KVM VM (64GB) won't start with memory hotplug enabled


Renowned Member
Jul 1, 2014

This had been asked several times however after extensive search there is still no real answer that would make sense or a formula that I was able to follow to assign memory - sometime it work and sometimes doesn't (guessing!)

up to 48GB works fine after adding this workaround "options vhost max_mem_regions=509" in /etc/modprobe.d/vhost.conf however other configurations shows errors

Below are examples of the errors with 64GB, 96GB, 128GB, 224GB
64GB: TASK ERROR: memory size (65536) must be aligned to 2048 for hotplugging
96GB: TASK ERROR: memory size (98304) must be aligned to 2048 for hotplugging
128GB: TASK ERROR: memory size (131072) must be aligned to 4096 for hotplugging
132GB: TASK ERROR: memory size (135168) must be aligned to 4096 for hotplugging

Tested with and without Baloon settings...

I also tried @fabian suggestion for 64GB and adding 1G extra works however I can't have a consistent way to apply other variations - for example, 58GB or 50GB, 66Gb etc..

Below are some details and thanks in advance

Reference threads :


Bugs reported:

Server details:


pveversion -v
proxmox-ve: 6.4-1 (running kernel: 5.4.114-1-pve)
pve-manager: 6.4-6 (running version: 6.4-6/be2fa32c)
pve-kernel-5.4: 6.4-2
pve-kernel-helper: 6.4-2
pve-kernel-5.4.114-1-pve: 5.4.114-1
pve-kernel-5.4.106-1-pve: 5.4.106-1
ceph: 15.2.11-pve1
ceph-fuse: 15.2.11-pve1
corosync: 3.1.2-pve1
criu: 3.11-3
glusterfs-client: 5.5-3
ifupdown: residual config
ifupdown2: 3.0.0-1+pve3
ksmtuned: 4.20150325+b1
libjs-extjs: 6.0.1-10
libknet1: 1.20-pve1
libproxmox-acme-perl: 1.1.0
libproxmox-backup-qemu0: 1.0.3-1
libpve-access-control: 6.4-1
libpve-apiclient-perl: 3.1-3
libpve-common-perl: 6.4-3
libpve-guest-common-perl: 3.1-5
libpve-http-server-perl: 3.2-2
libpve-network-perl: 0.6.0
libpve-storage-perl: 6.4-1
libqb0: 1.0.5-1
libspice-server1: 0.14.2-4~pve6+1
lvm2: 2.03.02-pve4
lxc-pve: 4.0.6-2
lxcfs: 4.0.6-pve1
novnc-pve: 1.1.0-1
proxmox-backup-client: 1.1.6-2
proxmox-mini-journalreader: 1.1-1
proxmox-widget-toolkit: 2.5-5
pve-cluster: 6.4-1
pve-container: 3.3-5
pve-docs: 6.4-2
pve-edk2-firmware: 2.20200531-1
pve-firewall: 4.1-3
pve-firmware: 3.2-3
pve-ha-manager: 3.1-1
pve-i18n: 2.3-1
pve-qemu-kvm: 5.2.0-6
pve-xtermjs: 4.7.0-3
qemu-server: 6.4-2
smartmontools: 7.2-pve2
spiceterm: 3.1-1
vncterm: 1.6-2
zfsutils-linux: 2.0.4-pve1


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