CODEWITHSUNDEEP
operating-systemosdevxen
Jan
Jan

Reputation: 51

Use the Xen HYPERVISOR_console_io hypercall

I am trying to make a Unikernel work as a Xen paravirtualized guest. I am currently working on a console driver but cannot get it to print any output. For debugging i would like to use the HYPERVISOR_console_io hypercall.

So i compiled Xen from Source with --enable-debug and debug=y options but i am unable to see any output whatsoever when i use this hypercall.

Can someone explain to me, what i have to do to see the messages i send via this hypercall?

Greetings Jan

Upvotes: 1

Views: 304

Answers (1)

Jan
Jan

Reputation: 51

Okay, so i got this working. I had do add the following lines to my /etc/defaults/grub file:

GRUB_CMDLINE_LINUX="console=tty0 console=hvc0 earlyprintk=xen"
GRUB_CMDLINE_XEN="com1=115200,8n1 console=vga,com1 sync_console"

Then update-grub and reboot. If i connect to a serial console now, i can see the output of my hypercall like this:

xen@xen-001:~$ sudo xl create -c domain_config
Parsing config from domain_config
(d4) Hello!
xen@xen-001:~$ sudo xl destroy 4

Hope this helps someone too :-)

Greetings Jan

Upvotes: 3

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