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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 62CEBC04AB4 for ; Thu, 16 May 2019 15:59:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 404D32087E for ; Thu, 16 May 2019 15:59:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727402AbfEPP7I (ORCPT ); Thu, 16 May 2019 11:59:08 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:42610 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726813AbfEPP6o (ORCPT ); Thu, 16 May 2019 11:58:44 -0400 Received: from [167.98.27.226] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hRImH-0006zm-BS; Thu, 16 May 2019 16:58:41 +0100 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1hRImE-0001RV-Gd; Thu, 16 May 2019 16:58:38 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Thomas Gleixner" , "Jon Masters" , "Frederic Weisbecker" Date: Thu, 16 May 2019 16:55:33 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 64/86] x86/speculation/mds: Add BUG_MSBDS_ONLY In-Reply-To: X-SA-Exim-Connect-IP: 167.98.27.226 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.68-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner commit e261f209c3666e842fd645a1e31f001c3a26def9 upstream. This bug bit is set on CPUs which are only affected by Microarchitectural Store Buffer Data Sampling (MSBDS) and not by any other MDS variant. This is important because the Store Buffers are partitioned between Hyper-Threads so cross thread forwarding is not possible. But if a thread enters or exits a sleep state the store buffer is repartitioned which can expose data from one thread to the other. This transition can be mitigated. That means that for CPUs which are only affected by MSBDS SMT can be enabled, if the CPU is not affected by other SMT sensitive vulnerabilities, e.g. L1TF. The XEON PHI variants fall into that category. Also the Silvermont/Airmont ATOMs, but for them it's not really relevant as they do not support SMT, but mark them for completeness sake. Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Reviewed-by: Jon Masters Tested-by: Jon Masters [bwh: Backported to 3.16: - Assign the next available bug flag - Adjust context, indentation] Signed-off-by: Ben Hutchings --- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/kernel/cpu/common.c | 20 ++++++++++++-------- 2 files changed, 13 insertions(+), 8 deletions(-) --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -273,5 +273,6 @@ #define X86_BUG_SPEC_STORE_BYPASS X86_BUG(8) /* CPU is affected by speculative store bypass attack */ #define X86_BUG_L1TF X86_BUG(9) /* CPU is affected by L1 Terminal Fault */ #define X86_BUG_MDS X86_BUG(10) /* CPU is affected by Microarchitectural data sampling */ +#define X86_BUG_MSBDS_ONLY X86_BUG(11) /* CPU is only affected by the MSDBS variant of BUG_MDS */ #endif /* _ASM_X86_CPUFEATURES_H */ --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -812,6 +812,7 @@ static void identify_cpu_without_cpuid(s #define NO_SSB BIT(2) #define NO_L1TF BIT(3) #define NO_MDS BIT(4) +#define MSBDS_ONLY BIT(5) #define VULNWL(_vendor, _family, _model, _whitelist) \ { X86_VENDOR_##_vendor, _family, _model, X86_FEATURE_ANY, _whitelist } @@ -835,16 +836,16 @@ static const __initconst struct x86_cpu_ VULNWL_INTEL(ATOM_BONNELL, NO_SPECULATION), VULNWL_INTEL(ATOM_BONNELL_MID, NO_SPECULATION), - VULNWL_INTEL(ATOM_SILVERMONT, NO_SSB | NO_L1TF), - VULNWL_INTEL(ATOM_SILVERMONT_X, NO_SSB | NO_L1TF), - VULNWL_INTEL(ATOM_SILVERMONT_MID, NO_SSB | NO_L1TF), - VULNWL_INTEL(ATOM_AIRMONT, NO_SSB | NO_L1TF), - VULNWL_INTEL(XEON_PHI_KNL, NO_SSB | NO_L1TF), - VULNWL_INTEL(XEON_PHI_KNM, NO_SSB | NO_L1TF), + VULNWL_INTEL(ATOM_SILVERMONT, NO_SSB | NO_L1TF | MSBDS_ONLY), + VULNWL_INTEL(ATOM_SILVERMONT_X, NO_SSB | NO_L1TF | MSBDS_ONLY), + VULNWL_INTEL(ATOM_SILVERMONT_MID, NO_SSB | NO_L1TF | MSBDS_ONLY), + VULNWL_INTEL(ATOM_AIRMONT, NO_SSB | NO_L1TF | MSBDS_ONLY), + VULNWL_INTEL(XEON_PHI_KNL, NO_SSB | NO_L1TF | MSBDS_ONLY), + VULNWL_INTEL(XEON_PHI_KNM, NO_SSB | NO_L1TF | MSBDS_ONLY), VULNWL_INTEL(CORE_YONAH, NO_SSB), - VULNWL_INTEL(ATOM_AIRMONT_MID, NO_L1TF), + VULNWL_INTEL(ATOM_AIRMONT_MID, NO_L1TF | MSBDS_ONLY), VULNWL_INTEL(ATOM_GOLDMONT, NO_MDS | NO_L1TF), VULNWL_INTEL(ATOM_GOLDMONT_X, NO_MDS | NO_L1TF), @@ -888,8 +889,11 @@ static void __init cpu_set_bug_bits(stru if (ia32_cap & ARCH_CAP_IBRS_ALL) setup_force_cpu_cap(X86_FEATURE_IBRS_ENHANCED); - if (!cpu_matches(NO_MDS) && !(ia32_cap & ARCH_CAP_MDS_NO)) + if (!cpu_matches(NO_MDS) && !(ia32_cap & ARCH_CAP_MDS_NO)) { setup_force_cpu_bug(X86_BUG_MDS); + if (cpu_matches(MSBDS_ONLY)) + setup_force_cpu_bug(X86_BUG_MSBDS_ONLY); + } if (cpu_matches(NO_MELTDOWN)) return;