Re: BETA5: Xen 4.19.2-pre domU crash/don't start

Hi!

Am Donnerstag 20 November 2025 um 18:19:55 +0100, schrieb Roger Pau Monné 20K:
> Don't use nestedhvm, it doesn't work properly.  Does the VM work if
> you disable the nestedhvm option?

I need nestedhvm, since I run GNS3/containerlab and vrnetlab in a Linux
domU. I choose Xen, especially because of this capability. Before that I
used bhyve, but the nested result was painfully slow :-(

Disabling nestedhvm didn't change the outcome, but please see below:

> This seems concerning.  Don't you get more output here that contains
> the instruction stream that failed to emulate?
> 
> Are you using a custom build of SeaBIOS?
> 
> Maybe the newer build of SeaBIOS is broken, possibly a result of the
> update of the default GCC version to use.
> 
> You could try to resort to fetching a build of SeaBIOS from 14.3 ports
> tree, if that makes a difference?  SeaBIOS is just a binary blob, so
> doesn't have any dependency on where it's built.  You could even
> pickup a SeaBIOS blob built on Linux and place it in
> /usr/local/share/seabios/bios.bin.
> 
> > (XEN) d4v0 VMRESUME error: 0x7
> 
> According to the SDM this is:
> 
> "VM entry with invalid control field(s)"
> 
> Which could be caused by the guest attempting to enable the
> virtualization extensions inside the VM, and thus corrupting the VM
> state.
> 
> I haven't checked the control fields dumped below for sanity, because
> it's a pain to do it manually.  We should add an automatic checker in
> Xen that points out the incompatibilities, but alas.
> 
> Let me know if removing `nestedhvm=1` from the xl.cfg file solves the
> issue.  Or attempting to boot with a good know version of SeaBIOS,
> I've uploaded my current SeaBIOS build to:
> 
> https://people.freebsd.org/~royger/bios.bin
> 
> If you want to give it a try.  You should just copy it to
> /usr/local/share/seabios/bios.bin replacing your existing build.

The SeaBIOS binary you provided did the trick:

- - - - - - - - - - 8< - - - - - - - - - -

# xl list
Name                                        ID   Mem VCPUs      State   Time(s)
Domain-0                                     0  8191     8     r-----   42736.7
alpine-containerlab                          8  2039     2     -b----      29.7

- - - - - - - - - - >8 - - - - - - - - - -

Thank you :-)

--
Mit besten Wünschen /
With best wishes,

Manuel Kuklinski