E820 memory allocation issue on Threadripper platforms

[Patrick Plenefisch <simonpatp@xxxxxxxxx>]

Hi,

I ran into a memory allocation issue, I think. It is the same as https://github.com/QubesOS/qubes-issues/issues/8791 and I saw at the end it was recommended (by marmarek) that the issue reporter forward the issue to this list. I searched the list, but as I didn't see it in the list already, I'm doing that now.

Hardware:
I have an AMD Threadripper 7960X on a ASRock TRX50 WS motherboard. The Qubes reporter had a Threadripper 3970X on an ASUS Prime TRX40-Pro Motherboard. I saw a 3rd issue report of a similar issue on another Threadripper, so I think this may be Threadripper-specific.

Setup:
The QuebesOS reporter was using Qubes Installer.
My install was that I had a fresh install of Debian 12 (no gui), and then did `apt install xen-system-amd64` and rebooted.

The issue:
Any boot of Xen on the hardware results in a halted machine. When monitoring the logs with `vga=,keep`, we get:

(XEN) *** Serial input to DOM0 (type 'CTRL-a' three times to switch input)
(XEN) Freed 644kB init memory
mapping kernel into physical memory
about to get started…
xen hypervisor allocated kernel memory conflicts with E820
(XEN) Hardware Dom0 halted: halting machine

None of the settings I or the Qubes reporter have tried have been able to get past this failure.

I am happy to provide debugging support.

Patrick