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=-6.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 6F99BC67839 for ; Thu, 13 Dec 2018 09:13:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3CA8E20672 for ; Thu, 13 Dec 2018 09:13:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3CA8E20672 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-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727793AbeLMJNn (ORCPT ); Thu, 13 Dec 2018 04:13:43 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:56840 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727720AbeLMJNk (ORCPT ); Thu, 13 Dec 2018 04:13:40 -0500 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 A351580D; Thu, 13 Dec 2018 01:13:39 -0800 (PST) Received: from [10.1.197.36] (e112298-lin.cambridge.arm.com [10.1.197.36]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CFB563F6A8; Thu, 13 Dec 2018 01:13:37 -0800 (PST) Subject: Re: [PATCH 1/6] arm64: kpti: move check for non-vulnerable CPUs to a function To: Jeremy Linton , linux-arm-kernel@lists.infradead.org Cc: catalin.marinas@arm.com, will.deacon@arm.com, marc.zyngier@arm.com, suzuki.poulose@arm.com, dave.martin@arm.com, shankerd@codeaurora.org, mark.rutland@arm.com, linux-kernel@vger.kernel.org, ykaukab@suse.de References: <20181206234408.1287689-1-jeremy.linton@arm.com> <20181206234408.1287689-2-jeremy.linton@arm.com> From: Julien Thierry Message-ID: <1c6081ca-8335-759f-3f49-f8fa60b2fb90@arm.com> Date: Thu, 13 Dec 2018 09:13:36 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181206234408.1287689-2-jeremy.linton@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 06/12/2018 23:44, Jeremy Linton wrote: > From: Mian Yousaf Kaukab > > Add is_meltdown_safe() which is a whitelist of known safe cores. > > Signed-off-by: Mian Yousaf Kaukab > [Moved location of function] > Signed-off-by: Jeremy Linton > --- > arch/arm64/kernel/cpufeature.c | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index aec5ecb85737..242898395f68 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -908,8 +908,7 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope) > #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 > static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */ > > -static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > - int scope) > +static bool is_cpu_meltdown_safe(void) > { > /* List of CPUs that are not vulnerable and don't need KPTI */ > static const struct midr_range kpti_safe_list[] = { > @@ -917,6 +916,16 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN), > { /* sentinel */ } > }; > + /* Don't force KPTI for CPUs that are not vulnerable */ This is really a nit, but that comment would make more sense where is_cpu_meltdown_safe() is called since unmap_kernel_at_el0 is the one deciding whether to apply KPTI, is_cpu_meltdown_safe() just states whether the core is safe of not. Otherwise: Reviewed-by: Julien Thierry Cheers, Julien > + if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list)) > + return true; > + > + return false; > +} > + > +static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > + int scope) > +{ > char const *str = "command line option"; > > /* > @@ -940,8 +949,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) > return true; > > - /* Don't force KPTI for CPUs that are not vulnerable */ > - if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list)) > + if (is_cpu_meltdown_safe()) > return false; > > /* Defer to CPU feature registers */ > -- Julien Thierry