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

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Message-ID: <4E37EB8E.6080207@redhat.com>
Date:	Tue, 02 Aug 2011 15:20:30 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 02/12] KVM: x86: tag the instructions which are used
 to write page table

On 08/02/2011 02:07 PM, 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

We already have a mechanism for this, the decode tables.  Why not add a 
new flag, PageTable, and set it on all relevant instructions?

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.


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

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