From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33145) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZQAiP-0000ab-PY for qemu-devel@nongnu.org; Fri, 14 Aug 2015 04:51:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZQAiL-00035Y-Or for qemu-devel@nongnu.org; Fri, 14 Aug 2015 04:51:53 -0400 Received: from ip-92-43-119-196.beyond.pl ([92.43.119.196]:38695 helo=mx.beyond.pl) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZQAiL-00035Q-HE for qemu-devel@nongnu.org; Fri, 14 Aug 2015 04:51:49 -0400 References: <20150813221650.GA8109@amt.cnet> <55CD9968.7000202@beyond.pl> From: =?UTF-8?Q?Marcin_Gibu=c5=82a?= Message-ID: <55CDAC18.4060406@beyond.pl> Date: Fri, 14 Aug 2015 10:51:36 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=iso-8859-2; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] about the patch kvmclock Ensure proper env->tsc value for kvmclock_current_nsec calculation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: liang.z.li@intel.com > Thanks for your reply, I have read the thread in your email, what's the mean of 'switching from old to new disk', could give a detail description? The test case was like that (using libvirt): 1. Get VM running (linux, using kvmclock), 2. Use blockcopy to copy disk data from one location to another, 3. Issue blockjob --pivot (to finish mirroring) From what I remember, at point 3, VM is momentarily paused and resumed, so kvm state change handler is called twice. Without this patch, the VM hanged because its time goes backwards (or qemu crashed if assertion was not compiled out). -- mg