From mboxrd@z Thu Jan 1 00:00:00 1970 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 66B60C021B8 for ; Wed, 26 Feb 2025 08:27:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=A+fqdQWLrg7ifJX9iUDj6h0MM8pxgyoJDsCoHitt3FY=; b=aixzF5xyJ72NCpvHEM3EK53j1c IZFtYp0/P1JZJuLd2ShvX8lICA7lBmijC6NgtlxvODpr3EHa4Yeh+WjNkGKXJ5x4GZyk6KaiUXs5l bj7ePv6Qpcqy210/UB2VUYlxtWg9A1fJdWttlLPG/szArgj4Xox5lNnpgJKPtKBQ0vq5BRgDq45SW FFmxe3Jy4InS+sWfEV7iNTG1PmPaAw1zftsUgJiitz+NilzpszbjjhQgsRDWW4wPdcrQSFYk+KdiC MGOZJnl3wJEDQXmMMSxB5W3p/jiIA0yYPEpZ/SS9cyxNmuYOhqxHXzD5Z5H48BUoLw96e1k7i9GGg JfTFAz2A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tnClG-00000002sDD-0FTn; Wed, 26 Feb 2025 08:27:22 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tnCU7-00000002p26-1JAt for linux-arm-kernel@lists.infradead.org; Wed, 26 Feb 2025 08:09:40 +0000 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 7A0441516; Wed, 26 Feb 2025 00:09:54 -0800 (PST) Received: from [10.57.84.229] (unknown [10.57.84.229]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7C9B03F673; Wed, 26 Feb 2025 00:09:32 -0800 (PST) Message-ID: Date: Wed, 26 Feb 2025 08:09:32 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/4] arm64: hugetlb: Fix huge_ptep_get_and_clear() for non-present ptes Content-Language: en-GB To: Will Deacon Cc: Catalin Marinas , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Naveen N Rao , Paul Walmsley , Palmer Dabbelt , Albert Ou , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Gerald Schaefer , "David S. Miller" , Andreas Larsson , Arnd Bergmann , Muchun Song , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , David Hildenbrand , "Matthew Wilcox (Oracle)" , Mark Rutland , Anshuman Khandual , Dev Jain , Kevin Brodsky , Alexandre Ghiti , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20250217140419.1702389-1-ryan.roberts@arm.com> <20250217140419.1702389-3-ryan.roberts@arm.com> <20250221153156.GC20567@willie-the-truck> <6ebf36f2-2e55-49b2-8764-90fd972d6e66@arm.com> <20250225221812.GA23870@willie-the-truck> From: Ryan Roberts In-Reply-To: <20250225221812.GA23870@willie-the-truck> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250226_000939_443373_F2FCAC72 X-CRM114-Status: GOOD ( 14.81 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 25/02/2025 22:18, Will Deacon wrote: > On Mon, Feb 24, 2025 at 12:11:19PM +0000, Ryan Roberts wrote: >> On 21/02/2025 15:31, Will Deacon wrote: >>> On Mon, Feb 17, 2025 at 02:04:15PM +0000, Ryan Roberts wrote: >>>> + pte = __ptep_get_and_clear(mm, addr, ptep); >>>> + present = pte_present(pte); >>>> + while (--ncontig) { >>>> + ptep++; >>>> + addr += pgsize; >>>> + tmp_pte = __ptep_get_and_clear(mm, addr, ptep); >>>> + if (present) { >>>> + if (pte_dirty(tmp_pte)) >>>> + pte = pte_mkdirty(pte); >>>> + if (pte_young(tmp_pte)) >>>> + pte = pte_mkyoung(pte); >>>> + } >>>> } >>> >>> nit: With the loop now structured like this, we really can't handle >>> num_contig_ptes() returning 0 if it gets an unknown size. Granted, that >>> really shouldn't happen, but perhaps it would be better to add a 'default' >>> case with a WARN() to num_contig_ptes() and then add an early return here? >> >> Looking at other users of num_contig_ptes() it looks like huge_ptep_get() >> already assumes at least 1 pte (it calls __ptep_get() before calling >> num_contig_ptes()) and set_huge_pte_at() assumes 1 pte for the "present and >> non-contig" case. So num_contig_ptes() returning 0 is already not really >> consumed consistently. >> >> How about we change the default num_contig_ptes() return value to 1 and add a >> warning if size is invalid: > > Fine by me! > > I assume you'll fold that in and send a new version, along with the typo > fixes? Yep, I'll aim to post this today. I have a few review comments for s390 to add in too. > > Cheers, > > Will