From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44463) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XC6zc-0004xn-6Y for qemu-devel@nongnu.org; Tue, 29 Jul 2014 08:59:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XC6zX-0006qj-8K for qemu-devel@nongnu.org; Tue, 29 Jul 2014 08:59:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:5034) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XC6zX-0006qf-0l for qemu-devel@nongnu.org; Tue, 29 Jul 2014 08:58:55 -0400 Message-ID: <53D79A8A.9060500@redhat.com> Date: Tue, 29 Jul 2014 06:58:50 -0600 From: Eric Blake MIME-Version: 1.0 References: <1406219965-13214-1-git-send-email-stefanha@redhat.com> <1406219965-13214-3-git-send-email-stefanha@redhat.com> <87ppgtvovi.fsf@blackfin.pond.sub.org> <53D6D7EC.7090602@redhat.com> <8761igy9qn.fsf@blackfin.pond.sub.org> In-Reply-To: <8761igy9qn.fsf@blackfin.pond.sub.org> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="kX8T9D1TB4avTPl8nttbRiE0SUwDRCbvN" Subject: Re: [Qemu-devel] [PATCH 2/3] qemu-char: add -chardev exit-on-eof option List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: Andreas Faerber , qemu-devel@nongnu.org, Stefan Hajnoczi , Anthony Liguori This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --kX8T9D1TB4avTPl8nttbRiE0SUwDRCbvN Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 07/29/2014 12:12 AM, Markus Armbruster wrote: >> Libvirt probably won't use it for normal guests (we don't want to kill= >> qemu just because the monitor disconnects), but does have the notion o= f >> an autodestroy guest where it might be useful (we WANT the guest to go= >> away if libvirtd dies early). In fact, autodestroy guests are used >> during migration - we want to kill qemu on the destination side if >> libvirtd dies before the source side finishes sending the migration >> stream. But in that scenario, once migration succeeds, libvirt has to= >> be able to convert an autodestroy guest back into a normal guest that = no >> longer disappears when libvirtd does; would this be something that QMP= >> can toggle the state of this attribute on the fly? Perhaps through qo= m-set? >=20 > After migration completes, execution moves from source to target. > Wouldn't you want to switch off target auto-destruct together with that= > move, atomically? Libvirt starts the destination with -S, and migration can't complete until libvirt resumes the destination CPUs with 'cont'. Libvirt's current timing of releasing auto-destruct is based on handshaking between source and destination; it occurs after source claims migration is done but before resuming CPUs on the destination, which satisfies the atomicity that you correctly observed to be necessary. >> However, we also have precedence of actions in QAPI that are very >> unlikely to be used outside of qtest, but which are not marked >> experimental; for example, the 'Abort' action in 'transaction' will >> probably never be used by libvirt >=20 > Arguably not a conscious decision to make it ABI forever, more a case o= f > nobody thought about *not* making it ABI :) Added in June 2013; and we *did* have a discussion on whether to hide the transaction name at the time... https://lists.gnu.org/archive/html/qemu-devel/2013-06/msg03281.html > I don't really mind this instance, but I'm a bit concerned about rank > ABI growth. And that's a good position to maintain - it's always good to justify new knobs, especially since once they are ABI, it's harder to refactor around them. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --kX8T9D1TB4avTPl8nttbRiE0SUwDRCbvN 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 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg iQEcBAEBCAAGBQJT15qKAAoJEKeha0olJ0NqJMEH/jky5gtbFl9Nrrrsyq4AftRD nBPk8qJMkZyOt6UIjkuZKZ9OWgkfhUW8YPL9LVcR+CuguWXb6/8PJk19vN1bl0nE ku2ysQ9LgvSTAZWwb+PT1HHyvkL5QP0xwvlszJg9MRsUE8bhLW/ZyT8fTFKkSdI6 3nXpfqAjPBcovFTYQq+QL+BlX7PiDjBIuXzAdysiHu5qC1RXpBqrDGF5K+vUogcW Bf8WFPoPk09x1QJS7etbMMu21dPlXiRDWU0GBSmgz/GWiOOdHhk+bO7thm4GU2GA qI/buQg0Vm4ksW2oa8fGdFbv6z8bPBRf3FE1QEuZFOCA3rMQS2CvG2hG2sDc4Bg= =GeCH -----END PGP SIGNATURE----- --kX8T9D1TB4avTPl8nttbRiE0SUwDRCbvN--