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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A69C5C3DA6E for ; Thu, 15 Dec 2022 11:29:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229906AbiLOL3a (ORCPT ); Thu, 15 Dec 2022 06:29:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44110 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229544AbiLOL31 (ORCPT ); Thu, 15 Dec 2022 06:29:27 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id E534B2A436; Thu, 15 Dec 2022 03:29:25 -0800 (PST) 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 E7FAD1063; Thu, 15 Dec 2022 03:30:05 -0800 (PST) Received: from [192.168.0.110] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 381573F5A1; Thu, 15 Dec 2022 03:29:22 -0800 (PST) Message-ID: Date: Thu, 15 Dec 2022 16:59:20 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: [PATCH] arm64: errata: refer to config ARM64_ERRATUM_2645198 to make workaround work Content-Language: en-US To: Will Deacon , Lukas Bulwahn Cc: Catalin Marinas , linux-arm-kernel@lists.infradead.org, kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org References: <20221215094811.23188-1-lukas.bulwahn@gmail.com> <20221215105745.GA7711@willie-the-truck> From: Anshuman Khandual In-Reply-To: <20221215105745.GA7711@willie-the-truck> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/15/22 16:27, Will Deacon wrote: > On Thu, Dec 15, 2022 at 10:48:11AM +0100, Lukas Bulwahn wrote: >> Commit 44ecda71fd8a ("arm64: errata: Workaround possible Cortex-A715 >> [ESR|FAR]_ELx corruption") implements a workaround for arm64 erratum >> 2645198. The arm64 cpucaps is called WORKAROUND_2645198; the kernel build >> configuration is called ARM64_ERRATUM_2645198. >> >> In the functions huge_ptep_modify_prot_start() and >> ptep_modify_prot_start(), the code accidently refers to the non-existing >> config CONFIG_ARM64_WORKAROUND_2645198. Note that the config name uses >> ERRATUM, not WORKAROUND. By this accidental misreference, this condition is >> always false, the branch of the workaround is not reachable and the >> workaround is effectively not implemented at all. >> >> Refer to the intended config ARM64_ERRATUM_2645198 and make the intended >> workaround effectively work. >> >> Fixes: 44ecda71fd8a ("arm64: errata: Workaround possible Cortex-A715 [ESR|FAR]_ELx corruption") >> Signed-off-by: Lukas Bulwahn >> --- >> arch/arm64/mm/hugetlbpage.c | 2 +- >> arch/arm64/mm/mmu.c | 2 +- >> 2 files changed, 2 insertions(+), 2 deletions(-) > > Thanks for the report! > >> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c >> index cd8d96e1fa1a..95364e8bdc19 100644 >> --- a/arch/arm64/mm/hugetlbpage.c >> +++ b/arch/arm64/mm/hugetlbpage.c >> @@ -562,7 +562,7 @@ bool __init arch_hugetlb_valid_size(unsigned long size) >> >> pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep) >> { >> - if (IS_ENABLED(CONFIG_ARM64_WORKAROUND_2645198) && >> + if (IS_ENABLED(CONFIG_ARM64_ERRATUM_2645198) && >> cpus_have_const_cap(ARM64_WORKAROUND_2645198)) { >> /* >> * Break-before-make (BBM) is required for all user space mappings >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >> index 12915f379c22..d77c9f56b7b4 100644 >> --- a/arch/arm64/mm/mmu.c >> +++ b/arch/arm64/mm/mmu.c >> @@ -1633,7 +1633,7 @@ early_initcall(prevent_bootmem_remove_init); >> >> pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep) >> { >> - if (IS_ENABLED(CONFIG_ARM64_WORKAROUND_2645198) && >> + if (IS_ENABLED(CONFIG_ARM64_ERRATUM_2645198) && >> cpus_have_const_cap(ARM64_WORKAROUND_2645198)) { >> /* >> * Break-before-make (BBM) is required for all user space mappings > > Grr, this bug seems to exist in all three versions of the patch reviewed on > the list, so I can only draw the conclusion that this code has never been Ohh, my bad, apologies. I did not have a real system with this erratum, although had emulated and tested this workaround path via some other debug changes (which might have just forced the first condition to always evaluate true). > tested. Consequently, I'm more inclined to _revert_ the change for now and > we can bring it back as a fix once somebody has checked that it actually > works properly. Please do not revert this change if possible.