Xen devel - May 2009 - Clarification Guest Paging Table WriteProtection

Hi,

    I am new to Xen and trying to understand how Shadow Paging works. I
require
clarification on following point:

 

How does Xen write protect guest page table? 

What I could understand reading code & other sources is that, when ever
cr3 gets
updated, control gets transferred to the hypervisor which then does the
emulation for the instruction and write protects the guest page table.
But the
confusion is, cr3 contains Pseudo-physical address of the guest page
table, but
to protect this page protection bit is required to be set in its page
table
entry. How does Xen get page table entry for the address in cr3?

 

Thanks in advance,

Dang

 



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