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

[Sarah Newman <srn@xxxxxxxxx>]

On 1/31/20 5:39 PM, PGNet Dev wrote:
> On 1/31/20 4:45 PM, Sarah Newman wrote:
> > 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.
> i was just poking at that myself.
>
> @ https://xenbits.xen.org/docs/4.13-testing/misc/xen-command-line.html#com1
>
> it says
>
> "The accepted name keywords for name=value pairs are:
>      ...
>      io-base - accepts integer which specified IO base port for UART registers
>      ...
> "
>
> i.e., hyphenated. then, in the next comment,
>
>         "
>         The following are examples of correct specifications:
>         
>         com1=115200,8n1,0x3f8,4
>         com1=115200,8n1,0x3f8,4,reg_width=4,reg_shift=2
>         com1=baud=115200,parity=n,stop_bits=1,io_base=0x3f8,reg_width=4
>         "
>
> note, *all* underscores :-/
>
> If I use underscores,
>
>         com1=baud=115200,data_bits=8,parity=n,stop_bits=1,io_base=0x03e8,irq=3
>
> the /dev/ttyS2 device *is* defined and probeable on boot.
>
> OTOH, with hyphens, there's no /dev created.
>
> Haven't yet found any *errors* abt it :-S
>
> Need to take a look at the code myself & monkey with logging to understand 
> what's right.
>
> > I looked up the ttyS2 port and irq using
> >
> > $ cat /sys/class/tty/ttyS2/device/resources
> > state = active
> here,
>
>         cat /sys/class/tty/ttyS2/device/resources
>                 state = active
>                 io 0x3e8-0x3ef
>                 irq 3
>                 dma disabled
>
> > serial --unit=2 --speed=115200
> > terminal_input serial console
> > terminal_output serial console
> I mod'd  /etc/default/grub to
>
>         GRUB_TERMINAL_INPUT="serial console "
>         GRUB_TERMINAL_OUTPUT="serial console"
>         GRUB_SERIAL_COMMAND="serial --unit=2 --speed=115200"
>
> and, switched to the 'shorthand',
>
>         GRUB_CMDLINE_XEN="com1=115200,8n1,0x03e8,3 console=com1,vga ..."
>
> and updated the initrd.
>
> verifying,
>
>         grep serial /boot/grub2/grub.cfg
>                 serial --unit=2 --speed=115200
>                 terminal_input serial console
>                 terminal_output serial console
>
> and
>
>         grep com /boot/grub2/xen-4.13.0_04-lp151.688.cfg
>                 ... com1=115200,8n1,0x03e8,3 console=com1,vga
>
> after reboot, there's unfortunately NO assigned UART
>
>         setserial -g /dev/ttyS* | grep 03e8
>                 /dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 3
>
> and the /dev can't be written,
>
>         /bin/stty -F /dev/ttyS2 115200 raw -echo
>                 /bin/stty: /dev/ttyS2: Input/output error
>
> ok, confused.
That sounds like Xen claiming the serial port.

Given you want Xen and Linux to share a serial port, shouldn't you be using the 
virtual serial port hvc0 within Linux when booted under xen?


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