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=-7.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,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 5FC55C433E6 for ; Tue, 9 Feb 2021 13:02:35 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0B44964E2E for ; Tue, 9 Feb 2021 13:02:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0B44964E2E Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.83234.154368 (Exim 4.92) (envelope-from ) id 1l9Seq-0000ka-Mo; Tue, 09 Feb 2021 13:02:20 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 83234.154368; Tue, 09 Feb 2021 13:02:20 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l9Seq-0000kT-IT; Tue, 09 Feb 2021 13:02:20 +0000 Received: by outflank-mailman (input) for mailman id 83234; Tue, 09 Feb 2021 13:02:19 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l9Seo-0000kL-Vd for xen-devel@lists.xenproject.org; Tue, 09 Feb 2021 13:02:19 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id fdd56266-18b9-45e0-8ced-70d5c545f552; Tue, 09 Feb 2021 13:02:17 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id BD7CAAD6A; Tue, 9 Feb 2021 13:02:16 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: fdd56266-18b9-45e0-8ced-70d5c545f552 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1612875736; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pm1SXLBpvnL4ukE2e2l7lHTnGHmAvihoOGdi1YBFjwM=; b=VUxofy4sEx8Fhj1IzhsRGNvv+K+xEMVx4cMyo+VqbgiGnoZhbG/5NNlJYnNoQsTEEPPyjl kr7UnwQe4gGSqGUd0np5KeBnBtzlkEDnwj6df6shvJBOsrCV/KfpUctezTG8uiEJR7ZtUD bL7MJexcf8N1Zv7w4CyWaDdAZV2gS28= Subject: Re: [PATCH v3 0/4] x86/time: calibration rendezvous adjustments From: Jan Beulich To: Ian Jackson Cc: Andrew Cooper , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , "xen-devel@lists.xenproject.org" References: Message-ID: Date: Tue, 9 Feb 2021 14:02:17 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 09.02.2021 13:53, Jan Beulich wrote: > The middle two patches are meant to address a regression reported on > the list under "Problems with APIC on versions 4.9 and later (4.8 > works)". In the course of analyzing output from a debugging patch I > ran into another anomaly again, which I thought I should finally try > to address. Hence patch 1. Patch 4 is new in v3 and RFC for now. Of course this is the kind of change I'd prefer doing early in a release cycle. I don't think there are severe risks from patch 1, but I'm not going to claim patches 2 and 3 are risk free. They fix booting Xen on a system left in rather awkward state by the firmware. And they shouldn't affect well behaved modern systems at all (due to those using a different rendezvous function). While we've been having this issue for years, I also consider this set a backporting candidate. Hence I can see reasons pro and con inclusion in 4.15. Jan > 1: change initiation of the calibration timer > 2: adjust time recording time_calibration_tsc_rendezvous() > 3: don't move TSC backwards in time_calibration_tsc_rendezvous() > 4: re-arrange struct calibration_rendezvous > > Jan >