Re: [PATCH] [RESEND] x86_64: add memory hotremove config option

[Andi Kleen <andi@firstfloor.org>]

> Sorry, by "block", I really mean spin I guess. I mean that the CPU will
> be forced to stop executing due to the page fault during this sequence:

It's hard for NMIs at least. They cannot execute faults.

In the end you would need to define a core kernel which 
cannot be remapped and the rest which can and you end up
with even more micro kernel like mess.

> ptep_clear_flush(ptep)         <--- from here
> set_pte(ptep, newpte)          <--- until here
> 
> for prot RW, the window also would include the memcpy, however if that
> adds too much latency for execute/reads, then it can be mapped RO first,
> then memcpy, then flushed and switched.
>  
> 
> > Then that would be essentially a hypervisor or micro kernel approach.
> 
> What would be? Blocking in interrupts? Or non-linear kernel mapping in

Well in general someone remapping all the memory beyond you.
That's essentially a hypervisor in my book.

-Andi