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=-17.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 F0389C433E0 for ; Fri, 8 Jan 2021 19:31:26 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 91DAF23A9B for ; Fri, 8 Jan 2021 19:31:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 91DAF23A9B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.63816.113176 (Exim 4.92) (envelope-from ) id 1kxxTg-0006IZ-Mc; Fri, 08 Jan 2021 19:31:16 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 63816.113176; Fri, 08 Jan 2021 19:31:16 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kxxTg-0006IR-JK; Fri, 08 Jan 2021 19:31:16 +0000 Received: by outflank-mailman (input) for mailman id 63816; Fri, 08 Jan 2021 19:31:15 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kxxTf-0006IG-45 for xen-devel@lists.xenproject.org; Fri, 08 Jan 2021 19:31:15 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kxxTc-0007h4-Ky; Fri, 08 Jan 2021 19:31:12 +0000 Received: from [54.239.6.186] (helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1kxxTc-0003cP-DP; Fri, 08 Jan 2021 19:31:12 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=zF29XQELzKvC6FplAuyKujlZ8n2GsUcbFbDogQphsC8=; b=m/nOmAs5CgrbEo8H1hQMtMosqN VlyxS/rVHrYgW0R5HWy4sLs50sqaYswT6UG6lS4BJF1hIsdp+rWvP35HilLpe9qwW/KgUM9f0Qom9 kjuERrkj0xwlr6a2vZ9NtfUvbue3Lvy+bSiSMHUNLzLA4dZtIl+jlQbGk6HnCmAbtEzo=; Subject: Re: [PATCH v2] xen/arm: do not read MVFR2 when is not defined To: Stefano Stabellini , xen-devel@lists.xenproject.org Cc: bertrand.marquis@arm.com, Volodymyr_Babchuk@epam.com, Stefano Stabellini References: <20210108192243.25889-1-sstabellini@kernel.org> From: Julien Grall Message-ID: <39db01ff-4e05-d8fd-5fef-3c85f4292b2f@xen.org> Date: Fri, 8 Jan 2021 19:31:10 +0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210108192243.25889-1-sstabellini@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Hi Stefano, On 08/01/2021 19:22, Stefano Stabellini wrote: > MVFR2 is not available on ARMv7. It is available on ARMv8 aarch32 and > aarch64. If Xen reads MVFR2 on ARMv7 it could crash. > > Avoid the issue by doing the following: > > - define MVFR2_MAYBE_UNDEFINED on arm32 > - if MVFR2_MAYBE_UNDEFINED, do not attempt to read MVFR2 in Xen > - keep the 3rd register_t in struct cpuinfo_arm.mvfr on arm32 so that a > guest read to the register returns '0' instead of crashing the guest. > > '0' is an appropriate value to return to the guest because it is defined > as "no support for miscellaneous features". > > Aarch64 Xen is not affected by this patch. > > Fixes: 9cfdb489af81 ("xen/arm: Add ID registers and complete cpuinfo") > Signed-off-by: Stefano Stabellini Acked-by: Julien Grall With one question below: > --- > xen/arch/arm/cpufeature.c | 2 ++ > xen/include/asm-arm/arm32/sysregs.h | 3 +++ > 2 files changed, 5 insertions(+) > > diff --git a/xen/arch/arm/cpufeature.c b/xen/arch/arm/cpufeature.c > index 1f6a85aafe..698bfa0201 100644 > --- a/xen/arch/arm/cpufeature.c > +++ b/xen/arch/arm/cpufeature.c > @@ -150,7 +150,9 @@ void identify_cpu(struct cpuinfo_arm *c) > > c->mvfr.bits[0] = READ_SYSREG(MVFR0_EL1); > c->mvfr.bits[1] = READ_SYSREG(MVFR1_EL1); > +#ifndef MVFR2_MAYBE_UNDEFINED > c->mvfr.bits[2] = READ_SYSREG(MVFR2_EL1); > +#endif Is there any guarantee that c->mvfr.bits[2] will be zeroed by default? Cheers, -- Julien Grall