linux-kernel - Re: [PATCH v7 1/8] genirq/msi: Add a new MSI_FLAG_IRQ

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Message-ID: <alpine.DEB.2.11.1604221739070.3941@nanos>
Date:	Fri, 22 Apr 2016 17:39:53 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Eric Auger <eric.auger@...aro.org>
cc:	Robin Murphy <robin.murphy@....com>, eric.auger@...com,
	alex.williamson@...hat.com, will.deacon@....com, joro@...tes.org,
	jason@...edaemon.net, marc.zyngier@....com,
	christoffer.dall@...aro.org, linux-arm-kernel@...ts.infradead.org,
	patches@...aro.org, linux-kernel@...r.kernel.org,
	Bharat.Bhushan@...escale.com, pranav.sawargaonkar@...il.com,
	p.fedin@...sung.com, iommu@...ts.linux-foundation.org,
	Jean-Philippe.Brucker@....com, julien.grall@....com
Subject: Re: [PATCH v7 1/8] genirq/msi: Add a new MSI_FLAG_IRQ_REMAPPING
 flag

On Fri, 22 Apr 2016, Eric Auger wrote:
> Robin,
> On 04/22/2016 01:02 PM, Robin Murphy wrote:
> > Hi Eric,
> > 
> > On 19/04/16 18:13, Eric Auger wrote:
> >> Let's introduce a new msi_domain_info flag value, MSI_FLAG_IRQ_REMAPPING
> >> meant to tell the domain supports IRQ REMAPPING, also known as Interrupt
> >> Translation Service. On Intel HW this IRQ remapping capability is
> >> abstracted on IOMMU side while on ARM it is abstracted on MSI controller
> >> side. This flag will be used to know whether the MSI passthrough is
> >> safe.
> > 
> > Perhaps a nitpick, but given the earlier confusion about what the IOMMU
> > flag actually meant this prompts me to wonder if it's worth adjusting
> > the general terminology before we propagate it further. What I think we
> > actually care about is that one thing or the other "provides MSI
> > isolation" rather than "supports MSI remapping", since the latter is all
> > to easy to misinterpret the way we did in the SMMU drivers.
> 
> The only concern I have is https://lkml.org/lkml/2016/4/18/283 attempts
> to define a PCI bus flag dubbed PCI_BUS_FLAGS_MSI_REMAP combining the
> iommu & msi layer info. In that sense x86 people may not be keen of
> having different terminaologies. Anyway I will follow the consensus, if any.

Yes, please keep that consistent. It makes 'grep' much more conveniant.

Thanks,

	tglx