Re: [Xen-devel] x86: adjust handling of interrupts coming in via legacy vectors

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.05.12 at 18:24, Keir Fraser <keir@xxxxxxx> wrote:
> On 14/05/2012 16:56, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> 
>>> Looks sensible, and I suppose good to have for 4.2.
>>> 
>>> Acked-by: Keir Fraser <keir@xxxxxxx>
>> 
>> Please take a look at the v2 I just sent, to accommodate a suggestion
>> from Andrew Cooper.
> 
> I think it's very paranoid, since legacy vectors never get programmed into
> an IOAPIC RTE and should never need EOIing at the local APIC. But you do at
> least printk the case that we see the ISR bit set, and you printk the vector
> number, so really this v2 patch gives us more information about this bogus
> situation than v1 did, so it's a slight improvement overall. So you still
> have my Ack.

It indeed is paranoid (which is why I didn't do so in v1), but Andrew
certainly has a point in saying that something so far unexplainable
going on makes it desirable to cover as many (however remotely)
potential causes as possible. (I still consider double delivery through
IO-APIC and PIC the most likely scenario, despite not having a
reasonably explanation on how the PIC mask bit could get cleared.)

Once we hopefully understand the hole situation, the code here
should likely be reverted to the v1 version (along with removing the
other debugging code).

Jan


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