[libvirt] [PATCH v2 1/2] conf: add debugcon chardev guest interface

[Andrea Bolognani]

On Mon, 2019-02-11 at 08:14 +0000, Nikolay Shirokovskiy wrote:
> On 08.02.2019 17:34, Andrea Bolognani wrote:
> > Even with that fixed, while your code prevents a <console> element
> > associated to the isa-debugcon to be automatically created, it
> > doesn't prevent something like
> > 
> >   <console type='pty'/>
> >   <serial type='file'>
> >     <source path='...'/>
> >     <target type='isa-serial'>
> >       <model name='isa-debugcon'/>
> >     </target>
> >   </serial>
> > 
> > to result in the same problematic configuration, while the user
> > clearly wanted to have both a regular serial console *and* the
> > isa-debugcon.
> 
> Yeah I noticed that too but I though this is like case of usb-serial
> for example. We do not add missing console in that case but allow
> existing console to be alias of usb-serial.

Hm, that looks like a bug. I think we should be consistent about
this: either the aliasing between <serial/> and <console/> works
both ways, or it should not happen at all IMHO.

> Can usb-serial actually be console?

No idea :)

> > > +    <serial type='pipe'>
> > > +      <source path='/tmp/debugcon'/>
> > > +      <target type='isa-serial' port='0'>
> > > +        <model name='isa-debugcon'/>
> > > +      </target>
> > > +      <address type='isa' iobase='0x402'/>
> > > +    </serial>
> > 
> > So IIUC iobase=0x402 is the de-facto standard for isa-debugcon,
> > right?
> > 
> > Assuming that's indeed the case, I would expect libvirt to fill in
> > that value automatically unless the user has provided an iobase
> > explicitly themselves.
> 
> I wonder then why qemu uses a different value - 0xe9?

If that's the default value for isa-debugcon.iobase as far as QEMU
is concerned, then we should use that value in libvirt too. But I
thought you said 0x402 was the default?

-- 
Andrea Bolognani / Red Hat / Virtualization