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 87A43C636CD for ; Wed, 1 Feb 2023 12:21:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=5BLEG88nXAgQo8zqWDVCanmHnzFtISRsJiH4w6KV6zk=; b=Kj5mbzMMIZmdSW kISGttEXEOlCBSvzgJuk8ADogW3YlVtKW5rpKGRFC7ocTUyWxbvlsK/A55p1knowBkTEc58ka1BFF D+CV1GlYgCDwhh2soBLbIWQSrqC/ujkJz0WTDgBYuaV0Mq53uEf/D4ez/Qq5iV6E487IwW+28Zcud bI+SsvUJMJzgDfRPKwKnDdIhJlUc6FyRh9458wkPzWdSV8rrRh6mKexIOScBl8YCjnfnKVc48uBJL HyeQUdzrkfu2o3emJLBoDmTpSMJ+tY2HNIipomxiq7f0yTYbK8Fcq4HBEiRrS7/ehmBOsWJmRMmeL 7zATG86FzAP4jxlJMP/Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pNC6D-00Bh8J-RK; Wed, 01 Feb 2023 12:20:25 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pNC6A-00Bh7N-6g for linux-arm-kernel@lists.infradead.org; Wed, 01 Feb 2023 12:20:24 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7D8C96177A; Wed, 1 Feb 2023 12:20:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0547CC433EF; Wed, 1 Feb 2023 12:20:18 +0000 (UTC) Date: Wed, 1 Feb 2023 12:20:16 +0000 From: Catalin Marinas To: Will Deacon Cc: Robin Murphy , Anshuman Khandual , linux-arm-kernel@lists.infradead.org, Mark Rutland , Andrew Morton , linux-kernel@vger.kernel.org, Mark Brown , Muchun Song Subject: Re: [PATCH V2] arm64/mm: Intercept pfn changes in set_pte_at() Message-ID: References: <20230109052816.405335-1-anshuman.khandual@arm.com> <20230126133321.GB29148@willie-the-truck> <20230131154950.GB2646@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20230131154950.GB2646@willie-the-truck> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230201_042022_339449_35D2A71D X-CRM114-Status: GOOD ( 26.18 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Jan 31, 2023 at 03:49:51PM +0000, Will Deacon wrote: > On Fri, Jan 27, 2023 at 12:43:17PM +0000, Robin Murphy wrote: > > On 2023-01-26 13:33, Will Deacon wrote: > > > On Tue, Jan 24, 2023 at 11:11:49AM +0530, Anshuman Khandual wrote: > > > > On 1/9/23 10:58, Anshuman Khandual wrote: > > > > > Changing pfn on a user page table mapped entry, without first going through > > > > > break-before-make (BBM) procedure is unsafe. This just updates set_pte_at() > > > > > to intercept such changes, via an updated pgattr_change_is_safe(). This new > > > > > check happens via __check_racy_pte_update(), which has now been renamed as > > > > > __check_safe_pte_update(). > > > > > > > > > > Cc: Catalin Marinas > > > > > Cc: Will Deacon > > > > > Cc: Mark Rutland > > > > > Cc: Andrew Morton > > > > > Cc: linux-arm-kernel@lists.infradead.org > > > > > Cc: linux-kernel@vger.kernel.org > > > > > Signed-off-by: Anshuman Khandual > > > > > --- > > > > > This applies on v6.2-rc3. This patch had some test time on an internal CI > > > > > system without any issues being reported. > > > > > > > > Gentle ping, any updates on this patch ? Still any concerns ? > > > > > > I don't think we really got to the bottom of Mark's concerns with > > > unreachable ptes on the stack, did we? I also have vague recollections > > > of somebody (Robin?) running into issues with the vmap code not honouring > > > BBM. > > > > Doesn't ring a bell, so either it wasn't me, or it was many years ago and > > about 5 levels deep into trying to fix something else :/ > > Bah, sorry! Catalin reckons it may have been him talking about the vmemmap. Indeed. The discussion with Anshuman started from this thread: https://lore.kernel.org/all/20221025014215.3466904-1-mawupeng1@huawei.com/ We already trip over the existing checks even without Anshuman's patch, though only by chance. We are not setting the software PTE_DIRTY on the new pte (we don't bother with this bit for kernel mappings). Given that the vmemmap ptes are still live when such change happens and no-one came with a solution to the break-before-make problem, I propose we revert the arm64 part of commit 47010c040dec ("mm: hugetlb_vmemmap: cleanup CONFIG_HUGETLB_PAGE_FREE_VMEMMAP*"). We just need this hunk: diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 27b2592698b0..5263454a5794 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -100,7 +100,6 @@ config ARM64 select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT select ARCH_WANT_FRAME_POINTERS select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36) - select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP select ARCH_WANT_LD_ORPHAN_WARN select ARCH_WANTS_NO_INSTR select ARCH_WANTS_THP_SWAP if ARM64_4K_PAGES -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel