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RE: [Xen-devel] IRQ SMP affinity problems in domU with vcpus > 4 on HP ProLiant G6 with dual Xeon 5540 (Nehalem)

>>> "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx> 16.10.09 11:58 >>>
>Keir Fraser wrote:
>> If the EOI is via the local APIC, which I suppose it must be, then a
>> timeout fallback probably is required. This is because priorities are
>> assigned arbitrarily to guest interrupts, and a non-EOIed interrupt
>> blocks any lower-priority interrupts. In particular, some of those
>> could be owned by dom0 for example, and be quite critical to forward
>> progress of the entire system.
>Yeah, exactly same with my concern.  We may need to add the timeout
>mechanism for each interrupt source to avoid that buggy/malicious
>guests hang host through not writing EOI.  

But that's (supposed to be) happening already: If an MSI interrupt is
maskable, the interrupt gets masked and the EOI is sent immediately.
If it's not maskable, a timer gets started to issue the EOI if the guest


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