Re: [Xen-users] serial console to Dom0 -- connection, but only 'garbage' (� , 'question mark') output. config wrong?

[Sarah Newman <srn@xxxxxxxxx>]

On 1/31/20 4:26 PM, PGNet Dev wrote:
> i'm running Xen 14.3 Dom0 (hvm) on a linux 5.5.0-24.g3f183bf-default kernel
>
> i'm setting up serial console.
>
> BIOS is setup for serial redirection over COM1 at port 0x03e8, irq 3
>
> on boot, verifying
>
>         lsdev | grep serial
>                 serial 03e8-03ef f080-f087
>
>         setserial -g /dev/ttyS* | grep -i 03e8
>                 /dev/ttyS2, UART: 16550A, Port: 0x03e8, IRQ: 3
>
>         setserial /dev/ttyS2 -a
>                 /dev/ttyS2, Line 2, UART: 16550A, Port: 0x03e8, IRQ: 3
>                 Baud_base: 115200, close_delay: 50, divisor: 0
>                 closing_wait: 3000
>                 Flags: spd_normal skip_test
>
>         grep ttyS2 /etc/securetty
>                 ttyS2
>
>         cat /etc/udev/rules.d/60-serial.rules
>                 KERNEL=="ttyS2", RUN+="/bin/stty -F /dev/ttyS2 115200 raw -echo"
>
>         stty -F /dev/ttyS2
>                 speed 115200 baud; line = 0;
>                 min = 1; time = 0;
>                 -brkint -icrnl -imaxbel
>                 -opost
>                 -isig -icanon -echo
>
>         grep -i 03e8 /proc/tty/driver/serial
>                 2: uart:16550A port:000003E8 irq:3 tx:469 rx:13 CTS|CD|RI
>
>         dmesg | grep -i tty | grep -vi line
>                 [    1.862201] printk: console [tty0] enabled
>                 [    3.780961] 00:05: ttyS2 at I/O 0x3e8 (irq = 3, base_baud = 
> 115200) is a 16550A
>                 [    3.803169] 0000:00:16.3: ttyS4 at I/O 0xf080 (irq = 17, 
> base_baud = 115200) is a 16550A
>                 [   19.662043] systemd[1]: Created slice 
> system-serial\x2dgetty.slice.
>                 [   19.675518] systemd[1]: Created slice system-getty.slice.
>                 [   49.846481] systemd[1]: Started Serial Getty on hvc0.
>                 [   49.847963] systemd[1]: Started Getty on tty1.
>
> grub2's config'd with
>
>         GRUB_TERMINAL_INPUT="console serial"
>         GRUB_TERMINAL_OUTPUT="console serial"
>         GRUB_SERIAL_COMMAND="serial --port=0x03e8 --speed=115200"
>         GRUB_CMDLINE_LINUX_XEN_REPLACE="xencons=xvc console=tty0 console=hvc0 
> ..."
>         
> GRUB_CMDLINE_XEN=""com1=baud=115200,data-bits=8,parity=n,stop-bits=1,io_base=0x03e8,irq=3
>  console=com1,vga ..."
>
> desktop <-> server are connected via null-modem serial cable
>
> on exec at server,
>
>         echo -e "testtesttest" > /dev/ttyS2
>
> on my desktop, where
>
>         stty -F /dev/ttyS0
>                 speed 115200 baud; line = 0;
>                 min = 1; time = 5;
>                 ignbrk -brkint -icrnl -imaxbel
>                 -opost -onlcr
>                 -isig -icanon -iexten -echo -echoe -echok -echoctl -echoke
>
> either at
>
>         cat  /dev/ttyS0
>
> or in 'minicom', with matched comm params, there's only 'garbage' output -- 
> specifically one
>
>         � (question mark)
>
> for each echo exec.  not the expected "testtesttest" ...
>
> what's missing/wrong in that^ config?
I have a server using ttyS2 for Xen.

I looked up the ttyS2 port and irq using

$ cat /sys/class/tty/ttyS2/device/resources
state = active
io 0x3e8-0x3ef
irq 10
dma disabled

I think grub can handle serial port 2 natively so you don't need to explicitly 
specify it. IE if you have this in your grub.cfg, it should work:

serial --unit=2 --speed=115200
terminal_input serial console
terminal_output serial console

Then referring to https://wiki.xenproject.org/wiki/Xen_Serial_Console, for Xen 
I used:

com1=115200,8n1,0x3e8,10 console=com1

But in newer versions of Xen the syntax you're using should be supported. Looking at the source files docs/misc/xen-command-line.pandoc and 
xen/drivers/char/ns16550.c, I think there's a problem with hyphens versus underscores.
Try changing io_base to io-base in your command line.

--Sarah



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