Performance CPU flags - CPU host

[Giggling3999]

I have a Ryzen 5600x.

Is there any CPU flags I can pass that improve performance ? I am currently passing through host model

I am not particularly concerned with the security implication

 

[BobhWasatch]

Host is the actual host CPU. That passes all the feature flags that the host supports.

 

[Giggling3999]

It wont turn off a mitigation for the guest regardless?

 

[BobhWasatch]

You can only turn off mitigations on the whole machine, not per-guest.

 

[Giggling3999]

Is this the case even for non 'host' models ? I've heard that host is fastest anyway, so presumably that negates the point

 

[BobhWasatch]

Host is generally the fastest. The CPU type can't create new features, it only masks or unmasks the ones the real host CPU supports. Mitigations on/off is a separate thing that applies to the host kernel.

Turning mitigations off on the host might speed the whole thing up significantly, or not, depending on the CPU. I don't know how it affects yours, you would have to try it and see. It is done by passing "mitigations=off" on the kernel command line. How you do that depends on which bootloader you are using. See post #2 in this thread:

https://forum.proxmox.com/threads/p...w-performance-for-windows-server-2022.150849/