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Re: [libvirt] [PATCH] domain_conf: Include the correct console alias



On Fri, Jun 28, 2013 at 07:34:07PM +0200, Michal Privoznik wrote:
> On 28.06.2013 17:01, Daniel P. Berrange wrote:
> > On Fri, Jun 28, 2013 at 04:45:08PM +0200, Michal Privoznik wrote:
> >> On 28.06.2013 15:55, Daniel P. Berrange wrote:
> >>> On Fri, Jun 28, 2013 at 03:31:17PM +0200, Michal Privoznik wrote:
> >>>> For some crazy backward compatibility, a console can by just an alias to
> >>>> a serial device. This is detected in the XML formating function which
> >>>> takes the values to format from corresponding serial device. Including
> >>>> the device alias. This results in wrong alias being written into the XML
> >>>> definition:
> >>>>
> >>>>     <console type='pty' tty='/dev/pts/5'>
> >>>>       ...
> >>>>       <alias name='serial0'/>
> >>>>     </console>
> >>>>
> >>>> While holding the correct alias still in the memory, it doesn't matter.
> >>>> However, it starts to matter as soon as libvirtd is restarted and the
> >>>> (incorrect) alias is read from status file.
> > 
> > I don't actually see this problem at all.
> > 
> > Starting with a guest containing
> > 
> >     <serial type='pty'>
> >       <target port='0'/>
> >     </serial>
> >     <console type='pty'>
> >       <target type='serial' port='0'/>
> >     </console>
> > 
> > After virsh start, it contains
> > 
> >     <serial type='pty'>
> >       <source path='/dev/pts/7'/>
> >       <target port='0'/>
> >       <alias name='serial0'/>
> >     </serial>
> >     <console type='pty' tty='/dev/pts/7'>
> >       <source path='/dev/pts/7'/>
> >       <target type='serial' port='0'/>
> >       <alias name='serial0'/>
> >     </console>
> > 
> > 
> > The XML in $XDG_RUNTIME_DIR/libvirt/qemu/run/vm1.xml contains
> > exactly the same.
> > 
> > If i now kill libvirtd and restart it, the XML is still
> > reported correctly.
> > 
> > How do you reproduce the bug ?
> 
> The problem is, the internal array (vm->def->consoles) doesn't contain
> just 'consoleX' but 'serialX' too after libvirtd restarts. I've noticed
> this while testing my chardev hotplug patches. If user wants to hotplug
> a console, I need to iterate over vm->def->consoles to find the next
> free X to generate the alias. I am using qemuDomainDeviceAliasIndex for
> that. The function takes alias prefix as one of its arguments. However,
> if the prefix doesn't match, an error is returned. And since the aliases
> vary over libvirtd restarts I think that's the problem. Of course, I can
> workaround it in my patches, but c'mon we want the libvirt source code
> to be hack-less, don't we? :)

Ok, but that's just an internal issue not visible to the user. Your
proposed patches are changing the user visible XML data for the alias
name which is wrong.  So you need to find a way to address it without
causing a change in the user visible XML, which is correct as it is
now.

Daniel
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