Am 03.04.2012 21:38, schrieb Anthony Liguori: > Right now, '-M pc' is the default and, in general, this machine type has guest > visible ABI changes in each version of QEMU. At some point in each release, > we create a '-M pc-X.Y' corresponding to the last release and attempt to make > that look like the previous QEMU version's machine. > > We've accumulated a bunch of '-M pc-X.Y's at this point and if we move to a > three month release process, the problem will get much worse. > > This is a proposal to change the way we do things in order to simplify > compatibility and present a very clear statement of what we support. > > With this patch, we will not introduce any more '-M pc-1.x' beyond 'pc-1.0'. > We will not introduce a new 'pc-X.Y' until the QEMU 2.0 release (1Q 2014). > Instead, we will introduce a 'pc-next' machine type that is *not* the default > machine type. If you omit a '-M' option, you will get '-M pc-1.0'. However, > if you want to test the latest and greatest, you will need to use an explicit > '-M pc-next'.
Independent of what frequency of machine versions we offer, I think defaulting to pc-1.0 is a bad idea. The people fiddling with QEMU command lines are mostly developers, others can be expected to use a more convenient frontend, such as libvirt or oVirt. I would hope that updating any of these frontends to supply a -M pc-1.0 argument would be possible without much effort. Expecting developers to type -M pc-next again and again will result in pc-next not being tested as much and thus broken quickly. Therefore I would suggest to make pc-next the default machine but to alias pc-1.0 as "pc", if we want to split off pc-next from pc-x.y. Being the one who commented on the shortened release cycle causing new machines to emerge each release, I was rather thinking of widening the release cycle again. But rather than talking about time periods, maybe we should compile a time table of when distributions actually choose a new QEMU version? Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg