linux-kernel - RE: [RFC v2] /dev/iommu uAPI proposal

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Date:   Tue, 13 Jul 2021 23:24:45 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     Alex Williamson <alex.williamson@...hat.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        David Gibson <david@...son.dropbear.id.au>,
        Jason Wang <jasowang@...hat.com>,
        "parav@...lanox.com" <parav@...lanox.com>,
        "Enrico Weigelt, metux IT consult" <lkml@...ux.net>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Shenming Lu <lushenming@...wei.com>,
        Joerg Roedel <joro@...tes.org>,
        Eric Auger <eric.auger@...hat.com>,
        "Jonathan Corbet" <corbet@....net>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>, "Wu, Hao" <hao.wu@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "Kirti Wankhede" <kwankhede@...dia.com>,
        Robin Murphy <robin.murphy@....com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "David Woodhouse" <dwmw2@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Lu Baolu" <baolu.lu@...ux.intel.com>
Subject: RE: [RFC v2] /dev/iommu uAPI proposal

> From: Jason Gunthorpe <jgg@...dia.com>
> Sent: Wednesday, July 14, 2021 7:23 AM
> 
> On Tue, Jul 13, 2021 at 11:20:12PM +0000, Tian, Kevin wrote:
> > > From: Jason Gunthorpe <jgg@...dia.com>
> > > Sent: Wednesday, July 14, 2021 7:03 AM
> > >
> > > On Tue, Jul 13, 2021 at 10:48:38PM +0000, Tian, Kevin wrote:
> > >
> > > > We can still bind to the parent with cookie, but with
> > > > iommu_register_ sw_device() IOMMU fd knows that this binding
> doesn't
> > > > need to establish any security context via IOMMU API.
> > >
> > > AFAIK there is no reason to involve the parent PCI or other device in
> > > SW mode. The iommufd doesn't need to be aware of anything there.
> > >
> >
> > Yes. but does it makes sense to have an unified model in IOMMU fd
> > which always have a [struct device, cookie] with flags to indicate whether
> > the binding/attaching should be specially handled for sw mdev? Or
> > are you suggesting that lacking of struct device is actually the indicator
> > for such trick?
> 
> I think you've veered into such micro implementation details that it
> is better to wait and see how things look.
> 
> The important point here is that whatever physical device is under a
> SW mdev does not need to be passed to the iommufd because there is
> nothing it can do with that information.
> 

Make sense