Re: [PATCH v2 02/12] KVM: x86: tag the instructions which are used to write page table

Avi Kivity
2011-08-03T08:09:16Z

On 08/03/2011 09:02 AM, Xiao Guangrong wrote:
> > Note we don't need to actually emulate, just decode, since page_fault can tell us whether a write failed due to page tables or mmio.
> >
>
> This is a interesting feature. If it happens, i will just drop the shadow pages
> and retry these instructions directly.

Note it's a little dangerous. If the guest uses a non-page-table
modifying instruction on the PDE that points to the instruction, then we
will unmap the instruction and go to an infinite loop.

Maybe it's better to emulate if we can't find a fix for that.

One way would be to emulate every 20 instructions; this breaks us out of
the loop but reduces costly emulations to 5%.

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