Re: PCI Express

[Colin Ngam <cngam@sgi.com>]

Jesse Barnes wrote:

> On Tuesday, March 08, 2005 4:13 pm, Colin Ngam wrote:
> > That's what I will find out before deciding to use it.  It is not used for
> > IPIs on our platform, probably for very good reasons.
>
> Yep, because IPIs generated from the local block to a distant processor won't
> work otherwise (afaik).
>
> > If we can and the
> > address is the same than it is a no brainer.
> >
> > > targetted there should also work.  The problem for us is if a processor
> > > tries to IPI a processor on a different node with the processor interrupt
> > > block, which I don't think MSIs will try to do.
> >
> > Perhaps you can elaborate.  I am not sure what you are trying to say here.
>
> The SHub manual is a little vague here, but my understanding is that in order
> to send remote IPIs we need to use the SHub, whereas local IPIs (i.e.
> processor to itself or to the other CPU on the same FSB) will work fine.
>
> An MSI should behave like a processor sending an IPI to itself since its
> address can be targeted at the processor's interrupt block and set to
> generate a local interrupt.  Is that right, Tom & Grant?
>
> If this won't work for us, no biggie, we just have to abstract things a little
> more.  We could make the MSI into a platform specific cookie that we can
> store a SHub/PIC/TIO address in and other platforms can use to target the
> processor interrupt block.  Hopefully we won't have to do that though, since
> it would require a few more changes.

May be the way we go.  Needs more perusal of the MSI code.

Thanks.

colin

>
>
> Jesse
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