From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753747Ab1LGHpG (ORCPT ); Wed, 7 Dec 2011 02:45:06 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59117 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753219Ab1LGHpE (ORCPT ); Wed, 7 Dec 2011 02:45:04 -0500 Date: Wed, 7 Dec 2011 13:14:56 +0530 From: Amit Shah To: Rusty Russell Cc: Virtualization List , "Michael S. Tsirkin" , levinsasha928@gmail.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 00/12] virtio: s4 support Message-ID: <20111207074456.GD4651@amit-x200.redhat.com> References: <87wra8j13m.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87wra8j13m.fsf@rustcorp.com.au> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (Wed) 07 Dec 2011 [17:54:29], Rusty Russell wrote: > On Wed, 7 Dec 2011 01:18:38 +0530, Amit Shah wrote: > > Hi, > > > > These patches add support for S4 to virtio (pci) and all drivers. > > Dumb meta-question: why do we want to hibernate virtual machines? Not a dumb question at all :) But that doesn't mean I can't give a dumb answer: "Because We Can". > I figure there's a reason, but it seems a bit weird :) Well, there is one reason right now: migrating storage along with VMs. The guest needs to sync all data to the disk before the target host accesses the image file. One way to make sure guests don't access the disk is by adding a new guest command to stop disk accesses. However, we already have one way of making guests stop doing whatever they are by putting them into S4 state, and then waking them up on the remote, with them thinking nothing about them has changed. (Did I manage to make this sound desirable after the answer above? :) Amit