Problem activating Memory Hotplug

[Baader-IT]

Hi,

we have a problem activating memory hotplug on 7 vm's running on a 14 Node V6.1-7 Cluster.
These VM's have either 32GB, 97GB or 141GB Ram assigned.
When Memory hotplug is activated on these VM's the following message shows when trying to boot:

kvm: -device pc-dimm,id=dimm61,memdev=mem-dimm61,node=1: a used vhost backend has no free memory slots left

Every Node has 378GB Ram and without Memory Hotplug the VM's are booting and running fine.

Regards
Frank

 

[Alwin]

Maybe this thread may help.
https://forum.proxmox.com/threads/hotplug-memory-limits-total-memory-to-44gb.30991/post-154914

 

[Baader-IT]

cat /sys/module/vhost/parameters/max_mem_regions
64

referring to this thread this limit should not be 64 anymore in PVE.
is there a reason why 64 is the default and what exactly does this parameter do ?
is this parameter a size limit for memory hotplug ?

 

[Baader-IT]

looks like there was a lot of discussion about this issue in 2016:

https://pve.proxmox.com/pipermail/pve-devel/2016-December/024488.html

 

[Gilberto Ferreira]

I have face the exactly some problem now in 2022!!!
Why this issue still exist in PVE?????
So weird.

 

[Matyi.Szabolcs]

Hi!

The problem is still there in Proxmox 7.2-11
If the memory hotplug is activated, I get a kernel panic after a reboot.
The problem does not occur with Ubuntu VM, only with Almalinux and Rockylinux.
I tried several kernel versions, but there was a kernel panic with all of them.

I also often encounter such errors:
TASK ERROR: memory size (65536) must be aligned to 2048 for hotplugging

Thanks!