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Re: [Xen-devel] console driver - How domain0 processes console messages ?

  • To: Anthony Liguori <anthony@xxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxxx
  • From: Richard <judicator3@xxxxxxxxx>
  • Date: Sun, 20 Feb 2005 22:04:26 -0500
  • Delivery-date: Mon, 21 Feb 2005 03:05:52 +0000
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On Wed, 16 Feb 2005 19:26:24 -0600, Anthony Liguori
<anthony@xxxxxxxxxxxxx> wrote:
> The easiest thing to do though would probably be to launch vm-create
> (part of vm-tools) with the -i option (interactive) and just step
> through it with gdb.
> The message flow isn't terribly obvious just by looking at the code
> however it should be quite understandable in gdb.
> Let me know when you get to implementing support for virtual devices (if
> you do).  I've got all sorts of xcs/xu debugging stuff that I'm going to
> eventually clean-up and submit.  They're pretty granular for most of the
> important messages (dumping out every field in all the messages).
> Good luck :-)

Thanks Anthony.
Your debugging tools will be very helpful. 
I actually got the console driver to output correctly on mini-os.
However, I can only ouput a limited amount of data. After some time my
communication ring gets filled up and I cannot send anything. I've
tracked down my problem. The reason is because my mini-os does not
handle interrupts (or events) very well.

The backend driver in Domain0 sends an event to mini-os each time it
processes a message from the communication ring. Mini-os should
receive that event and update its communication ring pointers.
However, the entry.S file in mini-os is pretty outdated and mini-os
does not behave correctly after receiving its 1st interrupt. I've been
looking at XenoLinux's entry.S file and trying to adapt the one in
mini-os but I don't quite undestand what is going on in there and I
have not been successful so far.


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