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 X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6E7FDC282D8 for ; Wed, 30 Jan 2019 14:57:04 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 3FC3220882 for ; Wed, 30 Jan 2019 14:57:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="oD2ycSXx" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3FC3220882 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=bSTLdxO8ErF/n7/tmjN2cmnjAq6rA1YbEUNbbq9jF7A=; b=oD2ycSXx2ErviXtx05cY1kxnq MhkrSqr0nzzdVeyCeZ0drdKq1uvbEfa/PPt+uMR+y2hAY1h/7+WDMZde5x9LeAWJ6XZhhvjWFO4j1 DQdsNVAMjdnJ6YFj2AIEJeTCwdeYAFWFYBb26huePBKyV2IPV9ogJX1wJUmV7U8zq+q0rRvMe148Q dzgadf6i9mdMcKWDoDN6vgdKR9b8/nHozBrcq5ijQ87hqN1ne3Ptp8mkhW3FRDI1cxfj8SjDmeb7e em6K0E/8dmJkaXKC/EfFJ+sqOao6atNsoM9QRoo7v5ygR0Zpn3S4cJYZ8cIXo9TqNHEOWzIwZetIq wBXH9YaWQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gorIS-0002Sz-R3; Wed, 30 Jan 2019 14:57:00 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gorIP-0002SH-1i for linux-arm-kernel@lists.infradead.org; Wed, 30 Jan 2019 14:56:58 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A53B5EBD; Wed, 30 Jan 2019 06:56:55 -0800 (PST) Received: from [10.37.9.196] (unknown [10.37.9.196]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 24B3C3F589; Wed, 30 Jan 2019 06:56:53 -0800 (PST) Subject: Re: [PATCH v3 0/1] arm64: Add workaround for Fujitsu A64FX erratum 010001 To: Catalin Marinas , "Zhang, Lei" References: <8898674D84E3B24BA3A2D289B872026A6A2C04E6@G01JPEXMBKW03> <20190129181032.GC224095@arrakis.emea.arm.com> From: James Morse Message-ID: <57c09d48-2c09-f1e1-0f70-c8249bc8329f@arm.com> Date: Wed, 30 Jan 2019 14:56:52 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190129181032.GC224095@arrakis.emea.arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190130_065657_090601_6B14C3E2 X-CRM114-Status: GOOD ( 20.37 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: 'Mark Rutland' , "'will.deacon@arm.com'" , "'linux-kernel@vger.kernel.org'" , "'linux-arm-kernel@lists.infradead.org'" Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi guys, On 01/29/2019 06:10 PM, Catalin Marinas wrote: > Could you please copy the whole description from the cover letter to the > actual patch and only send one email (full description as in here > together with the patch)? If we commit this to the kernel, it would be > useful to have the information in the log for reference later on. > > More comments below: > > On Tue, Jan 29, 2019 at 12:29:58PM +0000, Zhang, Lei wrote: >> On some variants of the Fujitsu-A64FX cores ver(1.0, 1.1), >> memory accesses may cause undefined fault (Data abort, DFSC=0b111111). >> This problem will be fixed by next version of Fujitsu-A64FX. >> >> This fault occurs under a specific hardware condition >> when a load/store instruction perform an address translation using: >> case-1 TTBR0_EL1 with TCR_EL1.NFD0 == 1. >> case-2 TTBR0_EL2 with TCR_EL2.NFD0 == 1. >> case-3 TTBR1_EL1 with TCR_EL1.NFD1 == 1. >> case-4 TTBR1_EL2 with TCR_EL2.NFD1 == 1. >> And this fault occurs completely spurious. > > So this looks like new information on the hardware behaviour since the > v2 of the patch. Can this fault occur for any type of instruction > accessing the memory or only for SVE instructions? > >> Since TCR_ELx.NFD1 is set to '1' at the kernel in versions >> past 4.17, the case-3 or case-4 may happen. >> >> This fault can be taken only at stage-1, >> so this fault is taken from EL0 to EL1/EL2, from EL1 to EL1, >> or from EL2 to EL2. >> >> I would like to post a workaround to avoid this problem on >> existing Fujitsu-A64FX version. > > How likely is it to trigger this erratum? In other words, aren't we > better off with a spurious fault that we ignore rather than toggling the > TCR_ELx.NFD1 bit? It sounds like the spurious fault can occur as a result of load/store. ('there is no load/store instruction between'...). If this can happen in kernel_enter it will overwrite the exception registers, and we lose the original ELR. If load/store trigger it, I don't think we can ignore it. Thanks, James _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel