RE: [RFC PATCH v1 1/5] x86/boot: Shift VMXON from KVM init to CPU startup phase

Huang, Kai
2025-09-10T20:52:46Z

> > Since I think doing VMXON when bringing up CPU unconditionally is a
> > dramatic move at this stage, I was actually thinking we don't do VMXON
> > in CPUHP callback, but only do prepare things like sanity check and
> > VMXON region setup etc. If anything fails, we refuse to online CPU,
> > or mark CPU as VMX not supported, whatever.
>
> the whole point is to always vmxon -- and simplify all the complexity from doing
> this dynamic.
> So yes "dramatic" maybe but needed -- especially as things like TDX and TDX
> connect need vmxon to be enabled outside of KVM context.
>
>
> >
> > The core kernel then provides two APIs to do VMXON/VMXOFF
> > respectively, and KVM can use them. The APIs needs to handle
> > concurrent requests from multiple users, though. VMCLEAR could still
> > be in KVM since this is kinda KVM's internal on how to manage vCPUs.
> >
> > Does this make sense?
>
> not to me -- the whole point is to not having this dynamic thing

Sure. Fine to me to just always on.