Getting no output on /dev/hvcNN On Thu, Mar 19, 2015 at 3:15 PM, Daniel P. Berrange <berrange@redhat.com> wrote:

On Thu, Mar 19, 2015 at 01:29:37PM +0530, Neel Basu wrote:

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HI!,

I am using virt-manager GUI. There I can add a `Console Device` through Add Hardware. I can add a virtio pty WITHOUT restarting the VM. also I get a pty allocated to host machine say `/dev/pty/M`

My expectation is this `host:/dev/pty/M` is connected with a `guest:/dev/ttyN`. so If I open minicom or screen and write to `host:/dev/pty/M` it will be propagated to 'guest:/dev/ttyN'. Is my expectation correct ?

If it is correct how will I know what is the guest tty allocated against this host pty ?

No, that's not how it works. The <console> devices are exposed to the guest as /dev/hvcNN devices. Starting with NN==0

as per the dumpxml output

<console type='pty' tty='/dev/pts/1'> <source path='/dev/pts/1'/> <target type='serial' port='0'/> <alias name='serial0'/> </console> I expected host:/dev/pts/1 is paired with guest:/dev/hvc0 So I tried to communicate with minicom,echo,cat with these two but I saw no output. what I echo on /dev/pts/1 doesn't pass to /dev/hvc0 or vice verse.

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Similar to console device I can add a Serial device but that requires a reboot of the guest VM. However I tried that though I prefer to do it without a guest restart.

<serial type='pty'> <source path='/dev/pts/1'/> <target port='0'/> <alias name='serial0'/> </serial>

here also I expected host:/dev/pts/1 is paired with /dev/ttyS0 but couldn't communicate.

The serial port device supported is a 1990 era ISA bus serial port so there's no hotplug for that. Only the paravirt consoles can be hotplugged.

Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|