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=-6.4 required=3.0 tests=DATE_IN_PAST_24_48, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS 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 F237AC65BAE for ; Thu, 13 Dec 2018 16:18:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BE1AE20879 for ; Thu, 13 Dec 2018 16:18:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BE1AE20879 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 S1729385AbeLMQSN (ORCPT ); Thu, 13 Dec 2018 11:18:13 -0500 Received: from foss.arm.com ([217.140.101.70]:36900 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727428AbeLMQSN (ORCPT ); Thu, 13 Dec 2018 11:18:13 -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 A5C6280D; Thu, 13 Dec 2018 08:18:12 -0800 (PST) Received: from [192.168.100.242] (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A0E533F614; Thu, 13 Dec 2018 08:18:11 -0800 (PST) Subject: Re: [PATCH 1/6] arm64: kpti: move check for non-vulnerable CPUs to a function To: Julien Thierry , 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> <1c6081ca-8335-759f-3f49-f8fa60b2fb90@arm.com> From: Jeremy Linton Message-ID: <672f0f2f-5ebc-ea3d-d3c0-4a2dd253ae09@arm.com> Date: Wed, 12 Dec 2018 08:36:19 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <1c6081ca-8335-759f-3f49-f8fa60b2fb90@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed 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 Julien, Thanks for looking at this, On 12/13/2018 03:13 AM, Julien Thierry wrote: > 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. That is a good point, thanks. > > 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 */ >> >