Re: [Xen-devel] [PATCH 0/6] xen: Support continuations from tasklets

[Jan Beulich <jbeulich@xxxxxxxx>]

On 06.12.2019 11:14, Andrew Cooper wrote:
> On 06/12/2019 09:58, Jan Beulich wrote:
>> On 05.12.2019 23:30, Andrew Cooper wrote:
>>> From testing this series, I have re-confirmed the previous reported
>>> observation that:
>>>
>>>   # while :; do xen-hptool smt-enable; xen-hptool smt-disable; done
>>>
>>> in dom0 eventually causes the serial console to cease working (wedge midway
>>> through printing a line).
>>>
>>> There are sporadic "Broke affinity for IRQ26, new: ffff" messages, but the
>>> serial always seems to break shortly after the first "Broke affinity for
>>> IRQ30, new: ffff".  Both IRQs are non-descript PCI-MSI/-X interrupts bound 
>>> to
>>> dom0.
>> And neither IRQ30 not IRQ26 are the serial ones? And serial does
>> use an IRQ (i.e. isn't running in polling mode)? I'll see if I
>> can repro (and then maybe be able to debug).
> 
> Serial uses IRQ0 and never has affinity changes as it is always bound to
> CPU0.

IRQ0? DYM IRQ3 or IRQ4? (In any event the important part is for it
to be in the ISA range, rather than the PCI one.)

> Given our recent fun with the PEOI stack, that was going to be my next
> port of call.  However everything else in the system looks to be working
> fine, including the disks and network, suggesting that we aren't losing
> other interrupts.

The high priority vector we use for serial makes the PEOI stack
unrelated afaict, as mentioned in the discussion there as well.

Jan

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