From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?B?TWFyY2luIEdpYnXFgmE=?= Subject: Re: [Qemu-devel] [PATCH] kvmclock: Ensure time in migration never goes backward Date: Mon, 05 May 2014 20:26:04 +0200 Message-ID: <5367D7BC.2040705@beyond.pl> References: <1399297882-3444-1-git-send-email-agraf@suse.de> <5367CE81.6030506@beyond.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: "qemu-devel@nongnu.org" , "kvm@vger.kernel.org" To: Alexander Graf Return-path: Received: from mx.beyond.pl ([92.43.117.49]:40188 "EHLO mx.beyond.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751599AbaEES0M (ORCPT ); Mon, 5 May 2014 14:26:12 -0400 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: >> is it possible to have kvmclock jumping forward? >> >> Because I've reproducible case when at about 1 per 20 vm restores, VM freezes for couple of hours and then resumes with date few hundreds years ahead. Happens only with kvmclock. >> >> And this patch seems to fix very similar issue so maybe it's all the same bug. > > I'm fairly sure it is the exact same bug. Jumping backward is like jumping forward by a biiiiig amount :) Hi, I've tested your path on my test VM... don't know if it's pure luck or not, but it didn't hang with over 70 restores. The message "KVM Clock migrated backwards, using later time" fires every time, but VM is healthy after resume. -- mg