[Xen-devel] RE: EPT walks for guest page table

["Nakajima, Jun" <jun.nakajima@xxxxxxxxx>]

Even if the guest wants to read data or execute code, the guest page table may need to be modified for the processor to set the A bit when running with paging enabled. This means NPT or EPT needs to set the W permission for the guest page table pages to avoid VM exits or EPT violation. Depending on the implementation, the A bit may need to be set upfront even if the translation turns to be invalid.

 

Thanks,

Jun
---
Intel Open Source Technology Center

From: bo ma [mailto:kyle.ma83@xxxxxxxxx]
Sent: Monday, November 24, 2008 1:37 AM
To: xen-devel@xxxxxxxxxxxxxxxxxxx
Cc: Nakajima, Jun; Xin, Xiaohui
Subject: EPT walks for guest page table

 

Hi,

I am really confused about  NPT walks for guest page table , and  eager to know the details about it.
It is  treated as data writes even if the access itself is a code read in AMD NPT.I just want to know : is it the same in EPT?

Could anyone help me? I would like to know that very much

Thank you in advance

 

Bo Ma

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