[Xen-users] Correction: Serial Console Not Connecting to Dom0 on Ubuntu Server 12 Running Xen 4.1.3

[John McDermott CIV <john.mcdermott@xxxxxxxxxxxx>]

> Xen-users,
> 
> I have what I think is a bug in the serial console interaction of Xen and 
> Ubuntu. Essentially, the serial console appears to work just fine until it is 
> passed off to dom 0 from Xen. Then it stops communicating with dom0, but 
> still communicates with Xen, if I use the control-A escape sequence. Google 
> will not show me anything related to this.
> 
> I have local RS-232 serial console working correctly, when the host is Fedora 
> instead of Ubuntu, so I know that the client side is just fine. I have tried 
> 2 different clients, Linux Mint and Mac OS X, with the identical problematic 
> results.
> 
> Serial connection to bare metal Ubuntu 12 works just fine.
> 
> The serial console shows all of the GRUB and Xen boot messages but then seems 
> to disconnect from dom 0. Serial I/O to the firmware works fine; I can stop 
> the boot and change the BIOS. Serial I/O to GRUB works fine, I can work with 
> GRUB. However when booting from Xen into dom 0, the serial I/O seems to be 
> only going to the hypervisor.
> 
> I have tried with and without an hvc0.cfg file in /etc/init but it makes no 
> difference.
> 
> The xm dmesg does not give me much help:
> 
> ----
> root@xenpro3:~# xm dmesg | grep serial
> (XEN) ******* that all output is synchronously delivered on the serial line.
> ----
> 
> Serial console output server side, failure at last line (mountall)
> ----
> Loading the saved-state of the serial devices... 
> /dev/ttyS1 at 0x02f8 (irq = 3) is a 16550A
> * Stopping System V initialisation compatibility                        [ OK ]
> * Starting System V runlevel compatibility                              [ OK ]
> * Starting save kernel messages                                         [ OK ]
> * Starting KVM                                                          [ OK ]
> * Starting automatic crash report generation                            [ OK ]
> * Starting ACPI daemon                                                  [ OK ]
> * Starting regular background program processing daemon                 [ OK ]
> * Starting deferred execution scheduler                                 [ OK ]
> * Starting CPU interrupts balancing daemon                              [ OK ]
> * Starting crash report submission daemon                               [ OK ]
> * Starting Block the mounting event for NFS filesytems until statd is ru[ OK ]
> * Stopping Block the mounting event for NFS filesytems until statd is ru[ OK ]
> * Starting libvirt daemon                                               [ OK ]
> * Exporting directories for NFS kernel daemon...                        [ OK 
> ] 
> * Stopping save kernel messages                                         [ OK ]
> * Starting configure network device security                            [ OK ]
> * Starting configure network device                                     [ OK ]
> * Starting NFS kernel daemon                                            [ OK 
> ] 
> SSL tunnels disabled, see /etc/default/stunnel4
> * Starting Block the mounting event for NFS filesytems until statd is ru[ OK ]
> * Stopping Block the mounting event for NFS filesytems until statd is ru[ OK ]
> [   18.782960] XENBUS: Unable to read cpu state
> [   18.787858] XENBUS: Unable to read cpu state
> [   18.792665] XENBUS: Unable to read cpu state
> [   18.797492] XENBUS: Unable to read cpu state
> * Starting Xen daemons                                                  [ OK 
> ] 
> * Stopping System V runlevel compatibility                              [ OK ]
> mountall: Disconnected from Plymouth
> 
> ----
> 
> If I press Control-A 3 times, I get
> ----
> [   18.797492] XENBUS: Unable to read cpu state
> * Starting Xen daemons                                                  [ OK 
> ] 
> * Stopping System V runlevel compatibility                              [ OK ]
> mountall: Disconnected from Plymouth
> (XEN) *** Serial input -> Xen (type 'CTRL-a' three times to switch input to 
> DOM0)
> ----
> 
> /etc/default/grub 
> ----
> 
> # If you change this file, run 'update-grub' afterwards to update
> # /boot/grub/grub.cfg.
> # For full documentation of the options in this file, see:
> #   info -f grub -n 'Simple configuration'
> 
> GRUB_TERMINAL=serial
> GRUB_SERIAL_COMMAND="serial --port=0x3f8 --unit=0 --speed=115200 --word=8 
> --parity=no --stop=1"
> 
> GRUB_DEFAULT="Xen"
> #GRUB_HIDDEN_TIMEOUT=0
> GRUB_HIDDEN_TIMEOUT_QUIET=true
> GRUB_TIMEOUT=32
> GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
> GRUB_CMDLINE_XEN="loglvl=all com1=115200,8n1 console=com1,vga 
> console_to_ring, sync_console"
> GRUB_CMDLINE_LINUX_DEFAULT=""
> GRUB_CMDLINE_LINUX="console=hvc0 earlyprintk=xen"
> 
> 
> # Uncomment to enable BadRAM filtering, modify to suit your needs
> # This works with Linux (no patch required) and with any kernel that obtains
> # the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
> #GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"
> 
> # Uncomment to disable graphical terminal (grub-pc only)
> #GRUB_TERMINAL=console
> 
> # The resolution used on graphical terminal
> # note that you can use only modes which your graphic card supports via VBE
> # you can see them in real GRUB with the command `vbeinfo'
> #GRUB_GFXMODE=640x480
> ----

Correction, wrong hypervisor. Same problem with the binary from Canonical, so 
its not likely caused by the hypervisor per se:

root@xenpro3:~# xm info
host                   : xenpro3
release                : 3.2.0-30-generic
version                : #48-Ubuntu SMP Fri Aug 24 16:52:48 UTC 2012
machine                : x86_64
nr_cpus                : 4
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 3392
hw_caps                : 
bfebfbff:28100800:00000000:00003f40:13bae3ff:00000000:00000001:00000000
virt_caps              : hvm hvm_directio
total_memory           : 16108
free_memory            : 1427
free_cpus              : 0
xen_major              : 4
xen_minor              : 1
xen_extra              : .2
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 
hvm-3.0-x86_32p hvm-3.0-x86_64 
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : unavailable
xen_commandline        : placeholder loglvl=all com1=115200,8n1 
console=com1,vga console_to_ring, sync_console
cc_compiler            : gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) 
cc_compile_by          : stefan.bader
cc_compile_domain      : canonical.com
cc_compile_date        : Sat Jul 21 09:01:19 UTC 2012
xend_config_format     : 4

----
What is the formal meaning of the one-line program
#include "/dev/tty"

J.P. McDermott                  building 12
Code 5542                       john.mcdermott@xxxxxxxxxxxx
Naval Research Laboratory       voice: +1 202.404.8301
Washington, DC 20375, US        fax:   +1 202.404.7942











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