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Re: [Xen-users] reboot on booting xen-unstable

On Fri, Jun 8, 2012 at 5:08 AM, Aaron Lebahn <cplusplus328@xxxxxxxxx> wrote:
> Personally, I tried this. I bought a pci serial card and a null modem cable.
> I attached the cable between my card and the usb-pci adapter connected to my
> laptop. I set the grub to:
> multiboot       /boot/xen-4.2.gz placeholder  loglvl=all guest_loglvl=all
> com5=38400,8n1,0xa030,20 console=com5
> and started minicom on the labtop. Noting came up on minicom, and nothing
> came up on the desktop's screen (As should be expected).
> I tested the connection by running minicom on the desktop as well. That
> works fine. My output to dmesg | grep ttyS is:
> [    2.393378] 0000:08:05.0: ttyS4 at I/O 0xa030 (irq = 20) is a ST16650V2
> [    2.449062] 0000:08:05.1: ttyS5 at I/O 0xa020 (irq = 21) is a ST16650V2
> If anyone knows why my serial console isn't working, maybe I can fix it and
> get some useful information to debug this problem.

I used minicom as well in my (successful) attempt. You have to get
minicom to use the right settings, and xen and the kernel don't use
quite the same as minicom does by default so even when minicom can
talk with another minicom it won't necessarily work with xen or the

Since you got your laptop and desktop talking when both use minicom I
expect you have most settings right. What I had to change was: in
minicom, do ctrl-a, then o, then "Serial port setup". Here the default
was to have hardware flow control on. I had to turn it off, and keep
software flow control off too.

Now press e for the bps/etc settings. Mine defaulted at 115200 but I
ended up configuring it (and xen/kernel) at 57600. Your grub line
above would put it at 38400. You also need to have 8n1 configured in
minicom but I think that was the default anyway.

I saved this as the default settings (one or two menus up I think) and
then quit and restarted minicom. I think you may also be able to just
ctrl-a m.

Then, it worked.

One other thing I read about was that you should specify com1
everywhere in your grub line even if you aren't using com1. I was
using com1 there already anyway but you use com5 so that might make a

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