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

[Paolo Bonzini]

On 25/06/2018 21:51, Eduardo Habkost wrote:
>> Before that we should ask what the benefit is in changing the default
>> for qemu-system-*.  Nobody is using it in practice to start QEMU with
>> KVM enabled...
>
> How can you be sure?  If qemu-system-* is installed with KVM
> compiled in, libvirt will probe it using
> "-machine none,accel=kvm:tcg" and run the VM using
> "-machine $MACHINE,accel=kvm".

Right, that needs to be qualified with "without libvirt".

> 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.

BTW, another thing that needs documenting is ABI promises for HAX and
WHPX.  Both do not support -cpu in any meaningful way, at least WHPX
installs a migration blocker.

Paolo