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=-7.0 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 4AD89C4360F for ; Thu, 4 Apr 2019 16:45:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1983520693 for ; Thu, 4 Apr 2019 16:45:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729547AbfDDQpK (ORCPT ); Thu, 4 Apr 2019 12:45:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55596 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727353AbfDDQpJ (ORCPT ); Thu, 4 Apr 2019 12:45:09 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D8CB93078AAE; Thu, 4 Apr 2019 16:45:08 +0000 (UTC) Received: from treble.redhat.com (ovpn-125-158.rdu2.redhat.com [10.10.125.158]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1ED53608E5; Thu, 4 Apr 2019 16:45:06 +0000 (UTC) From: Josh Poimboeuf To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Jiri Kosina , Waiman Long , Andrea Arcangeli , Jon Masters , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , linuxppc-dev@lists.ozlabs.org, Martin Schwidefsky , Heiko Carstens , linux-s390@vger.kernel.org, Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, Greg Kroah-Hartman , Tyler Hicks , Linus Torvalds Subject: [PATCH RFC 1/5] cpu/speculation: Add 'cpu_spec_mitigations=' cmdline options Date: Thu, 4 Apr 2019 11:44:11 -0500 Message-Id: In-Reply-To: References: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.48]); Thu, 04 Apr 2019 16:45:09 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Keeping track of the number of mitigations for all the CPU speculation bugs has become overwhelming for many users. It's getting more and more complicated to decide which mitigations are needed for a given architecture. Complicating matters is the fact that each arch tends to their own custom way to mitigate the same vulnerability. Most users fall into a few basic categories: a) they want all mitigations off; b) they want all reasonable mitigations on, with SMT enabled even if it's vulnerable; or c) they want all reasonable mitigations on, with SMT disabled if vulnerable. Define a set of curated, arch-independent options, each of which is an aggregation of existing options: - cpu_spec_mitigations=off: Disable all mitigations. - cpu_spec_mitigations=auto: [default] Enable all the default mitigations, but leave SMT enabled, even if it's vulnerable. - cpu_spec_mitigations=auto,nosmt: Enable all the default mitigations, disabling SMT if needed by a mitigation. Currently, these options are placeholders which don't actually do anything. They will be fleshed out in upcoming patches. Signed-off-by: Josh Poimboeuf --- .../admin-guide/kernel-parameters.txt | 23 +++++++++++++++++++ include/linux/cpu.h | 8 +++++++ kernel/cpu.c | 15 ++++++++++++ 3 files changed, 46 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index c4d830003b21..ac42e510bd6e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2544,6 +2544,29 @@ in the "bleeding edge" mini2440 support kernel at http://repo.or.cz/w/linux-2.6/mini2440.git + cpu_spec_mitigations= + [KNL] Control mitigations for CPU speculation + vulnerabilities on affected CPUs. This is a set of + curated, arch-independent options, each of which is an + aggregation of existing options. + + off + Disable all speculative CPU mitigations. + + auto (default) + Mitigate all speculative CPU vulnerabilities, + but leave SMT enabled, even if it's vulnerable. + This is useful for users who don't want to be + surprised by SMT getting disabled across kernel + upgrades, or who have other ways of avoiding + SMT-based attacks. + + auto,nosmt + Mitigate all speculative CPU vulnerabilities, + disabling SMT if needed. This is for users who + always want to be fully mitigated, even if it + means losing SMT. + mminit_loglevel= [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this parameter allows control of the logging verbosity for diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 5041357d0297..3a1740fda2e2 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -187,4 +187,12 @@ static inline void cpu_smt_disable(bool force) { } static inline void cpu_smt_check_topology(void) { } #endif +enum cpu_spec_mitigations { + CPU_SPEC_MITIGATIONS_OFF, + CPU_SPEC_MITIGATIONS_AUTO, + CPU_SPEC_MITIGATIONS_AUTO_NOSMT, +}; + +extern enum cpu_spec_mitigations cpu_spec_mitigations; + #endif /* _LINUX_CPU_H_ */ diff --git a/kernel/cpu.c b/kernel/cpu.c index 6c959aea0f9e..0a9d66b90a00 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2306,3 +2306,18 @@ void __init boot_cpu_hotplug_init(void) #endif this_cpu_write(cpuhp_state.state, CPUHP_ONLINE); } + +enum cpu_spec_mitigations cpu_spec_mitigations __ro_after_init = CPU_SPEC_MITIGATIONS_AUTO; + +static int __init cpu_spec_mitigations_setup(char *arg) +{ + if (!strcmp(arg, "off")) + cpu_spec_mitigations = CPU_SPEC_MITIGATIONS_OFF; + else if (!strcmp(arg, "auto")) + cpu_spec_mitigations = CPU_SPEC_MITIGATIONS_AUTO; + else if (!strcmp(arg, "auto,nosmt")) + cpu_spec_mitigations = CPU_SPEC_MITIGATIONS_AUTO_NOSMT; + + return 0; +} +early_param("cpu_spec_mitigations", cpu_spec_mitigations_setup); -- 2.17.2