Re: [Xen-devel] CR3 Virtual Address

[emdel <emdel@xxxxxxxxxxxx>]

On Wed, Nov 28, 2012 at 4:06 PM, Mats Petersson <mats.petersson@xxxxxxxxxx> wrote:

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.

For my project I'm trying to dump all physical memory of the machine from
hypervisor layer so I can get access to all physical memory. Then when I
obtained the dump of the physical pages I want to find out the VMCS structures
of the running guests. In order to do that I was thinking that I can insert an entry
into a HV page table that maps an arbitrary virtual address into a determine
physical address. By using this trick I should be able to map all the physical
memory address and read/dump it by reading the virtual address.

So following this solution my problem now is to find out the virtual address of
the page directory pointer table (pae address mode 32 bits).

 

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.

Ok, perfect.

 

3) Are there functions to perform the page walking on the hypervisor
   page tables?

Yes. As per Andy Cooper's answer.

Actually we would like to know if there are any functions for mapping a
physical page into a virtual page. Could you please point me out in more
precisely way to the name of those functions?  I'm working with pae address
mode 32 bits.


Thanks
 

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