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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 06699C43387 for ; Mon, 7 Jan 2019 23:48:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CE27E2183E for ; Mon, 7 Jan 2019 23:48:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727342AbfAGXs5 (ORCPT ); Mon, 7 Jan 2019 18:48:57 -0500 Received: from nautica.notk.org ([91.121.71.147]:35419 "EHLO nautica.notk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726667AbfAGXs5 (ORCPT ); Mon, 7 Jan 2019 18:48:57 -0500 Received: by nautica.notk.org (Postfix, from userid 1001) id 258CFC01B; Tue, 8 Jan 2019 00:48:54 +0100 (CET) Date: Tue, 8 Jan 2019 00:48:39 +0100 From: Dominique Martinet To: Pavel Tatashin Cc: Salvatore Bonaccorso , Steven Sistare , Pavel Tatashin , Daniel Jordan , linux@armlinux.org.uk, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, John Stultz , sboyd@codeaurora.org, x86@kernel.org, LKML , mingo@redhat.com, Thomas Gleixner , hpa@zytor.com, douly.fnst@cn.fujitsu.com, Peter Zijlstra , prarit@redhat.com, feng.tang@intel.com, Petr Mladek , gnomes@lxorguk.ukuu.org.uk, linux-s390@vger.kernel.org, boris.ostrovsky@oracle.com, jgross@suse.com, pbonzini@redhat.com, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, qemu-devel@nongnu.org Subject: Re: [PATCH v15 23/26] sched: early boot clock Message-ID: <20190107234839.GA15269@nautica> References: <20180719205545.16512-1-pasha.tatashin@oracle.com> <20180719205545.16512-24-pasha.tatashin@oracle.com> <20181106054212.GA31768@nautica> <95c3920e-bf80-0c7e-7854-01a1c3189c23@oracle.com> <20190102202032.GA1034@eldamar.local> <20190103234339.GA17457@nautica> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Pavel Tatashin wrote on Mon, Jan 07, 2019: > I could not reproduce the problem. Did you suspend to memory between > wake ups? Does this time jump happen every time, even if your laptop > sleeps for a minute? I'm not sure I understand "suspend to memory between the wake ups". The full sequence is: - start a VM (just in case, I let it boot till the end) - suspend to memory (aka systemctl suspend) the host - after resuming the host, soft reboot the VM (login through serial/ssh/whatever and reboot or in the qemu console 'system_reset') I've just slept exactly one minute and reproduced again with the fedora stock kernel now (4.19.13-300.fc29.x86_64) in the VM. Interestingly I'm not getting the same offset between multiple reboots now despite not suspending again; but if I don't suspend I cannot seem to get it to give an offset at all (only tried for a few minutes; this might not be true) ; OTOH I pushed my luck further and even with a five seconds sleep I'm getting a noticeable offset on first VM reboot after resume: [ 0.000000] Hypervisor detected: KVM [ 0.000000] kvm-clock: Using msrs 4b564d01 and 4b564d00 [ 179.362163] kvm-clock: cpu 0, msr 13c01001, primary cpu clock [ 179.362163] clocksource: kvm-clock: mask: 0xffffffffffffffff max_cycles: 0x1cd42e4dffb, max_idle_ns: 881590591483 ns Honestly not sure what more information I could give, I'll try on some other hardware than my laptop (if I can get a server to resume after suspend through ipmi or wake on lan); but I don't have anything I could install ubuntu on to try their qemu's version... although I really don't want to believe that's the difference... Thanks, -- Dominique