-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Il 15/07/2013 23:33, Eric Blake ha scritto: >>>>> Newer libvirt can be taught to append 'M' when it detects >>>>> it is talking to newer qemu. While you have a point that >>>>> it is annoying to force users to upgrade to a newer libvirt >>>>> merely because they upgraded qemu, the libvirt point of >>>>> view is that the following are supported: >>>>> >>>>> old libvirt -> old qemu new libvirt -> old qemu new libvirt >>>>> -> new qemu >>>>> >>>>> but that this combination is always best effort and not >>>>> required to work: >>>>> >>>>> old libvirt -> new qemu >>> >>> I don't think this is the case, unless you're talking of *very* >>> old libvirt (e.g. pre-QMP). > As a counter-example, I can recall a case where a qemu release that > used just two digits (was that 1.2?) broke operation under older > libvirt that assumed versions would always be three digits; but it > definitely occurred after 0.15.x which is the point at which > libvirt started favoring QMP. That is, we had a case in Fedora > where if you upgraded qemu, you HAD to also update libvirt to be > able to keep your guests running.
Right, I remember that now. So, better: "we have some interfaces which are considered API, and old libvirt -> new QEMU should not break for things that use those interfaces". QMP and the command line are definitely one. The case you mentioned was about -help, if I remember correctly, which was indeed quite brittle (like HMP). > But yes, the goal of having command line compatibility, so that > any application using the same command line it always uses will get > the same guest, regardless of a qemu upgrade in the meantime, > should be our default mode of operation, even if newer apps should > prefer newer (better) command line interfaces. Yes, the command line *is* part of the API. Paolo -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQIcBAEBAgAGBQJR5OcaAAoJEBvWZb6bTYbyGQgQAJVrX6z8/0hozhjAz81G7tuX cVmnC5cw+TgfYspf73yoBLBYZPUY/Ydb7WiabKrSfweMFX848WVhQr7rkwp0DVKQ X0WSbEKrVIGRMCjtvEMkzw1fmXintPLsaoxaLqYZs2MFgEsEP1eEG2MT/2JwpFd/ iDkqVmQ9fPxCEm8beoJXN8HV4Mwz5YY5E04tSqCktJzPh9+sGwB4cPy7PPiPjvHK I8nIdLHtOqFs4SwX1ic6HEZbeBE71swxr5QKhSg3/v6MzjZbK9/IU0RBcY69ftek 3fRJV8/hs8mHhfT7LsvB7XCNOxYq8jD1Bzy4oMJ/3LcAOyTLt1QJzFW4yaRSNGBK 6V/pDSWlghefulZu/aZASMh/IyxuCJRJ0uMVUEi20FeaIs96Bq5QBEInN/1JIYdH Qkek7C6dTrP1EdfbZFRa8+RzYEIDL0XmJFce8oicPZLGbhr/Jg1tZAkcUGr9gaeh z9bOTgAI98z29ZSHm4Bb3rb1WWSJY7BBRAgIDDxZuf34wuVUGWEvJOHRkB2iRa87 d6howw9eqWogVNNYHKYoTQCxEaTe7/PB0wXdWX5+AAZ29C0ETPZFOBYVwh9QLuCD V9WxGutqlXohbTgOk8rERHcUMJLlNblJg/i0tOMDU2Me4Uv+nW8UawEWUJClZiZS 5emSnaCr7UwPS9qUz1n1 =LQs8 -----END PGP SIGNATURE-----
