[illumos-Developer] Available MSI(-x) interrupt limit.

[Garrett D'Amore]

Yes.    The limit comes from the fact that ill behaved devices/drivers could easily consume all the interrupts on a system, preventing other devices from attaching.  There was a recent rearchitecture of the interrupt code specifically for MSI-X that offers far more interrupt vectors to devices, in exchange for the device registering a callback indicating a willingness to return interrupts back to the system when they become scarce.

There's also a legacy override somewhere that you can use for specific devices, but it isn't documented.  I don't remember the name of the override, but it can grow the set up to 8.

  -- Garrett D'Amore

On Jun 7, 2011, at 5:49 PM, "Alexey Zaytsev" <alexey.zaytsev at gmail.com> wrote:

> Hey.
> 
> Any ideas, what's the reason to have the 2 msi per device limit?
> It's been there from the start of the history.
> 
> https://github.com/illumos/illumos-gate/blob/master/usr/src/uts/common/os/ddi_intr_impl.c#L296
> https://github.com/illumos/illumos-gate/blob/master/usr/src/uts/common/os/ddi_intr_impl.c#L40
> https://github.com/illumos/illumos-gate/blob/master/usr/src/uts/common/sys/ddi_intr_impl.h#L146
> 
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