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[Xen-devel] Question about mapping between domU's Physical Memory and Xen's Machine Memory


  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: "Haifeng He" <hehaifeng2nd@xxxxxxxxx>
  • Date: Mon, 5 Nov 2007 14:35:09 -0700
  • Delivery-date: Mon, 05 Nov 2007 13:35:46 -0800
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  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

Hi,

I am trying to understand the process of setting up the Physical-Machine mapping
between domU and Xen during domain building. If I understand correctly,
the process involves:

1. the linear address of OS kernel for domU first maps to the physical pages
in domU. For example, address 0xc0100000 -> physical page 0x100.

2. Each physical page frame in domU is assigned a machine frame number in Xen.
for example, physical page 0x100 -> machine page 0x1856.

3. Setup domU page table for the first mapping (1.).

4. Setup Phys-Mach mapping table for the second mapping (2.)

My question is, if we only talk about the mapping for domU's kernel
address (suppose OS kernel is Linux), will the two mappings mentioned
above (1. and 2.)
be modified later after domU is booted?

In the above example, will kernel address 0xc0100000 always be mapped
to physical page 0x100 and will physical page 0x100 be always mapped
to machine page 0x1856? If not, what may cause the changes?

Another question, how does Xen assign machine frame number to domU's
physical page?

Thanks

Haifeng

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