On Mon, Jul 09, 2012 at 04:34:50PM +0300, Avi Kivity wrote:
> On 07/09/2012 04:23 PM, Xiao Guangrong wrote:
> > On 07/09/2012 08:49 PM, Avi Kivity wrote:
> >> On 07/09/2012 02:23 PM, Gleb Natapov wrote:
> >>>
> >>>> kvm-unit-tests.git has a test for xchg to mmio. Does it still work?
> >>>>
> >>>> I agree this code has to go, but it needs to be replaced by something.
> >>>> Maybe a .valid flag in struct operand.
> >>>>
> >>> Valid will not enough for that.
> >>
> >> If we make everything go through operands, any reason why not?
> >>
> >
> > I noticed some instructions need to read ESP for many times (e.g,
> > iret_real),
> > maybe .valid flag is not enough for this case if the stack is in MMIO, yes?
>
> Good catch. We either have to fix it or to restrict stack operations to
> regular memory (->read_std).
>
> > IIUC, I also noticed ESP is not reset back if it is emulated fail (mmio is
> > needed).
> > If the stack located in mmio region, this kind of instruct will be broken,
> > i know no
> > guest will use mmio as stack but SDM does not limit it, is it valid?
>
> Stack in mmio (or task switch in mmio) is architecturally valid. We
> don't have to support it if no guests do it.
>
But the code is already here, why drop it?
--
Gleb.
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