RE: [Xen-devel] debug logging in windows

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> > Windows makes internal 'debugprint' calls, kind of like the kernel
> > logging that Linux does that you get via dmesg.
> >
> > It would make my life a heap easier if I could route those to dom0.
The
> > windows debugger allows this indirectly but it is really slow and
has
> > heaps of overhead.
> >
> > Is it possible to use the /local/domain/<id>/drivers/console/0 to do
> > this? It looks like even PV linux doesn't use this, so maybe it's
just a
> > legacy thing?
> If you boot your hypervisor with guest_loglvl=all on the command line
> then you should be able to log to Xen's ring buffer by outb'ing bytes
> to port 0xe9.  The results will show up in xm dmesg and the hypervisor
> serial console.
> 
> I'm not sure what version of Xen you're running, but some of the older
> ones had problems with rep outsb to that port, so you might be better
> off using a bunch of individual outb's.
> 

That's interesting... so that is implemented by the hypervisor then?

Is there something similar implemented via hvm/qemu that can log via hvm
log files? That would make life easier. If not, I'll implement it.

Currently, 'xm save' appears to work but after 'xm restore' the DomU is
hanging at some really strange points (eg between one KdPrint statement
and the next), so I suspect that something else is going on but I'm
never getting the debug output because it's crashed so hard that even
the windows debugger can't talk to me anymore. At least if I was doing
outb's the logging would be done synchronously and I wouldn't have the
debugger connected which I think is introducing a heisenbug effect...

Thanks

James

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