RE: [Xen-devel] debug logging in windows

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

> 
> > 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.
> There isn't at the moment, at least not in the xenbits repositories.
> There is one in the XenServer version of qemu, though.  I've attached
> the relevant patch.  If you apply this and rebuild qemu then you
> should be able to send stuff to the qemu logfile by writing bytes to
> port 0x12.  Note that this is rate limited, though, and if you hit the
> limiter the domain will be quite severely punished.
> 
> I've checked that this applies against qemu-xen-unstable.git, and that
> the resulting tree at least builds, but I've not actually checked that
> it works.  Upstream qemu is pretty similar to XenServer qemu at the
> moment, though, so it should be okay.

I'll have a look at that one. I have actually just implemented the same
sort of thing but trapping writes to the platform pci io space. It's
just for debugging so I haven't done rate limiting or anything.

A port 0x12 debugger would be better as I could log stuff even before
the Xen PCI ioport range is mapped.

> 
> > 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...
> Can't help you with that, sorry.
> 

Well hopefully you have :)

Thanks

James

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