Re: CPU hot-plug and RAM hot-add in virtual machines

From: Rainer Duffner <>
Date: Wed, 21 Jul 2021 09:58:46 UTC

> Am 21.07.2021 um 10:53 schrieb Miroslav Lachman <>:
> On 09/07/2021 13:16, Andriy Gapon wrote:
>> On 08/07/2021 00:34, Miroslav Lachman wrote:
>>> The question is simple but I cannot find answer - Does FreeBSD support hot-plug vCPU and hot-add RAM?
>>> Current virtualization platforms support adding CPU cores or additional RAM without the need to reboot the guest OS. Some of our clients need to add additional vCPUs or RAM so often that hot-plug and hot-add will be really useful. If this is not supported on FreeBSD for now, is there any Work In Progress? Or is there a plan to support it?
>> I think that those features are not supported and I haven't heard of any WIP.
> Thank you for your reply. I know nothing about system internals. Is it too much work to implement it or just nobody from developers need it thus nobody write the code? Virtualization is more and more popular these days so I think it will be useful for many users.
> Kind regards
> Miroslav Lachman

My guess is that it’s something that is very much tied to the Linux kernel.

AFAIK, it works on RHEL (and derivatives), and that’s usually a sign that it’s 100% tied to the Linux-kernel.

We have over 20 Vcenters (yeah...) with thousands of VMs and AFAIK, only one customer has ever requested that feature.

Do you really need it that badly?