[SOLVED] vhost backend has no free memory slots left


Sep 17, 2021
I am facing an issue were I migrated a VM from proxmox 6.4.x to 7.3

1. We implemented a new setup with 3 node cluster of 7.3.
2. Took a backup of the VM on old setup of 6.4
4. Restored the backup snapshot on new setup of 7.3
5. In old setup we had processor type default kvm64 and new we are changing it to host
6. 2 VM are working fine whose memory are equal to or below 8GB but there is one VM with memory: 48GB which is giving an error while starting the VM

ERROR: kvm: -device pc-dimm,id=dimm61,memdev=mem-dimm61,node=1: a used vhost backend has no free memory slots left
TASK ERROR: start failed: QEMU exited with code 1

Kindly help on how should this be resolved on new setup of 7.3. what am I missing here
Last edited:
You could try what is suggested in this post [1] and add the option to it. You will need to reboot for this to take effect:
$ cat /etc/modprobe.d/vhost.conf

options vhost max_mem_regions=509

[1] https://forum.proxmox.com/threads/hotplug-memory-limits-total-memory-to-44gb.30991/#post-499404
@shrdlicka Yup referred and did the exact same thing which got things moving forward for me. Felt like a major block during this migration but luckily found it, implemented it and it works. I just forgot to post here :D


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