Public bug reported:
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
---
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
---
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
** Affects: lxd
Importance: Undecided
Status: New
** Affects: linux-meta-kvm (Ubuntu)
Importance: Undecided
Status: New
** Also affects: lxd
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2067777
Title:
linux-meta-kvm kernel has CPU count capped at 64
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