From patchwork Tue Apr 8 09:52:20 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Brodsky X-Patchwork-Id: 14042592 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 CA349C3600C for ; Tue, 8 Apr 2025 09:54:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AAABA28000C; Tue, 8 Apr 2025 05:53:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A338F280001; Tue, 8 Apr 2025 05:53:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 920B228000C; Tue, 8 Apr 2025 05:53:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 723C0280001 for ; Tue, 8 Apr 2025 05:53:59 -0400 (EDT) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id B069E1A0A10 for ; Tue, 8 Apr 2025 09:53:59 +0000 (UTC) X-FDA: 83310415398.06.861BC58 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf05.hostedemail.com (Postfix) with ESMTP id 1FD7610000D for ; Tue, 8 Apr 2025 09:53:57 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf05.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=1744106038; 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=/xCdomzVQ9UKIUqSV0nOR1Orsi3U0kam6TrHTVmoiR4=; b=lupRO59ILO/HZI1+ZLLW7773BmaqQ0rs5/+NhW9K98SrcpOfcTrOu0nN/Oy1NkXh8LfJ7o nkfImwMurc0zqqBAInwcCu5jOl6q9pgUn+6eJm21oByA248wp6LC3I0GBXXEGSZNY222b+ MssC1+iC3B/yQPvVJT0+hqM4oC6n9ZM= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1744106038; a=rsa-sha256; cv=none; b=1sBFDXm/9a9oQUu2BmVQiOa5UR0QWpdjGr8cSYHqOCgPlkRnCmWMlWRJxJm8gDvcSw8s9o nLnz2qWME4VE/SJdwPwEUnV1lMmUfALmpi0MYNErqnceiPDCOWjX7UIpP0FQK/97NhWHk+ XZ5cwNh/ePm7erdPyteOsFgUUTuFjnY= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf05.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 5D48D16A3; Tue, 8 Apr 2025 02:53:58 -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 1DCDA3F6A8; Tue, 8 Apr 2025 02:53:52 -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, x86@kernel.org Subject: [PATCH v2 10/12] riscv: mm: Clarify ctor mm argument in alloc_{pte,pmd}_late Date: Tue, 8 Apr 2025 10:52:20 +0100 Message-ID: <20250408095222.860601-11-kevin.brodsky@arm.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20250408095222.860601-1-kevin.brodsky@arm.com> References: <20250408095222.860601-1-kevin.brodsky@arm.com> MIME-Version: 1.0 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 1FD7610000D X-Stat-Signature: tgi89zumacaswgdx8k1idezfa8j8p9ro X-Rspam-User: X-HE-Tag: 1744106037-235133 X-HE-Meta: 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 HJGVDTeJ wxSIEkyXGCYAR15nahrRj181o11L9v5sR08F75wtBdl0cnbBwpKv33WHfwxBXnXc85Jo+iAWeinKsGr3J+CXIQfdq6nw54Oq9hjkVpHeg0qgslk9X59McXFpT6uq6y2XFBVcX4dUne0OaSuc/0RR5X4wES2es2ZR3rb4T2iG1O2mI2ow7KsH0GyRLbDlPUEfMfG34+UQW0wJAukk= 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 e5ef693fc778..59a982f88908 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -442,6 +442,11 @@ 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)); } @@ -522,6 +527,7 @@ 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)); }