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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 EC43DC43331 for ; Wed, 1 Apr 2020 22:30:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC7B92071A for ; Wed, 1 Apr 2020 22:30:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=citrix.com header.i=@citrix.com header.b="BghTe+Gj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732809AbgDAWaV (ORCPT ); Wed, 1 Apr 2020 18:30:21 -0400 Received: from esa4.hc3370-68.iphmx.com ([216.71.155.144]:17133 "EHLO esa4.hc3370-68.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732385AbgDAWaV (ORCPT ); Wed, 1 Apr 2020 18:30:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=citrix.com; s=securemail; t=1585780220; h=subject:to:cc:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=ypBqtZEADdvBfEkNyBIc74TZ0B3GOgvL58CLHWMq3dA=; b=BghTe+GjZGAnkwGOU/afP6eqbI7t2OVc8mMHXiN616OUqI5mOZepMLi2 mETUjLEfkFuphaUueaPUW4EzmFbNmPc+CO55K4Va6nH/ETf5YkkdSy/x5 b0jLvmQkqd7eAnLUvKZuJv4JafF5S6oxr4lWoh9dZkvA3IxeG/cDTM8ck M=; Authentication-Results: esa4.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none; spf=None smtp.pra=andrew.cooper3@citrix.com; spf=Pass smtp.mailfrom=Andrew.Cooper3@citrix.com; spf=None smtp.helo=postmaster@mail.citrix.com Received-SPF: None (esa4.hc3370-68.iphmx.com: no sender authenticity information available from domain of andrew.cooper3@citrix.com) identity=pra; client-ip=162.221.158.21; receiver=esa4.hc3370-68.iphmx.com; envelope-from="Andrew.Cooper3@citrix.com"; x-sender="andrew.cooper3@citrix.com"; x-conformance=sidf_compatible Received-SPF: Pass (esa4.hc3370-68.iphmx.com: domain of Andrew.Cooper3@citrix.com designates 162.221.158.21 as permitted sender) identity=mailfrom; client-ip=162.221.158.21; receiver=esa4.hc3370-68.iphmx.com; envelope-from="Andrew.Cooper3@citrix.com"; x-sender="Andrew.Cooper3@citrix.com"; x-conformance=sidf_compatible; x-record-type="v=spf1"; x-record-text="v=spf1 ip4:209.167.231.154 ip4:178.63.86.133 ip4:195.66.111.40/30 ip4:85.115.9.32/28 ip4:199.102.83.4 ip4:192.28.146.160 ip4:192.28.146.107 ip4:216.52.6.88 ip4:216.52.6.188 ip4:162.221.158.21 ip4:162.221.156.83 ip4:168.245.78.127 ~all" Received-SPF: None (esa4.hc3370-68.iphmx.com: no sender authenticity information available from domain of postmaster@mail.citrix.com) identity=helo; client-ip=162.221.158.21; receiver=esa4.hc3370-68.iphmx.com; envelope-from="Andrew.Cooper3@citrix.com"; x-sender="postmaster@mail.citrix.com"; x-conformance=sidf_compatible IronPort-SDR: SlBOpDVSyfmlaZYloDXfRtyji0AMLQW2ggHFzCnIad2qFJeMl2e6w5vnfnDP1epnj1a35l01GE gJ7p7IE9mrSXq7gTPDtz4HLJaxJsYAKLarA2Put92a64Iob8XDKqpo0/8TG+R+KdS4IwfCptHM 3sa/qfuCnMhgrFOog8P6Z8VQCurgolww554Z39ZPQ4r42ACZAW9vDKaDbgS46pyXIssmpFvjXA JMqF5IT32+YSitByXxOUC0NDPlCySni8S5lfM4ufZGVyGZGgHJW77gz+rXUO1e3O0guDB0wtz/ bH0= X-SBRS: 2.7 X-MesageID: 15694073 X-Ironport-Server: esa4.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.72,333,1580792400"; d="scan'208";a="15694073" Subject: Re: [PATCH] x86/smpboot: Remove 486-isms from the modern AP boot path To: "Maciej W. Rozycki" , Thomas Gleixner CC: , LKML , Ingo Molnar , Borislav Petkov , , "Jan Kiszka" , James Morris , "David Howells" , Matthew Garrett , Josh Boyer , Zhenzhong Duan , Steve Wahl , Mike Travis , Dimitri Sivanich , Arnd Bergmann , "Peter Zijlstra (Intel)" , Giovanni Gherdovich , "Rafael J. Wysocki" , Len Brown , Kees Cook , Martin Molnar , Pingfan Liu , References: <20200325101431.12341-1-andrew.cooper3@citrix.com> <601E644A-B046-4030-B3BD-280ABF15BF53@zytor.com> <87r1xgxzy6.fsf@nanos.tec.linutronix.de> From: Andrew Cooper Message-ID: Date: Wed, 1 Apr 2020 23:30:10 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Content-Language: en-GB X-ClientProxiedBy: AMSPEX02CAS01.citrite.net (10.69.22.112) To AMSPEX02CL02.citrite.net (10.69.22.126) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/04/2020 00:35, Maciej W. Rozycki wrote: > On Wed, 25 Mar 2020, Thomas Gleixner wrote: > >>>> @@ -1118,7 +1121,7 @@ static int do_boot_cpu(int apicid, int cpu, >>>> struct task_struct *idle, >>>> } >>>> } >>>> >>>> - if (x86_platform.legacy.warm_reset) { >>>> + if (!APIC_INTEGRATED(boot_cpu_apic_version)) { >>>> /* >>>> * Cleanup possible dangling ends... >>>> */ >>> We don't support SMP on 486 and haven't for a very long time. Is there >>> any reason to retain that code at all? >> Not that I'm aware off. > For the record: this code is for Pentium really, covering original P5 > systems, which lacked integrated APIC, as well as P54C systems that went > beyond dual (e.g. ALR made quad-SMP P54C systems). They all used external > i82489DX APICs for SMP support. Few were ever manufactured and getting > across one let alone running Linux might be tough these days. I never > managed to get one for myself, which would have been helpful for > maintaining this code. > > Even though we supported them by spec I believe we never actually ran MP > on any 486 SMP system (Alan Cox might be able to straighten me out on > this); none that I know of implemented the MPS even though actual hardware > might have used the APIC architecture. Compaq had its competing solution > for 486 and newer SMP, actually deployed, the name of which I long forgot. > We never supported it due to the lack of documentation combined with the > lack of enough incentive for someone to reverse-engineer it. :) I chose "486-ism" based on what the MP spec said about external vs integrated Local APICs.  I can't claim to have any experience of those days. I guess given v2 of the patch, I guess this should become "Remove external-LAPIC support from the AP boot path" ? ~Andrew