From patchwork Mon Feb 1 12:41:41 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Beulich X-Patchwork-Id: 12058947 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=-7.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 76C1EC433E0 for ; Mon, 1 Feb 2021 12:42:03 +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 3265964DAF for ; Mon, 1 Feb 2021 12:42:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3265964DAF 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.79836.145447 (Exim 4.92) (envelope-from ) id 1l6YWZ-0003Ay-VP; Mon, 01 Feb 2021 12:41:47 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 79836.145447; Mon, 01 Feb 2021 12:41:47 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l6YWZ-0003Ar-SA; Mon, 01 Feb 2021 12:41:47 +0000 Received: by outflank-mailman (input) for mailman id 79836; Mon, 01 Feb 2021 12:41:46 +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 1l6YWX-0003Am-UU for xen-devel@lists.xenproject.org; Mon, 01 Feb 2021 12:41:45 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 864af19d-4885-4521-bd63-36209379be20; Mon, 01 Feb 2021 12:41:43 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id D2A4DAB92; Mon, 1 Feb 2021 12:41:42 +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: 864af19d-4885-4521-bd63-36209379be20 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=1612183302; 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; bh=eNLWhHPDsMuX+VaPLPf7HucG8rgFqcAlJfgfgBVrV1o=; b=hz08KS8bNOMxQvHLXzdLz303Ow4YoL3Pp1OU9PAdCoCEFa4HelH8jXVjP4oUQgTJteD0ab +xOxO7LcUGSvpQd4QArHku3+7v/gU66nooYuQux1FaMan7W5wPsgNRoqlpJBVhRt1eL5TB c/AMGgD9Or0OkQAjbleXX9+Nw6I5VNI= From: Jan Beulich Subject: [PATCH v2 0/3] x86/time: calibration rendezvous adjustments To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , Wei Liu , =?utf-8?q?Roger_Pau_Monn=C3=A9?= , Claudemir Todo Bom Message-ID: Date: Mon, 1 Feb 2021 13:41:41 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 Content-Language: en-US The latter 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. While looking closely at the corresponding debugging patch'es output I noticed a suspicious drift between local and master stime: Measured not very precisely, local was behind master by about 200ms in about half an hour. Interestingly the recording of ->master_stime (and hence the not really inexpensive invocation of read_platform_stime()) looks to be pretty pointless when CONSTANT_TSC - I haven't been able to spot an actual consumer. IOW the drift may not be a problem, and we might be able to eliminate the platform timer reads. (When !CONSTANT_TSC, such drift would get corrected anyway, by local_time_calibration().) 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() Jan