From patchwork Tue Feb 9 12:53:48 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Beulich X-Patchwork-Id: 12078039 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=-7.3 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 37C46C433DB for ; Tue, 9 Feb 2021 12:54:06 +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 AC97964D9D for ; Tue, 9 Feb 2021 12:54:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AC97964D9D 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.83219.154293 (Exim 4.92) (envelope-from ) id 1l9SWd-0007YF-Cm; Tue, 09 Feb 2021 12:53:51 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 83219.154293; Tue, 09 Feb 2021 12:53:51 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l9SWd-0007Y8-9f; Tue, 09 Feb 2021 12:53:51 +0000 Received: by outflank-mailman (input) for mailman id 83219; Tue, 09 Feb 2021 12:53:50 +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 1l9SWc-0007Y3-IE for xen-devel@lists.xenproject.org; Tue, 09 Feb 2021 12:53:50 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 7051a01d-c083-4310-826b-3ebb13ffd65e; Tue, 09 Feb 2021 12:53:49 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 16D30AD6A; Tue, 9 Feb 2021 12:53:48 +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: 7051a01d-c083-4310-826b-3ebb13ffd65e 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=1612875228; 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=Xz6SEvYbpCIel5pRUo0p4mEoQEJzeymHCtV40pnxtHo=; b=mPpH3gVnMlhRoqlew3FuZ+8Yc0SppIiRiIjukJWGMOVwWLn9+HNk38eF8di/GOj7gJd3UH brVdcAqtG9HfRJFU/YEJor53qrOumR6RvhR7qG+Bs16Uj2jHC69KdERG34FJUgwdn54PIQ qVX74kblIKXqB8/Ts2SP+WI3YbTdRJg= From: Jan Beulich Subject: [PATCH v3 0/4] 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 , Ian Jackson Message-ID: Date: Tue, 9 Feb 2021 13:53:48 +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 Content-Language: en-US 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. 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() 4: re-arrange struct calibration_rendezvous Jan