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_capabilities....
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
[1] https://gitlab.com/libvirt/libvirt/-/commit/26cfb1a3cd39d731099ee7d5d1c47b37... [2] https://github.com/virt-manager/virt-manager/blob/33ff193ee9fcfdb74f95d946a1...