Paolo Bonzini <pbonz...@redhat.com> writes: > On 22/06/2018 21:35, Eduardo Habkost wrote: >>>> Why is this better than using KVM by default if it's available? >>> The answer is (as almost always): Compatibility with migration. Nobody >>> dares to sacrifice that chicken :-( >> We can now kill it if we announce the feature as deprecated a >> couple of releases in advance. >> >> If we declare that compatibility when the accelerator is omitted >> is deprecated in 3.0, in QEMU 3.3 we will be free to choose a >> different default accelerator. > > We can, we don't necessarily want it. > > The status quo is that people using KVM are invoking qemu as qemu-kvm, > people using TCG are invoking qemu as qemu-system-*. All distros are > shipping a qemu-kvm or more rarely kvm binary, which is invariably a > wrapper script except for RHEL because RHEL doesn't have a qemu-system-* > binary at all. > > By the way, changing qemu-system-*'s default to e.g. RHEL's "kvm or tcg" > would not help distros that have "-accel kvm" in their /usr/bin/qemu-kvm > script.
It wouldn't hurt them, either. Attentive distros could even replace the wrapper script by a link. > All in all, it seems simpler for me to take the status quo, which is > what non-RHEL distros do, and make it part of upstream. > > Paolo
