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Date:   Wed, 2 Jun 2021 14:24:24 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     "Enrico Weigelt, metux IT consult" <lkml@metux.net>
Cc:     "Tian, Kevin" <kevin.tian@intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        David Woodhouse <dwmw2@infradead.org>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "Alex Williamson (alex.williamson@redhat.com)" 
        <alex.williamson@redhat.com>, Jason Wang <jasowang@redhat.com>,
        Eric Auger <eric.auger@redhat.com>,
        Jonathan Corbet <corbet@lwn.net>,
        "Raj, Ashok" <ashok.raj@intel.com>,
        "Liu, Yi L" <yi.l.liu@intel.com>, "Wu, Hao" <hao.wu@intel.com>,
        "Jiang, Dave" <dave.jiang@intel.com>,
        Jacob Pan <jacob.jun.pan@linux.intel.com>,
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        David Gibson <david@gibson.dropbear.id.au>,
        Kirti Wankhede <kwankhede@nvidia.com>,
        Robin Murphy <robin.murphy@arm.com>
Subject: Re: [RFC] /dev/ioasid uAPI proposal
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On Wed, Jun 02, 2021 at 10:56:48AM +0200, Enrico Weigelt, metux IT consult wrote:

> If I understand this correctly, /dev/ioasid is a kind of "common supplier"
> to other APIs / devices. Why can't the fd be acquired by the
> consumer APIs (eg. kvm, vfio, etc) ?

/dev/ioasid would be similar to /dev/vfio, and everything already
deals with exposing /dev/vfio and /dev/vfio/N together

I don't see it as a problem, just more work.

Having FDs spawn other FDs is pretty ugly, it defeats the "everything
is a file" model of UNIX.

Jason