Re: pv_ops dom0 and kernel console output problem

[Jeremy Fitzhardinge <jeremy@goop.org>]

Pasi Kärkkäinen wrote:
> Reading pv_ops wiki page I noticed this:
>
> "If the domain crashes very early, before any output appears on the console,
> then booting with: "earlyprintk=xen" should provide some useful information.
> If you are running a debug build of Xen hypervisor (set "debug = y" in
> Config.mk in the Xen source tree), then you should get crash dumps on the
> Xen console. You can view those with "xm dmesg"."
>
> So I guess earlyprintk=xen is only useful if you're running debug build of
> Xen hypervisor.. ?

earlyprintk=xen has the effect of directing the kernel's console output 
via the console output hypercall.  domU kernel's are not generally 
allowed to do this, but it is when you compile Xen in debug mode.  dom0, 
however, uses the Xen console in the normal case, so it doesn't need a 
debug Xen build.  But when Xen switches its console output to serial the 
kernel's output goes with it, so if you want it to appear on VGA you 
need to use the VGA console output (make sure your kernel has all the VT 
console options enabled).

    J