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[209.132.180.67]) by mx.google.com with ESMTP id e1-v6si6494759pli.469.2018.08.24.00.57.55; Fri, 24 Aug 2018 00:58:10 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727991AbeHXLaM (ORCPT + 99 others); Fri, 24 Aug 2018 07:30:12 -0400 Received: from terminus.zytor.com ([198.137.202.136]:56965 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727955AbeHXLaL (ORCPT ); Fri, 24 Aug 2018 07:30:11 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id w7O7tX5h3564735 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Fri, 24 Aug 2018 00:55:33 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id w7O7tWex3564727; Fri, 24 Aug 2018 00:55:32 -0700 Date: Fri, 24 Aug 2018 00:55:32 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Vlastimil Babka Message-ID: Cc: tglx@linutronix.de, dave.hansen@intel.com, mingo@kernel.org, ak@linux.intel.com, hpa@zytor.com, linux-kernel@vger.kernel.org, mhocko@suse.com, vbabka@suse.cz, torvalds@linux-foundation.org Reply-To: linux-kernel@vger.kernel.org, mhocko@suse.com, torvalds@linux-foundation.org, vbabka@suse.cz, hpa@zytor.com, ak@linux.intel.com, mingo@kernel.org, dave.hansen@intel.com, tglx@linutronix.de In-Reply-To: <966571f0-9d7f-43dc-92c6-a10eec7a1254@suse.cz> References: <966571f0-9d7f-43dc-92c6-a10eec7a1254@suse.cz> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/speculation/l1tf: Suggest what to do on systems with too much RAM Git-Commit-ID: 4b81eae3d37dee69231592182e1e34706f149a6e 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 X-Spam-Status: No, score=-2.9 required=5.0 tests=ALL_TRUSTED,BAYES_00, T_DATE_IN_FUTURE_96_Q autolearn=ham autolearn_force=no version=3.4.1 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on terminus.zytor.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 4b81eae3d37dee69231592182e1e34706f149a6e Gitweb: https://git.kernel.org/tip/4b81eae3d37dee69231592182e1e34706f149a6e Author: Vlastimil Babka AuthorDate: Thu, 23 Aug 2018 16:21:29 +0200 Committer: Thomas Gleixner CommitDate: Fri, 24 Aug 2018 09:51:14 +0200 x86/speculation/l1tf: Suggest what to do on systems with too much RAM Two users have reported [1] that they have an "extremely unlikely" system with more than MAX_PA/2 memory and L1TF mitigation is not effective. Make the warning more helpful by suggesting the proper mem=X kernel boot parameter to make it effective and a link to the L1TF document to help decide if the mitigation is worth the unusable RAM. [1] https://bugzilla.suse.com/show_bug.cgi?id=1105536 Suggested-by: Michal Hocko Signed-off-by: Vlastimil Babka Acked-by: Michal Hocko Cc: "H . Peter Anvin" Cc: Linus Torvalds Cc: Andi Kleen Cc: Dave Hansen Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/966571f0-9d7f-43dc-92c6-a10eec7a1254@suse.cz --- arch/x86/kernel/cpu/bugs.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index cb4a16292aa7..5c32b5006738 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -702,6 +702,10 @@ static void __init l1tf_select_mitigation(void) half_pa = (u64)l1tf_pfn_limit() << PAGE_SHIFT; if (e820__mapped_any(half_pa, ULLONG_MAX - half_pa, E820_TYPE_RAM)) { pr_warn("System has more than MAX_PA/2 memory. L1TF mitigation not effective.\n"); + pr_info("You may make it effective by booting the kernel with mem=%llu parameter.\n", + half_pa); + pr_info("However, doing so will make a part of your RAM unusable.\n"); + pr_info("Reading Documentation/admin-guide/l1tf.rst might help you decide.\n"); return; }