloc_{pte,pmd}_late() as the associated mm is not available at the point where they are called - in fact not even top-level functions like create_pgd_mapping() are passed the mm. As a result they both call the ctor with NULL as mm; this is safe but potentially wasteful. This is not a new situation, but let's add a couple of comments to clarify it. Signed-off-by: Kevin Brodsky --- arch/riscv/mm/init.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index 703c3648cfa9..fb18940113f2 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -409,6 +409,11 @@ static phys_addr_t __meminit alloc_pte_late(uintptr_t va) { struct ptdesc *ptdesc = pagetable_alloc(GFP_KERNEL & ~__GFP_HIGHMEM, 0); + /* + * We do not know which mm the PTE page is associated to at this point. + * Passing NULL to the ctor is the safe option, though it may result + * in unnecessary work (e.g. initialising the ptlock for init_mm). + */ BUG_ON(!ptdesc || !pagetable_pte_ctor(NULL, ptdesc)); return __pa((pte_t *)ptdesc_address(ptdesc)); } @@ -489,6 +494,7 @@ static phys_addr_t __meminit alloc_pmd_late(uintptr_t va) { struct ptdesc *ptdesc = pagetable_alloc(GFP_KERNEL & ~__GFP_HIGHMEM, 0); + /* See comment in alloc_pte_late() regarding NULL passed the ctor */ BUG_ON(!ptdesc || !pagetable_pmd_ctor(NULL, ptdesc)); return __pa((pmd_t *)ptdesc_address(ptdesc)); }