Re: [Xen-ia64-devel] vIOSAPIC and IRQs delivery

[Tristan Gingold <Tristan.Gingold@xxxxxxxx>]

I think vIRQs can be divided into two areas:

* interrupt handling in Xen.
* interrupt delivery to domain.

1) Interrupt handling in Xen.
   Currently very minimal: either kept for Xen (IPIs) or reflected to a 
domain.
   We agree IOSAPIC must belong to Xen.  And it should be able to deliver 
interrupts to domains and handle shared IRQs.

2) Interrupt delivery.
Currently this is done using ia64 mechanism (almost full virtualization). 
On xen/x86 this is done using event channel (heavy para-virtualization).

Suppose I update my patch to be able to handle shared IRQs using the in_flight 
mechanism.  Can we agree this is a good first stage and can be submitted as a 
first step too ?

Then, before working on interrupt delivery I'd like to evaluate pros and cons 
of both methods.  This has to be completed and argued.

pros of current mechanism:
* well working for a long time.
* Optimization work.
* few modifications to the kernel.

pros of event channel:
* well working on x86.
* convergence with x86.
* should be faster.

Tristan.

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