Re: [Qemu-devel] [PATCH V3] Support logging xen-guest console

[Chun Yan Liu]

On Thursday, June 30, 2011 07:18:54 PM you wrote:
> On 06/30/2011 11:39 AM, Chun Yan Liu wrote:
> > On Thursday, June 30, 2011 03:58:57 PM Alexander Graf wrote:
> >> On 30.06.2011, at 09:08, Chunyan Liu wrote:
> >>> Add code to support logging xen-domU console, as what xenconsoled does.
> >>> To enable logging, set environment variable XENCONSOLED_TRACE=guest and
> >>> XENCONSOLED_LOGDIR=<specified directory>, log file will be saved in
> >>> <specified directory>.
> >> 
> >> In fact, this whole thing looks as if you're merely trying to
> >> reimplement "tee" on the xenconsole output. Wouldn't it make more sense
> >> to do this in
> >> 
> >> the char layer? So we could do:
> >>    -xenconsole tee:stdio,file:/tmp/xen.log
> >> 
> >> or similar? That's probably a lot more useful than a random Xen specific
> >> hack.
> > 
> > Thanks, Alex.  It IS something like "tee". But IMO, change in
> > xen_console.c and change in char layer are just different time points,
> > do not have essential difference. Change in xen_console.c is trying to
> > backup output data into log file before sending to char device, change
> > in char device is trying to dupicate data from char device to log file.
> > Correct me if I'm wrong.
> 
> Sure, the outcome is the same though, no? We get the output data in both
> a file and the char backend.
>  
Char device in qemu is not only used by console. Compared with the benefits 
that brings, I still doubt if it is proper to adding this functionality to 
char layer.  
Stefano, how do you think?

Thanks,
Chunyan