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=-12.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,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 365B2C43441 for ; Wed, 28 Nov 2018 14:36:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E8E4D2081B for ; Wed, 28 Nov 2018 14:36:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E8E4D2081B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zytor.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 S1728608AbeK2Bh5 (ORCPT ); Wed, 28 Nov 2018 20:37:57 -0500 Received: from terminus.zytor.com ([198.137.202.136]:57581 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727979AbeK2Bh5 (ORCPT ); Wed, 28 Nov 2018 20:37:57 -0500 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id wASEZNTX2324449 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 28 Nov 2018 06:35:24 -0800 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id wASEZNO12324438; Wed, 28 Nov 2018 06:35:23 -0800 Date: Wed, 28 Nov 2018 06:35:23 -0800 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Thomas Gleixner Message-ID: Cc: mingo@kernel.org, peterz@infradead.org, david.c.stewart@intel.com, longman9394@gmail.com, jkosina@suse.cz, ak@linux.intel.com, casey.schaufler@intel.com, gregkh@linuxfoundation.org, arjan@linux.intel.com, jcm@redhat.com, tglx@linutronix.de, thomas.lendacky@amd.com, dave.hansen@intel.com, luto@kernel.org, hpa@zytor.com, asit.k.mallick@intel.com, jpoimboe@redhat.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, dwmw@amazon.co.uk, aarcange@redhat.com, keescook@chromium.org, tim.c.chen@linux.intel.com Reply-To: jpoimboe@redhat.com, linux-kernel@vger.kernel.org, hpa@zytor.com, asit.k.mallick@intel.com, keescook@chromium.org, tim.c.chen@linux.intel.com, dwmw@amazon.co.uk, torvalds@linux-foundation.org, aarcange@redhat.com, jcm@redhat.com, thomas.lendacky@amd.com, dave.hansen@intel.com, luto@kernel.org, tglx@linutronix.de, ak@linux.intel.com, longman9394@gmail.com, jkosina@suse.cz, gregkh@linuxfoundation.org, arjan@linux.intel.com, casey.schaufler@intel.com, mingo@kernel.org, david.c.stewart@intel.com, peterz@infradead.org In-Reply-To: <20181125185005.958421388@linutronix.de> References: <20181125185005.958421388@linutronix.de> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/pti] x86/speculation: Enable prctl mode for spectre_v2_user Git-Commit-ID: 7cc765a67d8e04ef7d772425ca5a2a1e2b894c15 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 7cc765a67d8e04ef7d772425ca5a2a1e2b894c15 Gitweb: https://git.kernel.org/tip/7cc765a67d8e04ef7d772425ca5a2a1e2b894c15 Author: Thomas Gleixner AuthorDate: Sun, 25 Nov 2018 19:33:54 +0100 Committer: Thomas Gleixner CommitDate: Wed, 28 Nov 2018 11:57:13 +0100 x86/speculation: Enable prctl mode for spectre_v2_user Now that all prerequisites are in place: - Add the prctl command line option - Default the 'auto' mode to 'prctl' - When SMT state changes, update the static key which controls the conditional STIBP evaluation on context switch. - At init update the static key which controls the conditional IBPB evaluation on context switch. Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Jiri Kosina Cc: Tom Lendacky Cc: Josh Poimboeuf Cc: Andrea Arcangeli Cc: David Woodhouse Cc: Tim Chen Cc: Andi Kleen Cc: Dave Hansen Cc: Casey Schaufler Cc: Asit Mallick Cc: Arjan van de Ven Cc: Jon Masters Cc: Waiman Long Cc: Greg KH Cc: Dave Stewart Cc: Kees Cook Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181125185005.958421388@linutronix.de --- Documentation/admin-guide/kernel-parameters.txt | 7 ++++- arch/x86/kernel/cpu/bugs.c | 41 +++++++++++++++++++------ 2 files changed, 38 insertions(+), 10 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index b6e5b33b9d75..a9b98a4e8789 