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

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 20/07/2012 20:10, "Christopher S. Aker" <caker@xxxxxxxxxxxx> 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?

Somehow dom0 disabled the serial-line interrupt during boot. Possibly it
appeared as a PnP device in some BIOS table and dom0 decided to disable it
because it doesn't think it is being used. Xen would usually stop this
happening via programming of the IO-APIC/XT-PIC but perhaps there is some
other method of disabling it on this mainboard, which Xen doesn't catch.

 -- Keir

> -Chris
> 
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