RE: [PATCH] Allow xen to share device with domain (RE: [PATCH]RE:[Xen-ia64-devel] xencons interrupt problem)

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

>From: Alex Williamson [mailto:alex.williamson@xxxxxx]
>Sent: 2006年7月7日 6:14
>
>On Tue, 2006-07-04 at 09:49 +0800, Tian, Kevin wrote:
>> Hi, Alex,
>>      Could you try attached patch to see whether progressing a step
>> for you? It's made on top of last patch, to address a bug that
>> VEC_XEN_ALIAS is only meaningful when enable bit is on. This bug
>> may result guest to think shared irq line edge-triggered and thus no
>> EOI request is issued which may stuck the subsequent instances. :-)
>
>Hi Kevin,
>
>   Good catch with this patch, but it still hangs.  Besides having xen
>call end() in __do_IRQ(), I can also prevent the hang by booting with
>sync_console.  If I INIT the system when it's hung, the only CPU that's
>not in the idle loop is sitting in do_console_io(), maybe into
>guest_console_write() (which appears to be getting inlined).  I'm
>wondering if the problem is actually Xen spinning there waiting for tx
>space and preventing the guest from calling end().  I added a loop
>counter for debug, but I haven't been able to make it pop out yet.
>Thanks,
>
>       Alex
>

That's the possible cause. Actually I seldom considered serial driver 
itself before:-). Does it spin tx buffer in irq handler or somewhere else 
with irq disabled? Which event may cause xen into infinite spin? If spin 
can exit, xenlinux can be resumed and then end() should be triggered... 

Thanks,
Kevin

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