Re: [PATCH] kvm-vmx: add module parameter to avoid trapping HLT instructions (v2)

Gleb Natapov
2010-12-06T14:14:54Z

On Mon, Dec 06, 2010 at 08:08:08AM -0600, Anthony Liguori wrote:
> On 12/06/2010 08:02 AM, Avi Kivity wrote:
> >On 12/06/2010 04:01 PM, Avi Kivity wrote:
> >>>It's not just possible, it appears to be exactly what happens.
> >>>
> >>>I guess it makes sense that RIP gets advanced before HLT
> >>>begins to wait.
> >>>
> >>
> >>
> >>It does. Good, it simplifies the patch.
> >>
> >
> >btw, this is how kvm emulates HLT - first we advance rip, then we
> >sleep the vcpu.
>
> Yes, I assume the hardware updates RIP immediately after fetching
> the instruction. That's at least how some simpler architectures I'm
> aware of work.
>
By "simpler" you mean "saner"? x86 needs at least decode it before
updating RIP :)

--
Gleb.