Re: CR3 Virtual Address

[Mats Petersson <mats.petersson@citrix.com>]

On 28/11/12 14:48, emdel wrote:
> Hello everybody,
>
> I have to work with the Xen 4.2 memory management code for a research
> project and I have some questions.
>
> 1) Since I have to change and/or remove some entries in the hypervisor
>    page table, I would like to know the "virtual address" of the CR3
>    register.
As per Andy Cooper's answer, but further:
Exactly (or at least roughly) what are you trying to achieve?
You want to "remove" some memory from the hypervisor itself? Who/what 
will use this memory?
It is MUCH easier to advice on HOW to do something if we understand what 
you are actually trying to do.
>
> 2) I would also like to know if the VMCS virtual address is mapped 
> inside the
>    page table pointed by the HOST_CR3.
The "HOST_CR3" is the Xen (VCPU's) true CR3 (for the "host" or "root" 
mode, as Intel calls it - this is the hypervisor itself). it is set from 
vcpu.arch.cr3. So the VMCS is available here, or the system would crash 
when it returns from guest operation.
>
> 3) Are there functions to perform the page walking on the hypervisor
>    page tables?
Yes. As per Andy Cooper's answer.

--
Mats
>
>
> Thank you for the attention,
>
>
> Best Regards.