From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: TSC deadline timer in guests vs. migration?
Date: Mon, 4 Jul 2016 16:30:08 -0300
Message-ID: <20160704193005.GA28201@amt.cnet>
References: <759376f0-e0bf-e53a-99e4-598bf14547e3@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Eduardo Habkost <ehabkost@redhat.com>,
	David Matlack <dmatlack@google.com>,
	Peter Hornyack <peterhornyack@google.com>,
	KVM list <kvm@vger.kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mx1.redhat.com ([209.132.183.28]:40694 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1753362AbcGDTan (ORCPT <rfc822;kvm@vger.kernel.org>);
	Mon, 4 Jul 2016 15:30:43 -0400
Content-Disposition: inline
In-Reply-To: <759376f0-e0bf-e53a-99e4-598bf14547e3@redhat.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

On Mon, Jul 04, 2016 at 01:01:42PM +0200, Paolo Bonzini wrote:
> Can bad things happen if a guest using the TSC deadline timer is
> migrated?  The guest doesn't re-calibrate the TSC after migration, and
> the TSC frequency can and will change unless your data center is
> perfectly homogeneous.

It can fire earlier if the destination runs at a higher frequency.
It will fire past the configured time if the destination runs at a slower frequency.

Suppose the first case is worse.

Should convert the expiration time to nanoseconds i suppose, and then 
convert back on the destination.