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

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 23/07/2012 15:13, "Konrad Rzeszutek Wilk" <konrad.wilk@xxxxxxxxxx> wrote:

> On Fri, Jul 20, 2012 at 08:59:29PM +0100, Keir Fraser wrote:
>> On 20/07/2012 20:44, "Christopher S. Aker" <caker@xxxxxxxxxxxx> wrote:
>> 
>>> On 7/20/12 3:31 PM, Keir Fraser wrote:
>>>> 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.
>>> 
>>> Hmm -- except dom0 hasn't even booted yet at the time the serial stops
>>> working.  Xen is 30-60 seconds away from booting dom0 given the RAM
>>> scrub still has to happen.
>> 
>> Then it is Xen doing something to kill the serial interrupt. ;-) I haven't
>> seen anything like this reported before. Not sure what to suggest really...
>> Gather debug output from interrupt-related debug keys (via the xl debug-keys
>> interface) I suppose. I think that would be 'i' and 'z' keys. That plus Xen
>> and dom0 boot logs... something might become apparent.
> 
> What about using the serial line without the interrupt?
> Meaning com1=115200,8n1,0x3f8,0
> 
> That ought to make the code go into polling and ignore the interrupt line
> right?

Yes, that should work. It does waste some CPU time runnign the poll handler
continually, even when the serial line is idle. And of course serial debug
key inputs will still not work.

 -- Keir

>> 
>>  -- Keir
>> 
>>> -Chris
>> 
>> 
>> 
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