Xen devel - Jul 2008 - getting debug output out of hvmloader and qemu-dm

How do I get the debug output out of hvmloader and qemu-dm?

I have enabled the debug statements in vgabios.c but nothing comes out
in the logs...

Thanks

James

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If it is the *DEBUG* preprocessor flag in vgabios that you enabled, did
you check xen message buffer (xm dmesg) or serial output?

Kamala
> -----Original Message-----
> From: xen-devel-bounces@lists.xensource.com [mailto:xen-devel-
> bounces@lists.xensource.com] On Behalf Of James Harper
> Sent: Wednesday, July 02, 2008 9:07 PM
> To: xen-devel@lists.xensource.com
> Subject: [Xen-devel] getting debug output out of hvmloader and qemu-dm
> 
> How do I get the debug output out of hvmloader and qemu-dm?
> 
> I have enabled the debug statements in vgabios.c but nothing comes out
> in the logs...
> 
> Thanks
> 
> James
> 
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> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
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> If it is the *DEBUG* preprocessor flag in vgabios that you enabled,
did
> you check xen message buffer (xm dmesg) or serial output?
''xm dmesg'' doesn''t show me anything... how might I
look at the serial
output?

Looking at vgabios.c, the ''printf'' function that is used for
debugging
appears to write to port 0xe9, but I can''t see that anything actually
reads that.

James


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hvmloader''s outb to port 0xe9 is intercepted by Xen, and Xen will prink
the messages:
hvm_domain_initialise() ->  register_portio_handler(d, 0xe9, 1,
hvm_print_line);

You can use a debug build Xen, or specify the "guest_loglvl=all"
parameter in grub.conf for Xen to see the messages printked by hvm_print_line().

-- Dexuan


-----Original Message-----
From: xen-devel-bounces@lists.xensource.com
[mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of James Harper
Sent: 2008年7月3日 10:48
To: Kamala Narasimhan; xen-devel@lists.xensource.com
Subject: RE: [Xen-devel] getting debug output out of hvmloader and qemu-dm
> If it is the *DEBUG* preprocessor flag in vgabios that you enabled,
did
> you check xen message buffer (xm dmesg) or serial output?
''xm dmesg'' doesn''t show me anything... how might I
look at the serial
output?

Looking at vgabios.c, the ''printf'' function that is used for
debugging
appears to write to port 0xe9, but I can''t see that anything actually
reads that.

James


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Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel

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I think I have encountered this issue before.  I could be wrong but if
my memory serves me right, I built the hypervisor/tools with debug=y
(apart from setting the vgabios preprocessor flag) and then I got the
output through xm dmesg.

Kamala
> -----Original Message-----
> From: James Harper [mailto:james.harper@bendigoit.com.au]
> Sent: Wednesday, July 02, 2008 10:48 PM
> To: Kamala Narasimhan; xen-devel@lists.xensource.com
> Subject: RE: [Xen-devel] getting debug output out of hvmloader and
qemu-dm
> 
> > If it is the *DEBUG* preprocessor flag in vgabios that you enabled,
> did
> > you check xen message buffer (xm dmesg) or serial output?
> 
> ''xm dmesg'' doesn''t show me anything... how might
I look at the serial
> output?
> 
> Looking at vgabios.c, the ''printf'' function that is used
for debugging
> appears to write to port 0xe9, but I can''t see that anything
actually
> reads that.
> 
> James

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James Harper writes ("[Xen-devel] getting debug output out of hvmloader and
qemu-dm"):
> How do I get the debug output out of hvmloader and qemu-dm?
Others have replied about hvmloader and the BIOS.  qemu-dm runs as a
process in dom0 and writes to a logfile in /var/log/xen, one per
domain.  You can easily recompile it to have more debugging if that''s
helpful; in particular you can get a pretty complete set of register
debugging (very large!) with the three #define''s at the top of vga.c.

I hope that''s helpful.  Good luck and keep up the good work!

Ian.

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