Re: Booting the FreeBSD kernel as an zImage file needs a patch upgrade ?.

[Julien Grall <julien@xxxxxxx>]

Hi,

On 09/01/2024 22:56, Mario Marietto wrote:
> Maybe it works ? Since I see these two processes enabled...but I don't know
> how to use FreeBSD...
Looking at the rest of the discussion, your script start-freebsd 
contains the following lines:
xl create freebsd.cfg
xl console freebsd

From the logs and ...

> # ps ax
> 2606 ?        Ssl    0:00 xl -vvvv create freebsd.cfg
> 2607 pts/0    Sl+    0:00 /usr/lib/xen-4.17/bin/xenconsole 1 --num 0 --type
> pv
... the ps output, it seems that ``xl create`` completed and you have 
the console open. So the freeze you mention is just because your FreeBSD 
guest is not outputting anything.
As mentioned earlier, I don't think a lot of testing has been done for 
32-bit Arm FreeBSD. So it is quite possible that there are some pieces 
of code missing.
The first step is I would suggest to check the FreeBSD kernel was built 
with Xen options.
If they are, then you will need to find out where FreeBSD is stuck (or 
why the console is not enabled). Unfortunately, we don't have any 
support to use GDB on the guest kernel. So you will have to modify 
FreeBSD a bit to check whether it can stuck.
Assuming you have a debug build of the hypervisor, then you can sprinkle 
the FreeBSD boot code with the assembly instruction 'hvc 0xfffc'.
When this is reached, this will issue an hypercall that will print on 
Xen console that the given instruction as reached (the PC will be 
printed). There are other useful 'hvc' call implemented by Xen for low 
level debugging. You can look at do_debug_trap() in Xen code.
I hope this helps.

Cheers,

--
Julien Grall