On 26/06/2018 14:29, Eduardo Habkost wrote: > On Tue, Jun 26, 2018 at 07:57:18AM +0200, Paolo Bonzini wrote: >> On 25/06/2018 21:51, Eduardo Habkost wrote: >>> In either case, I'm not arguing (yet) for changing the default >>> upstream. I'm just arguing for upstream QEMU to not make any >>> promises about the default. >> >> It would be a guest ABI breakage for TCG guests, so it would only apply >> to new machine types. I don't think it's worth the complication. > > That's exactly the point: I want to stop promising a stable guest > ABI when the accelerator is omitted, because I see no benefit in > wasting energy on this.
On the other hand I see no benefit in changing a default that people are obviously not using (since most people use KVM, not TCG). Distros will keep shipping, and people will keep using qemu-kvm even if we change the default. > (I don't think we ever kept the guest ABI correctly with TCG, by > the way.) It would not be any different from KVM. Less tested and likely to be more buggy, yes, but not particularly harder. Paolo