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Re: [Xen-devel] CR3 Virtual Address

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
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.


Thank you for the attention,

Best Regards.

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