Re: [Qemu-devel] [PATCH v1] hw/s390x: Allow to configure the consoles with the "-serial" parameter

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 04/25/2018 07:21 AM, 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, even for virtual
> consoles like spapr-vty on the pseries machine. So let's support this
> option on s390x, too. This way we can easily enable the serial console
> here again with "-nodefaults", for example:
> 
> qemu-system-s390x -no-shutdown -nographic -nodefaults -serial mon:stdio
> 
> ... which is way shorter than typing:
> 
> qemu-system-s390x -no-shutdown -nographic -nodefaults \
>   -chardev stdio,id=c1,mux=on -device sclpconsole,chardev=c1 \
>   -mon chardev=c1
> 
> The -serial parameter can also be used if you only want to see the QEMU
> monitor on stdio without using -nodefaults, but not the console output.
> That's something that is pretty impossible with the current code today:
> 
> qemu-system-s390x -no-shutdown -nographic -serial none
> 
> While we're at it, this patch also maps the second -serial option to the
> "sclplmconsole", so that there is now an easy way to configure this second
> console on s390x, too, for example:
> 
> qemu-system-s390x -no-shutdown -nographic -serial null -serial mon:stdio
> 
> Additionally, the new code is also smaller than the old one and we have
> less s390x-specific code in vl.c :-)
> 
> I've also checked that migration still works as expected by migrating
> a guest with console output back and forth between a qemu-system-s390x
> that has this patch and an instance without this patch.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>

Very nice. I tested some combinations (only limited test) and everything looks
good. 

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>