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4236,9 +4236,14 @@ off - Unconditionally disable mitigations. Is enforced by spectre_v2=off + prctl - Indirect branch speculation is enabled, + but mitigation can be enabled via prctl + per thread. The mitigation control state + is inherited on fork. + auto - Kernel selects the mitigation depending on the available CPU features and vulnerability. - Default is off. + Default is prctl. Not specifying this option is equivalent to spectre_v2_user=auto. diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 74359fff87fd..d0137d10f9a6 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -255,11 +255,13 @@ enum spectre_v2_user_cmd { SPECTRE_V2_USER_CMD_NONE, SPECTRE_V2_USER_CMD_AUTO, SPECTRE_V2_USER_CMD_FORCE, + SPECTRE_V2_USER_CMD_PRCTL, }; static const char * const spectre_v2_user_strings[] = { [SPECTRE_V2_USER_NONE] = "User space: Vulnerable", [SPECTRE_V2_USER_STRICT] = "User space: Mitigation: STIBP protection", + [SPECTRE_V2_USER_PRCTL] = "User space: Mitigation: STIBP via prctl", }; static const struct { @@ -270,6 +272,7 @@ static const struct { { "auto", SPECTRE_V2_USER_CMD_AUTO, false }, { "off", SPECTRE_V2_USER_CMD_NONE, false }, { "on", SPECTRE_V2_USER_CMD_FORCE, true }, + { "prctl", SPECTRE_V2_USER_CMD_PRCTL, false }, }; static void __init spec_v2_user_print_cond(const char *reason, bool secure) @@ -324,12 +327,15 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) smt_possible = false; switch (spectre_v2_parse_user_cmdline(v2_cmd)) { - case SPECTRE_V2_USER_CMD_AUTO: case SPECTRE_V2_USER_CMD_NONE: goto set_mode; case SPECTRE_V2_USER_CMD_FORCE: mode = SPECTRE_V2_USER_STRICT; break; + case SPECTRE_V2_USER_CMD_AUTO: + case SPECTRE_V2_USER_CMD_PRCTL: + mode = SPECTRE_V2_USER_PRCTL; + break; } /* Initialize Indirect Branch Prediction Barrier */ @@ -340,6 +346,9 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) case SPECTRE_V2_USER_STRICT: static_branch_enable(&switch_mm_always_ibpb); break; + case SPECTRE_V2_USER_PRCTL: + static_branch_enable(&switch_mm_cond_ibpb); + break; default: break; } @@ -352,6 +361,12 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED) return; + /* + * If SMT is not possible or STIBP is not available clear the STIPB + * mode. + */ + if (!smt_possible || !boot_cpu_has(X86_FEATURE_STIBP)) + mode = SPECTRE_V2_USER_NONE; set_mode: spectre_v2_user = mode; /* Only print the STIBP mode when SMT possible */ @@ -552,6 +567,15 @@ static void update_stibp_strict(void) on_each_cpu(update_stibp_msr, NULL, 1); } +/* Update the static key controlling the evaluation of TIF_SPEC_IB */ +static void update_indir_branch_cond(void) +{ + if (sched_smt_active()) + static_branch_enable(&switch_to_cond_stibp); + else + static_branch_disable(&switch_to_cond_stibp); +} + void arch_smt_update(void) { /* Enhanced IBRS implies STIBP. No update required. */ @@ -567,6 +591,7 @@ void arch_smt_update(void) update_stibp_strict(); break; case SPECTRE_V2_USER_PRCTL: + update_indir_branch_cond(); break; } @@ -1038,7 +1063,8 @@ static char *stibp_state(void) case SPECTRE_V2_USER_STRICT: return ", STIBP: forced"; case SPECTRE_V2_USER_PRCTL: - return ""; + if (static_key_enabled(&switch_to_cond_stibp)) + return ", STIBP: conditional"; } return ""; } @@ -1046,14 +1072,11 @@ static char *stibp_state(void) static char *ibpb_state(void) { if (boot_cpu_has(X86_FEATURE_IBPB)) { - switch (spectre_v2_user) { - case SPECTRE_V2_USER_NONE: - return ", IBPB: disabled"; - case SPECTRE_V2_USER_STRICT: + if (static_key_enabled(&switch_mm_always_ibpb)) return ", IBPB: always-on"; - case SPECTRE_V2_USER_PRCTL: - return ""; - } + if (static_key_enabled(&switch_mm_cond_ibpb)) + return ", IBPB: conditional"; + return ", IBPB: disabled"; } return ""; }