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

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Date:	Thu, 05 Nov 2015 12:22:08 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Jason Cooper <jason@...edaemon.net>,
	Ma Jun <majun258@...wei.com>,
	linux-arm-kernel@...ts.infradead.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 0/7] Adding core support for wire-MSI bridges

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! ;-)

>> Sure, will do when I repost this (probably in a few weeks), and assuming
>> this fits the bill for Thomas and the MBIGEN folks.
> 
> It doesn't look that bad and the resulting mbigen stuff is way less
> horrible than it was before. So I agree this is a possible solution to
> the problem.

Cool. I'll revisit that after the merge window.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...
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