Re: [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore

[Paolo Bonzini <pbonzini@redhat.com>]

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.

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