Re: [PATCH 02/11] KVM: x86: tag the instructions which are used to write page table

Avi Kivity
2011-08-22T14:36:43Z

On 08/22/2011 05:32 PM, Marcelo Tosatti wrote:
> On Tue, Aug 16, 2011 at 02:41:27PM +0800, Xiao Guangrong wrote:
> > The idea is from Avi:
> > | tag instructions that are typically used to modify the page tables, and
> > | drop shadow if any other instruction is used.
> > | The list would include, I'd guess, and, or, bts, btc, mov, xchg, cmpxchg,
> > | and cmpxchg8b.
> >
> > This patch is used to tag the instructions and in the later path, shadow page
> > is dropped if it is written by other instructions
>
> What is the advantage of doing this again? What is the point of
> dropping shadow if the instruction is emulated?
>

So it won't be emulated again; the assumption is that if you addl into a
page, it isn't a pagetable.

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error compiling committee.c: too many arguments to function