[Differential] D7185: Add virtio-console support to bhyve

[Jakub Klama]

> Wiadomość napisana przez Paul Vixie <paul at redbarn.org> w dniu 11.07.2016, o godz. 19:27:
> 
> fwiw, bhyve's existing console support is working fine for me. i use rtty (from ports). my configuration looks like this:
> 
> [mm1.redbarn:amd64] ls -l /usr/local/rtty/dev
> total 3
> lrwxr-xr-x  1 root  wheel  11 May 18  2014 family@ -> /dev/nmdm2A
> lrwxr-xr-x  1 root  wheel  11 May 17  2014 guests@ -> /dev/nmdm0A
> lrwxr-xr-x  1 root  wheel  11 Nov 16  2014 pbx@ -> /dev/nmdm5A
> lrwxr-xr-x  1 root  wheel  11 Jun  1  2014 sleipnir@ -> /dev/nmdm3A
> lrwxr-xr-x  1 root  wheel  11 May 18  2014 util@ -> /dev/nmdm1A
> lrwxr-xr-x  1 root  wheel  11 May  1  2015 yeti-dns@ -> /dev/nmdm7A
> 
> the bhyve processes are using the corresponding "B" devices. rtty keeps logs:
> 
> [mm1.redbarn:amd64] ls -l /usr/local/rtty/log/
> total 164401
> -rw-r-----  1 root  wheel    2132344 Jul 10 07:18 family
> -rw-r-----  1 root  wheel    1176529 Jul 10 03:58 guests
> -rw-r-----  1 root  wheel    1964961 Jul 11 06:23 pbx
> -rw-r-----  1 root  wheel  133664527 Jul 11 17:25 sleipnir
> -rw-r-----  1 root  wheel   17943116 Jul 11 17:06 util
> -rw-r-----  1 root  wheel   11042436 Jul 11 17:11 yeti-dns
> 
> so i can find out why something crashed even if i wasn't watching at the time.
> 
> so, i'm having trouble understanding the need for virtio-console to be able to open a host-side unix-domain socket in the file system?
> 

The purpose of virtio-console is to create arbitrary bidirectional, host-to-guest communication
channels that bypass guest's network stack (don't require working networking in the guest).
But even for using it as the system console, it's a bit better than emulated serial port, because
the protocol supports passing console resize events from host to guest.

Jakub