Re: [Qemu-devel] [RFC PATCH] hw/s390x: Allow to configure the consoles with the "-serial" parameter

[Cornelia Huck]

On Tue, 24 Apr 2018 16:02:59 +0200
Thomas Huth <address@hidden> wrote:

> On 24.04.2018 13:49, Christian Borntraeger wrote:
> > 
> > 
> > On 04/24/2018 01:44 PM, Thomas Huth wrote:  
> >> The consoles ("sclpconsole" and "sclplmconsole") can only be configured
> >> with "-device" and "-chardev" so far. Other machines use the convenience
> >> option "-serial" to configure the default consoles, too, even for virtual
> >> consoles like spapr-vty on the pseries machine. So let's support this
> >> option on s390x, too, so we can easily enable the serial console here
> >> again with "-nodefaults", for example. Also map the second -serial
> >> option to the "sclplmconsole", so that there is now an easy way to
> >> configure this second console on s390x, too.
> >> Additionally, the new code is also smaller than the old one and we have
> >> less s390x-specific code in vl.c :-)  
> > 
> > Can you show some new example command lines?  
> 
> Sure. I'm mainly using this together with nodefaults:
> 
> qemu-system-s390x -no-shutdown -nographic -nodefaults -serial mon:stdio
> 
> That's way easier than typing:
> 
> qemu-system-s390x -no-shutdown -nographic -nodefaults \
>   -chardev stdio,id=c1,mux=on -device sclpconsole,chardev=c1 \
>   -mon chardev=c1

What, you don't like typing complicated command lines? :)

> 
> Another example: You only want to see the QEMU monitor on stdio, but not
> the serial output, without using -nodefaults (i.e. you still want to
> have the other default devices). AFAIK that's pretty impossible with the
> current code. But once you've got this patch applied, you can do:
> 
> qemu-system-s390x -no-shutdown -nographic -serial none
> 
> And to view the sclplm console, you can now simply do:
> 
> qemu-system-s390x -no-shutdown -nographic -serial null -serial mon:stdio

Looks cool. Maybe add some of the examples to the patch description?

> 
> > I read that as "the current command lines continue to work". Correct?  
> 
> Right. I was a little bit afraid that this might break migration, but I
> gave it a quick check and it still seems to work fine here.
> "info qom-tree" and "info qtree" at the HMP monitor show slightly
> different output, though ... not sure whether that's critical or not?

What looks different? If we still send/expect the same kind of
information, it should not have any impact, I guess.