Re: Multiple MSI

[Grant Grundler <grundler@parisc-linux.org>]

On Mon, Jul 07, 2008 at 10:39:19AM -0600, Matthew Wilcox wrote:
...
> > If the Local-APICs are able to redirect interrupts, then multiple CPUs
> > can process the interrupts.
> 
> That's not the only way it can work.  If you have an APIC per root bus,
> you can target that with the write.  The APIC could then map the
> interrupt request to the appropriate CPU.  In this scenario, programming
> affinity would be twiddling some bits in the APIC and not need to write
> to the device's MSI register at all.

Ok...but that still means it's got only one target (either one CPU
or a group of CPUs).

> What I've implemented for x86-64 can target any mask of CPUs that are
> in the same interrupt domain.  My machine only has one interrupt domain,
> so I can target the MSI to any subset of the CPUs.  They all move
> together, so you can't target a different subset of CPUs for different
> MSIs on the same device.

*nod* - that's what I meant.

thanks,
grant