Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752083Ab3CAQai (ORCPT ); Fri, 1 Mar 2013 11:30:38 -0500 Received: from mx1.redhat.com ([209.132.183.28]:9083 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750778Ab3CAQag (ORCPT ); Fri, 1 Mar 2013 11:30:36 -0500 Message-ID: <5130D760.70908@redhat.com> Date: Fri, 01 Mar 2013 09:29:20 -0700 From: Eric Blake Organization: Red Hat, Inc. User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130219 Thunderbird/17.0.3 MIME-Version: 1.0 To: Hu Tao CC: kvm list , qemu-devel , "linux-kernel@vger.kernel.org" , "Daniel P. Berrange" , KAMEZAWA Hiroyuki , Jan Kiszka , Gleb Natapov , Blue Swirl , Andrew Jones , Marcelo Tosatti , Sasha Levin , Luiz Capitulino , Anthony Liguori , Markus Armbruster , Paolo Bonzini , Stefan Hajnoczi , Juan Quintela , Orit Wasserman , Kevin Wolf , Wen Congyang , "Michael S. Tsirkin" , Alexander Graf , Alex Williamson , Peter Maydell Subject: Re: [PATCH v13 1/8] save/load cpu runstate References: <512FC845.9080209@redhat.com> <20130301073648.GD16362@localhost.localdomain> In-Reply-To: <20130301073648.GD16362@localhost.localdomain> X-Enigmail-Version: 1.5.1 OpenPGP: url=http://people.redhat.com/eblake/eblake.gpg Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="----enig2IQQMSOUPJIDWITKASEXF" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3189 Lines: 75 This is an OpenPGP/MIME signed message (RFC 4880 and 3156) ------enig2IQQMSOUPJIDWITKASEXF Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 03/01/2013 12:36 AM, Hu Tao wrote: > On Thu, Feb 28, 2013 at 02:12:37PM -0700, Eric Blake wrote: >> On 02/28/2013 05:13 AM, Hu Tao wrote: >>> This patch enables preservation of cpu runstate during save/load vm. >>> So when a vm is restored from snapshot, the cpu runstate is restored,= >>> too. >> >> What happens if a management app wants to override the runstate when >> restoring the domain? I can think of several useful scenarios: >> >> 1. management app pauses the guest, then saves domain state and other >> things (management state, or disk clones), then resumes the guest. >> Later, the management wants to revert to the saved state, but have the= >> guest running right away. I guess here, knowing that the guest was >> saved in a paused state doesn't hurt, since the management app can >> resume it right away. >> >> 2. management app saves domain state of a live guest, then copies that= >> state elsewhere. In its new location, the management app wants to >> investigate the state for forensic analysis - so even though the guest= >> remembers that it was running, management wants to start it paused. >> Here, it is important that there must not be a window of time where th= e >> guest can run, otherwise, the results are not reproducible. >=20 > -S takes precedence in the case. But for in-migration, runstate is > loaded from src. Given your answer, I think we're okay from the libvirt perspective. My biggest worry about a window where the guest runs unchecked is not a problem, given that libvirt always uses -S on incoming migration. In turn, libvirt has its own mechanisms for tracking whether the outgoing migration was started from a running state, along with API overrides to let a user override whether libvirt will resume the guest on the incoming migration side. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org ------enig2IQQMSOUPJIDWITKASEXF Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.13 (GNU/Linux) Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJRMNdgAAoJEKeha0olJ0Nq0kEH/1SbK8p7fVUNjgKkqfpK8gb1 x/VQR88hsWDEeYO9wzaWjUIlS081QVm39kcGyeuYQFqtKA3ixUvIIuEDbtyzOS37 IQWQpwU0C/ILluJrQaqEFD77HwJAMi86SNVuQA2KvYOYXZrJIzKn5Q5ads1vDnPy pCv9nbwmu2kWc1rcXa9MPXqYq1yowsW5AWW0VM3m8tFIgc8VJbiSH/Ulku7KpzEu u0Xqun7tKOsF29l5TxMWwDPuSi/iPTovwpngz00VPQiMt5vrgj0rhA7Uj7xlWxyW DDT7Lf8OLlGbLEBsDAMDz0uwV5gZjl0ewaa5WIfGq+sYlfu0Lt1mzE+Ovq7R9r0= =F9rp -----END PGP SIGNATURE----- ------enig2IQQMSOUPJIDWITKASEXF-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/