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Re: [Xen-devel] Xen 4 serial hangs during boot

On 20/07/12 20:10, Christopher S. Aker wrote:
> On 7/20/12 2:05 PM, Andrew Cooper wrote:
>> Alternatively, use `xl debug-keys`
> Interesting.  'xl debug-keys h' got me ~1448 bytes onto the serial 
> console, except it is old buffered output from exactly where it left off 
> during boot. 1448 bytes is about the size of 'h' output from another 
> working box.  The same thing happened with 'm'.  Xen is flushing an 
> equal amount of characters from the buffer as generated by debug-key 
> command output.
> I can continue to poke the buffer until I see output from things I've 
> issued, however it still refuses to respond to serial input 
> (control-aaa) nor can I get dom0 to echo chars.  It's currently running 
> a * dump which has been going now for over an hour, currently on vcpu 
> 435628.  I won't be doing that again.
> Any lightblubs going off?

Not especially.  It sounds like the serial ring buffer filled up and
never got drained.

How easy is this to reproduce for you? In the past, I have had success
debugging Xen like this with an outb(0x3f8, <ascii char>) in certain
locations.  Perhaps the serial_rx interrupt handler, or failing that,
do_irq checking for vector 0xf0.  That should allow you to see whether
Xen is actually receiving interrupts when you try to send characters.

> -Chris

Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com

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