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Date:   Fri, 16 Apr 2021 11:34:51 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Auger Eric <eric.auger@redhat.com>
Cc:     "Liu, Yi L" <yi.l.liu@intel.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        "Tian, Kevin" <kevin.tian@intel.com>,
        Jacob Pan <jacob.jun.pan@linux.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>,
        "cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
        Tejun Heo <tj@kernel.org>, Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Jean-Philippe Brucker <jean-philippe@linaro.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Jonathan Corbet <corbet@lwn.net>,
        "Raj, Ashok" <ashok.raj@intel.com>, "Wu, Hao" <hao.wu@intel.com>,
        "Jiang, Dave" <dave.jiang@intel.com>
Subject: Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and
 allocation APIs
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On Fri, Apr 16, 2021 at 04:26:19PM +0200, Auger Eric wrote:

> This was largely done during several confs including plumber, KVM forum,
> for several years. Also API docs were shared on the ML. I don't remember
> any voice was raised at those moments.

I don't think anyone objects to the high level ideas, but
implementation does matter. I don't think anyone presented "hey we
will tunnel an uAPI through VFIO to the IOMMU subsystem" - did they?

Look at the fairly simple IMS situation, for example. This was
presented at plumbers too, and the slides were great - but the
implementation was too hacky. It required a major rework of the x86
interrupt handling before it was OK.

Jason