Re: Improve default machine type selection
On 3/14/23 11:24, Andrea Bolognani wrote:
On Mon, Mar 13, 2023 at 02:25:01PM -0600, Jim Fehlig wrote:
> If an explicit machine type is not specified in the VM config, the qemu
> driver will select the first machine type in the list of machine types for
> the specified accelerator. See virQEMUCapsGetPreferredMachine
>
> https://gitlab.com/libvirt/libvirt/-/blob/master/src/qemu/qemu_capabiliti...
>
> On my test machines, this works reasonably well for x86_64 where the first
> machine type is pc-i440fx-7.1. But for aarch64, the first machine is
> integratorcp, which is not very useful with maxCpus=1 and other limitations.
What you're describing is the historical behavior, but these days
it's a bit more complicated than that: we actually go out of our way
to make sure that the default machine for an architecture is the one
that QEMU *originally* listed first. See [1] for the implementation
as well as the rationale.
Ah, thanks. Facepalm for missing that...
> Would it be possible to select a "better" default
machine type? E.g. 'pc'
> for x86_64, 'virt' for aarch64, etc. I'm happy to work on this if folks
deem
> it's a reasonable improvement. It would benefit tools like the libvirt
> terraform provider, which prefer to use something more generic like
> <type>hvm</type>.
As much as I would *love* for virt to be the default aarch64 (and
riscv64) machine type, unfortunately our strong backwards
compatibility guarantees prevent us from changing this :(
Yep, understood.
On the plus side, at least implementing more reasonable defaults at
the application level should be quite straightforward. See [2] for
virt-manager's take.
Nice! Thanks again for the details.
Regards,
Jim