From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38687) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fC7tn-0002cC-5n for qemu-devel@nongnu.org; Fri, 27 Apr 2018 14:15:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fC7ti-0000cj-Ey for qemu-devel@nongnu.org; Fri, 27 Apr 2018 14:15:11 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:39308 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fC7ti-0000cN-8v for qemu-devel@nongnu.org; Fri, 27 Apr 2018 14:15:06 -0400 References: <20180427173416.19233-1-dgilbert@redhat.com> From: Eric Blake Message-ID: Date: Fri, 27 Apr 2018 13:14:53 -0500 MIME-Version: 1.0 In-Reply-To: <20180427173416.19233-1-dgilbert@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="OAgoze6oo59jTLtiEWVgxeo9CMbnjOxSn" Subject: Re: [Qemu-devel] [PATCH v2] migration: update docs List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert (git)" , qemu-devel@nongnu.org, bala24@linux.vnet.ibm.com, peterx@redhat.com, quintela@redhat.com This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --OAgoze6oo59jTLtiEWVgxeo9CMbnjOxSn From: Eric Blake To: "Dr. David Alan Gilbert (git)" , qemu-devel@nongnu.org, bala24@linux.vnet.ibm.com, peterx@redhat.com, quintela@redhat.com Message-ID: Subject: Re: [PATCH v2] migration: update docs References: <20180427173416.19233-1-dgilbert@redhat.com> In-Reply-To: <20180427173416.19233-1-dgilbert@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 04/27/2018 12:34 PM, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" >=20 > Update the migration docs: >=20 > Among other changes: > * Added a general list of advice for device authors > * Reordered the section on conditional state (subsections etc) > into the order we prefer. > * Add a note about firmware >=20 > Signed-off-by: Dr. David Alan Gilbert > --- > docs/devel/migration.rst | 531 +++++++++++++++++++++++++++------------= > 1 file changed, 375 insertions(+), 156 deletions(-) > + > +General advice for device developers > +------------------------------------ > + > +- The migration state saved should reflect the device being modelled r= ather > + than the way your implementation works. That way if you change the= implementation Three spaces between sentences is unusual. > + > +- The migration might happen at an inconvenient point, > + e.g. right in the middle of the guest reprogramming the device, duri= ng > + guest reboot or shutdown or while the device is waiting for external= IO. > + It's strongly preferred that migrations do not fail in this situatio= n, > + since in the cloud environment migrations might happen automatically= to > + VMs that the administrator doesn't directly control. Not for this patch, but is there any mechanism for a device to request that migration be delayed just long enough for the device to have a chance to get out of that inconsistent state, rather than having to migrate the inconvenient state? > +When we migrate a device, we save/load the state as a series > +of fields. Some times, due to bugs or new functionality, we need to Sometimes > @@ -328,9 +329,12 @@ Sometimes members of the VMState are no longer nee= ded: > =20 > - removing them will break migration compatibility > =20 > - - making them version dependent and bumping the version will break b= ackwards migration compatibility. > + - making them version dependent and bumping the version will break b= ackward migration compatibility. Is it worth worrying about long lines? --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org --OAgoze6oo59jTLtiEWVgxeo9CMbnjOxSn Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEzBAEBCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAlrjaJ0ACgkQp6FrSiUn Q2qHMQf/VJob3MzT1Gm7HgKrkLOv2TMSssu0sHgweIgmCZt0Z364eM6eYqI2T8Nj PvRlYJJ9c0P8XWVtrCU9K1n2dIrHKQwuFjNoaE102BM91j83c8bJYy7FREFJdcXN uhg3glMsjCPYsU/SLUZXNnHdD6z8yBxtpSBeAYE0LG5DBYr9skmT0Rit9c8oltu1 OzveMDga+l8r93flvVwD1QKOqiYWb3vDlksxbyCDIbe3r55yPPw8UjN8toWxyB+x a9uky2IyMyKNZVxkntWLhoHOYssxnShDudPiVbvJ/wIvBgzRsmBhyN4kYi5uPrFX QxgpoWN9luH9d2i+cEjfvIK2XTlPHQ== =dyWg -----END PGP SIGNATURE----- --OAgoze6oo59jTLtiEWVgxeo9CMbnjOxSn--