On Fri, Mar 23, 2018 at 04:48:27PM -0300, Eduardo Habkost wrote: > On Fri, Mar 23, 2018 at 12:45:30PM +0300, Roman Kagan wrote: > > On Thu, Mar 22, 2018 at 03:38:13PM -0300, Eduardo Habkost wrote: > > > It looks like the guest can still crash if we migrate > > > "QEMU-2.12 -machine pc-2.11 -cpu ...,+hv-time" to a host running > > > QEMU 2.11 and Linux < 4.14. > > > > Indeed :( > > Well, your patch fixes it by not enabling hv-frequencies by > default on any machine-type. Do you see any gotchas?
Only the need to add a new property in -stable. I used to think that was frowned upon. > > So, taking the effort/complexity vs safety tradeoff into account, we can > > consider an alternative approach: just add hv_frequencies (default=off) > > cpu property to 2.12 and 2.11-stable, and ignore the cases where it's > > run on QEMU versions without explicit control over this feature. Would > > it be too much against the current policy? > > > > With this, we can just declare that QEMU v2.11.0 + Linux 4.14+ > was broken, and advise people to upgrade QEMU. > > I think is the most reasonable option we have. See my reply to > the patch you sent. Great, let's try going down this route. Thanks, Roman.
