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=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT 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 89F18C4321D for ; Fri, 24 Aug 2018 12:21:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 288162098B for ; Fri, 24 Aug 2018 12:21:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 288162098B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 S1726570AbeHXPzY (ORCPT ); Fri, 24 Aug 2018 11:55:24 -0400 Received: from mx2.suse.de ([195.135.220.15]:41676 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726471AbeHXPzY (ORCPT ); Fri, 24 Aug 2018 11:55:24 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B086CB070; Fri, 24 Aug 2018 12:20:56 +0000 (UTC) Date: Fri, 24 Aug 2018 14:20:56 +0200 From: Michal Hocko To: Vlastimil Babka Cc: Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds , Andi Kleen , Dave Hansen , stable@vger.kernel.org Subject: Re: [PATCH] x86/speculation/l1tf: suggest what to do on systems with too much RAM Message-ID: <20180824122056.GM29735@dhcp22.suse.cz> References: <20180823134418.17008-1-vbabka@suse.cz> <20180823142812.7363-1-vbabka@suse.cz> <20180823192709.GT29735@dhcp22.suse.cz> <966571f0-9d7f-43dc-92c6-a10eec7a1254@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 24-08-18 14:10:54, Vlastimil Babka wrote: > On 08/24/2018 12:36 PM, Vlastimil Babka wrote: > > On 08/24/2018 09:32 AM, Vlastimil Babka wrote: > >> On 08/23/2018 09:27 PM, Michal Hocko wrote: > >>> On Thu 23-08-18 16:28:12, Vlastimil Babka wrote: > >>>> 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. Let's > >>>> make the warning more helpful by suggesting the proper mem=X kernel boot param, > >>>> a rough calculation of how much RAM can be lost (not precise if there's holes > >>>> between MAX_PA/2 and max_pfn in the e820 map) 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 > >>>> Cc: stable@vger.kernel.org > >>>> Signed-off-by: Vlastimil Babka > >>> > >>> I wouldn't bother with max_pfn-half_pa part but other than that this is > >>> much more useful than the original message. > >> > >> Right, and it causes build failures on some configs. > >> > >>> Acked-by: Michal Hocko > >> > >> Thanks! Here's a v2: > > > > Just realized that kvm printk's refer to the online version at > > https://www.kernel.org/doc/html/latest/admin-guide/l1tf.html > > which should be easier for the users of distro kernels, should I change > > that? > > FWIW, if it's not possible to amend anymore... > ----8<---- > >From a650e6a4b989c6e029ac1ab4e0a68553e074ba7a Mon Sep 17 00:00:00 2001 > From: Vlastimil Babka > Date: Fri, 24 Aug 2018 14:05:45 +0200 > Subject: [PATCH] x86/speculation/l1tf: replace Documentation path with > kernel.org URL > > The URL might be easier to reach for users of distro kernels without unpacked > source, and be more up-to-date. It's also used in KVM warnings related to L1TF. Yes, URL is much more convenient than a reference to the kernel source documentation. If the link below is meant to be long lived then sure. > Signed-off-by: Vlastimil Babka Acked-by: Michal Hocko > --- > arch/x86/kernel/cpu/bugs.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c > index 5c32b5006738..4c2313d0b9ca 100644 > --- a/arch/x86/kernel/cpu/bugs.c > +++ b/arch/x86/kernel/cpu/bugs.c > @@ -705,7 +705,7 @@ static void __init l1tf_select_mitigation(void) > 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"); > + pr_info("Reading https://www.kernel.org/doc/html/latest/admin-guide/l1tf.html might help you decide.\n"); > return; > } > > -- > 2.18.0 > > > -- Michal Hocko SUSE Labs