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>]

Keir Fraser wrote:
> On 16/10/2009 09:35, "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx> wrote:
> 
>>>> That maybe a problem if so. If a malicious/buggy guest won't EOI
>>>> the MSI vector, so host may hang due to lack of timeout mechanism?
>>> 
>>> Why does host hang? Only the assigned interrupt will block, and
>>> that's exactly what the guest wants :-)
>> 
>> Hypervisor shouldn't EOI the real vector until guest EOI the
>> corresponding virtual vector , right ?  Not sure.:-)
> 
> 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.  
Xiantao




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