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

  • To: pgnet.dev@xxxxxxxxx, Xen-users@xxxxxxxxxxxxx
  • From: Sarah Newman <srn@xxxxxxxxx>
  • Date: Fri, 31 Jan 2020 16:45:42 -0800
  • Delivery-date: Sat, 01 Feb 2020 00:46:57 +0000
  • Dkim-filter: OpenDKIM Filter v2.11.0 mail.prgmr.com ABF2D72008A
  • List-id: Xen user discussion <xen-users.lists.xenproject.org>

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

        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
                -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 
                [   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 
 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.


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