On Tue, Aug 13, 2013 at 05:11:08PM +0200, Andreas Färber wrote: > Am 13.08.2013 16:54, schrieb Paolo Bonzini: > > Il 13/08/2013 16:11, Anthony Liguori ha scritto: > >>>> Fix this up, clean up a trivial code duplication > >>>> and add a comment explaining why we special-case 1.5 > >>>> with respect to pvpanic. > >>>> > >>>> Reported-by: Markus Armbruster <arm...@redhat.com> > >>>> Signed-off-by: Michael S. Tsirkin <m...@redhat.com> > >> Thanks for catching this. I'm a little disturbed by this. I use git-am > >> --3way specifically to avoid problems from fuzzing but I guess merge > >> artifacts are possible. > >> > > > > I wonder if we shouldn't disable pvpanic in 1.5 too, one-off behavior is > > ugly and likely no one will notice. > > I had rejected the previous attempt to completely disable pvpanic device > because it looked to me as if this compatibility aspect had been > forgotten. I didn't imagine the resulting code to look as ugly though, > with us "skipping" _1_5 to not have 1.5 overwrite has_pvpanic for 1.6+. > > mst suggested to patch stable-1.5 to disable it there, too. I am not > against but have doubts as to how well that works with migration, since > 1.5.3 is still a bit off and I would expect 1.5.2 -> 1.6.0 migration to > work without guest-visible changes... We could argue that having to use > -M pc-i440fx-1.5 we can also expect users to add -device pvpanic; > question would be how to convey that knowledge of > if-you-use-pc-x.y-then-you-also-need-to-do-Z to users, which > compat_props usually handle under the hood. We could misuse > pvpanic.ioport=0 for that purpose until we have a better solution. > > Regards, > Andreas
Well, in this case then this boils down to 1.5.2 migration being buggy - having a small race (migration during reset) which we can then close with 1.5.3 . I don't think anyone ever triggered this race in practice so I'm not sure whether we should be too worried about this. > -- > SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany > GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg