Re: [External] Re: [RFC 0/5] parker: PARtitioned KERnel

[H. Peter Anvin]

On 2025-09-25 00:26, Fam Zheng wrote:
>> From: "H. Peter Anvin"<hpa@xxxxxxxxx>
>> The difference is that this is highly invasive to the OS, which affects developers and users not wanting this feature.
> 
> Yeah that makes sense, thanks for clarifying. By having a hypervisor
> at least in early boot of secondary kernels, we don't need to patch
> device enumeration etc. In the kernel code.
> 
> Once the kernel is up, it can be then promoted to run directly on bare
> metal, so zero performance overhead.

Realistically you would remain in the hypervisor, but nothing or almost
nothing will trap into the hypervisor, so again, zero or negligible
performance overhead.  You also *can* put some isolation or protection
features in the low-level hypervisor.

The important thing here is that the maintenance burden *and* the policy
choices fall on the users of the feature, and as the upstream maintainers
cannot and thus will not test this use case, it is likely to break on a
regular basis.

This is basically "paravirt_ops all over again." There are very good reasons
we are trying to get rid of them.

	-hpa