linux-meta-kvm kernel has CPU count capped at 64

[Dagmawi Biru]

The linux-kvm kernel appears to have a hard-coded limit of 64 configured CPUs regardless of what is configured on the hypervisor (LXD/QEMU) side. I believe this includes images in the lxd ubuntu: image remote ( https://cloud-images.ubuntu.com/releases)

This is preventing LXD VMs being configured with more than 64 vCPUs. This is affecting cloud images with this -kvm kernel pre-installed, so 22.04 LTS and below.

If we are unable to fix this in -kvm, then the request here would be to re-generate these images to instead use the -generic or -virtual kernels.

Workaround
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With that said, the workaround is to simply install either the linux-virtual or linux-generic metapackages as they in turn install the generic kernel that does not have this limitation.

Repro
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Configure a 70 cpu VM using the ubuntu:jammy image

$ lxc launch ubuntu:jammy testvm --vm -c limits.memory=12GB -c limits.cpu=70

$ lxc config get testvm limits.cpu
70

$ lxc exec testvm -- nproc
64

[Dagmawi Biru (dagbiru)]

looking at this closer, maybe something resolved with the LXD team

The ubuntu: repo here: https://cloud-images.ubuntu.com/releases/jammy/release/ already has the generic image alongside the -kvm kernel ones

Perhaps maybe LXD can be made to point ubuntu:<release> to these non-kvm builds instead? Not sure if the stock cloud images are going to be compatible with the distorbuild versions though.