Re: [Xen-devel] [PATCH]: Really disable pirq's

[Chris Lalancette <clalance@xxxxxxxxxx>]

Jiang, Yunhong wrote:
> Not sure if the change is a bit over-kill, since enable_pirq is has void
> return type, while startup_pirq is "int" return type, with possibility
> to fail.

Thanks for looking!

This is true, startup_pirq() *could* fail; but if you notice in the code, it
doesn't actually have anything but a "return 0", so it doesn't report errors
currently anyway.

> 
> For example, in following situation, the startup_pirq may fail : 1) when
> startup_pirq again, fail to get free port, 2) if another domain try to
> bind the pirq with BIND_PIRQ_WILL_SHARE cleared (like to probing, will
> it happen?) between the shutdown_pirq/startup_pirq sequence.

Yes, you are right, this can happen if another domain is probing.  However, I'm
not sure that it is any different from when you are calling ->startup() for the
first time; you will just fail to get the event channel.  Without introducing
another event channel op (which seems like a LOT of overkill), I'm not aware of
another way of asking the HV to mask out that IRQ on the IOAPIC.

Chris Lalancette

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