Re: [RFC PATCH 0/3] generic hypercall support

[Avi Kivity]

Marcelo Tosatti wrote:
> > > Also it would be interesting to see the MMIO comparison with EPT/NPT,
> > > it probably sucks much less than what you're seeing.
> > >   
> > >       
> > Why would NPT improve mmio?  If anything, it would be worse, since the  
> > processor has to do the nested walk.
> >     
>
> I suppose the hardware is much more efficient than walk_addr? There's
> all this kmalloc, spinlock, etc overhead in the fault path.
>   

mmio still has to do a walk_addr, even with npt.  We don't take the mmu 
lock during walk_addr.


--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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