Re: [PATCH RFC 0/7] Adding core support for wire-MSI bridges

From: Thomas Gleixner
Date: Thu Nov 05 2015 - 07:26:47 EST

On Thu, 5 Nov 2015, Marc Zyngier wrote:
> On 04/11/15 13:34, Thomas Gleixner wrote:
> > Marc,
> >
> > On Fri, 16 Oct 2015, Marc Zyngier wrote:
> >> On 16/10/15 02:55, Jiang Liu wrote:
> >>> There's a working to enable Intel VMD storage device, which
> >>> has the similar requirement. Basically a PCIe hierarchy is hidden
> >>> behind a parent PCIe device, so we need to use the PCIe irqs on parent
> >>> to de-multiple PCIe IRQs from hidden PCIe devices. Seems a chance for
> >>> consolidation here.
> >>
> >> Do you know if there is a 1-1 mapping between the interrupts seen by the
> >> parent device and those seen by the hidden devices? Or is it a case of
> >> having to demultiplex the MSIs? Looks like the former, but I'd like to
> >> be sure.
> >
> > Yes, it's a demultiplexer. No 1:1 mapping.
> Right. This doesn't exactly fit the scheme I have so far (there is a 1:1
> mapping between the wired interrupt and the MSI), but once we are able
> to expose an MSI domain, it could be possible to construct the MSI
> demultiplexer on top. That's a lot of layers! ;-)

Well for the demux case it doesn't make a lot of sense. It's not easy
to describe in a hierarchy. Having that parentless MSI domain for that
VMD case is simple enough.


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