Re: [Xen-devel] [PATCH 0/5] Add MSI support to XEN

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 31/3/08 15:25, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:

>> So, if you leave the driver as it is (triggering the software LSC
>> interrupt), do APIC EOI in Xen before executing the interrupt
>> handler in
>> dom0, and do not mask the MSI at all, then you no longer hang?
> 
> I usuually do experiement in linux kernel, and it no longer hang.

Well, I'd be okay with an initial implementation which does not allow Xen to
mask MSIs. But still I think it will be cleaner and more extensible to have
Xen program the MSI registers anyway. This will hide details like interrupt
vector, APIC destination mode, etc. from the MSI-capable guest, and also
will make it easier to support things like changing interrupt affinity on
the fly (since it will not be necessary to get dom0 involved in that).

Once you have Xen able to write the MSI registers, I suppose it is not much
extra work to implement some kind of interrupt mitigation scheme involving
mask/enable bits of the MSI configuration register.

 -- Keir



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