[Xen-devel] Re: [PATCH] IRQ: manually EOI migrating line interrupts

[Keir Fraser <keir@xxxxxxx>]

On 30/08/2011 15:28, "Andrew Cooper" <andrew.cooper3@xxxxxxxxxx> wrote:

> P.S.
> 
> Because this fix actually works, it means that EOI'ing the IO-APIC is
> keyed only on vector, and not the target CPU.  As a result, having two
> different interrupts in the IO-APIC with the same vector will result in
> problems when trying to EOI one of them.
> 
> I will address this problem as well in my IRQ cleanup, as I cant see any
> checks for it currently.

Isn't this a general issue with per-cpu vector allocations anyway? The usual
irq-completion path of LAPIC EOI -> IO-APIC EOI broadcast will unavoidably
have this issue. Every irq line on every IO-APIC currently programmed with
that vector (regardless of target CPU) will get EOIed/unmasked. Not clear
it's really a problem though! It might cause the odd spurious interrupt
perhaps?

 -- Keir



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