Re: [Xen-devel] ioport 0x12 logfile writing

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxx] On Behalf Of James Harper
> Sent: 24 December 2013 06:28
> To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Subject: [Xen-devel] ioport 0x12 logfile writing
> 
> Under xen 4.1 and the old qemu I could write to /var/log/xen/qemu-dm-
> <domu name>.log from inside the vm by writing to ioport 0x12. Is that
> functionality replaced in any way in qemu upstream? Does qemu have its
> own logging mechanism?
> 

That logging mechanism (via qemu tracing: see 
http://repo.or.cz/w/qemu/stefanha.git/blob_plain/refs/heads/tracing:/docs/tracing.txt)
 is still there, but unfortunately off by default. I think recent xen builds 
now compile upstream qemu with a stderr trace backend by default at least so 
all you should need to do is create a events file by doing:

Echo xen_platform_log > /tmp/events

And then adding "-trace events=/tmp/events" to your qemu command line via your 
xl.cfg:

device_model_args = ['-trace', 'events=/tmp/events']

Port 0x12 logging should then appear as before.

  Paul




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