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Aligning Xen to physical memory maps on embedded systems

  • To: "Xen-users@xxxxxxxxxxxxxxxxxxxx" <Xen-users@xxxxxxxxxxxxxxxxxxxx>
  • From: Levenglick Dov <Dov.Levenglick@xxxxxxxxxxxxxxxx>
  • Date: Sun, 21 Feb 2021 16:30:29 +0000
  • Accept-language: en-US
  • Delivery-date: Sun, 21 Feb 2021 16:31:24 +0000
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  • List-id: Xen user discussion <xen-users.lists.xenproject.org>
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  • Thread-topic: Aligning Xen to physical memory maps on embedded systems


I am booting True Dom0-less on Xilinx ZynqMP UltraScale+ using Xen 4.11,
taken from https://github.com/Xilinx/xen.

The system has 2GB of RAM (0x00000000 - 0x80000000) of which Xen and the DomU 
have an allocation of 1.25GB, per this memory map:
1. DomU1: 0x60000000 - 0x80000000
2. DomU2: 0x40000000 - 0x60000000
3. Xen: 0x30000000 - 0x40000000

I am able to support True Dom0-less by means of the patch/hack demonstrated
By Stefano Stabellini at https://youtu.be/UfiP9eAV0WA?t=1746.

I was able to forcefully put the Xen binary at the address range immediately
below 0x40000000 by means of modifying get_xen_paddr() - in itself an ugly hack.

My questions are:
1. Since Xen performs runtime allocations from its heap, it is allocating
   downwards from 0x80000000 - thereby "stealing" memory from DomU1.
   Can I force the runtime allocations to be from a specific address range?
2. Has the issue of physical memory map address maps been addressed by Xen for 

Thank you.
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