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

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Message-ID: <4E526975.4080106@redhat.com>
Date:	Mon, 22 Aug 2011 17:36:37 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Marcelo Tosatti <mtosatti@...hat.com>
CC:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 02/11] KVM: x86: tag the instructions which are used to
 write page table

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.

-- 
error compiling committee.c: too many arguments to function

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