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Date:   Tue, 30 Mar 2021 10:27:40 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     "Tian, Kevin" <kevin.tian@intel.com>
Cc:     Jacob Pan <jacob.jun.pan@linux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        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>,
        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>
Subject: Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and
 allocation APIs
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On Tue, Mar 30, 2021 at 04:14:58AM +0000, Tian, Kevin wrote:

> One correction. The mdev should still construct the list of allowed PASID's as
> you said (by listening to IOASID_BIND/UNBIND event), in addition to the ioasid 
> set maintained per VM (updated when a PASID is allocated/freed). The per-VM
> set is required for inter-VM isolation (verified when a pgtable is bound to the 
> mdev/PASID), while the mdev's own list is necessary for intra-VM isolation when 
> multiple mdevs are assigned to the same VM (verified before loading a PASID 
> to the mdev). This series just handles the general part i.e. per-VM ioasid set and 
> leaves the mdev's own list to be managed by specific mdev driver which listens
> to various IOASID events).

This is better, but I don't understand why we need such a convoluted
design.

Get rid of the ioasid set.

Each driver has its own list of allowed ioasids.

Register a ioasid in the driver's list by passing the fd and ioasid #

No listening to events. A simple understandable security model.

Look - it took you three emails to even correctly explain the security
model you are striving for here, it is *obviously* too complicated for
anyone to understand or successfully implement. simplify smiplify
simplify.

Jason