[libvirt-users] pty pairing host - guest

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 ? This is what I've tried: dumpxml returns <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/ttyS0. so I opened screen/cat/echo on both sides but could not exchange messages ------ 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. My sole requirement is to have a tty pair in host and guest that can be used to communicate with each other. I am using qemu-kvm. Thank You.

On Thu, Mar 19, 2015 at 01:29:37PM +0530, Neel Basu wrote:
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
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 :|
participants (2)
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Daniel P. Berrange
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Neel Basu