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[Qemu-devel] windbg and serial

From: Pantelis Koukousoulas
Subject: [Qemu-devel] windbg and serial
Date: Thu, 23 Apr 2009 15:32:39 +0300


I 've been trying to get windbg in one guest to debug a kernel in another guest
through an emulated serial port connection. There are several blog posts and
a few mails to this list and kvm/kvm-devel from people who claim to have made
this functionality to work, yet nothing seems to work for me with
latest qemu git.

What I 've tried:

Start the debuggee guest with -serial tcp:localhost:1234,server
Start the debugger guest with -serial tcp:localhost:1234
(The debuggee has the right options (/debugport, /baudrate) in its boot.ini.)

When the debuggee starts and after the connection of the sockets is done,
both guests start to boot and the debuggee stops in its boot menu. I
'm selecting
the "debug" menu option (to stop the countdown timer).

Then I wait until the debugger boots fully, start windbg, ask it to connect via
com1, baudrate=112500bps and when it says
"waiting to reconnect..." I 'm continuing the debuggee boot process.

At this point I would expect to see something like "Debugger
connection established'
in the debugger guest, yet nothing. It just continues waiting and
after a while windbg
just closes with an "unable to connect" message. At this point the
debuggee continues
boot normally.

I 've verified that the serial connection works by trying
hyperterminal on both guests
and observing each to be able to send/receive text to the other just fine.

The qemu versions tested were current git as of today and also with the patch in
The guests are both winxp sp3 32-bit. The host is 64-bit (kernel/userland) but
hopefully this is not very relevant for qemu.

Has anyone else here managed to make this configuration
(guest XP debugging another guest XP through serial port) work?

I 'd be interested in any ideas on how to achieve that or debug the
problem further.

Thanks in advance,

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