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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 72C68ECDFB8 for ; Mon, 23 Jul 2018 09:29:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3510B20854 for ; Mon, 23 Jul 2018 09:29:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3510B20854 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lxorguk.ukuu.org.uk 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 S2388191AbeGWKaD (ORCPT ); Mon, 23 Jul 2018 06:30:03 -0400 Received: from www.llwyncelyn.cymru ([82.70.14.225]:45150 "EHLO fuzix.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388080AbeGWKaC (ORCPT ); Mon, 23 Jul 2018 06:30:02 -0400 Received: from alans-desktop (82-70-14-226.dsl.in-addr.zen.co.uk [82.70.14.226]) by fuzix.org (8.15.2/8.15.2) with ESMTP id w6N9Sfve029815; Mon, 23 Jul 2018 10:28:41 +0100 Date: Mon, 23 Jul 2018 10:28:41 +0100 From: Alan Cox To: Pavel Tatashin Cc: Thomas Gleixner , peterz@infradead.org, Steven Sistare , Daniel Jordan , linux@armlinux.org.uk, schwidefsky@de.ibm.com, Heiko Carstens , John Stultz , sboyd@codeaurora.org, x86@kernel.org, LKML , mingo@redhat.com, hpa@zytor.com, douly.fnst@cn.fujitsu.com, prarit@redhat.com, feng.tang@intel.com, Petr Mladek , linux-s390@vger.kernel.org, boris.ostrovsky@oracle.com, jgross@suse.com, pbonzini@redhat.com Subject: Re: [PATCH v14 20/25] x86/tsc: calibrate tsc only once Message-ID: <20180723102841.58ea373b@alans-desktop> In-Reply-To: References: <20180718022211.6259-1-pasha.tatashin@oracle.com> <20180718022211.6259-21-pasha.tatashin@oracle.com> <20180719103340.GA2494@hirez.programming.kicks-ass.net> <4295075b-8a0f-1723-2e80-1bbd2f038846@oracle.com> Organization: Intel Corporation X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > >> If we determined tsc early in boot using one of the quick methods: > >> from cpuid/msr/quick_pit, can we assume that frequencies of all other > >> CPUs will be determined the same way? Or do we still have to fallback Not on 32bit at least. You can have a mixed slot 1 SMP system such as an ASUS BP6 with cores at say 300 and 450MHz. Now whether you'll find any such system in the world today is another question. Alan