linux-kernel - Re: [RFC V1 RESEND 2/6] PCI/MSI: Dynamic allocation of MSI-X vectors by group

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Message-ID: <alpine.DEB.2.21.1908110919310.7324@nanos.tec.linutronix.de>
Date:   Sun, 11 Aug 2019 09:20:29 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Marc Zyngier <marc.zyngier@....com>
cc:     Megha Dey <megha.dey@...el.com>, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        ashok.raj@...el.com, jacob.jun.pan@...ux.intel.com
Subject: Re: [RFC V1 RESEND 2/6] PCI/MSI: Dynamic allocation of MSI-X vectors
 by group

On Wed, 7 Aug 2019, Marc Zyngier wrote:
> On 07/08/2019 14:56, Thomas Gleixner wrote:
> > On Tue, 6 Aug 2019, Megha Dey wrote:
> >> On Sat, 2019-06-29 at 09:59 +0200, Thomas Gleixner wrote:
> >>> On Fri, 21 Jun 2019, Megha Dey wrote:
> >>
> >> Totally agreed. The request to add a dynamic MSI-X infrastructure came
> >> from some driver teams internally and currently they do not have
> >> bandwidth to come up with relevant test cases. <sigh>
> > 
> > Hahahaha.
> > 
> >> But we hope that this patch set could serve as a precursor to the
> >> interrupt message store (IMS) patch set, and we can use this patch set
> >> as the baseline for the IMS patches.
> > 
> > If IMS needs the same functionality, then we need to think about it
> > slightly differently because IMS is not necessarily tied to PCI.
> >  
> > IMS has some similarity to the ARM GIC ITS stuff IIRC, which already
> > provides these things outside of PCI. Marc?
> 
> Indeed. We have MSI-like functionality almost everywhere, and make heavy
> use of the generic MSI framework. Platform-MSI is probably the most
> generic example we have (it's the Far West transposed to MSIs).
> 
> > We probably need some generic infrastructure for this so PCI and everything
> > else can use it.
> 
> Indeed. Overall, I'd like the concept of MSI on whatever bus to have one
> single behaviour across the board, as long as it makes sense for that
> bus (nobody needs another PCI MultiMSI, for example).

Right.

@Intel: Is there documentation and perhaps early code for that IMS muck to
	look at?

Thanks,

	tglx