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Date:   Thu, 15 Jul 2021 09:48:13 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     "Tian, Kevin" <kevin.tian@intel.com>
Cc:     Shenming Lu <lushenming@huawei.com>,
        "Alex Williamson (alex.williamson@redhat.com)" 
        <alex.williamson@redhat.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        David Gibson <david@gibson.dropbear.id.au>,
        Jason Wang <jasowang@redhat.com>,
        "parav@mellanox.com" <parav@mellanox.com>,
        "Enrico Weigelt, metux IT consult" <lkml@metux.net>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Joerg Roedel <joro@8bytes.org>,
        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>,
        Kirti Wankhede <kwankhede@nvidia.com>,
        Robin Murphy <robin.murphy@arm.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        David Woodhouse <dwmw2@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        "wanghaibin.wang@huawei.com" <wanghaibin.wang@huawei.com>
Subject: Re: [RFC v2] /dev/iommu uAPI proposal
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On Thu, Jul 15, 2021 at 06:49:54AM +0000, Tian, Kevin wrote:

> No. You are right on this case. I don't think there is a way to 
> differentiate one mdev from the other if they come from the
> same parent and attached by the same guest process. In this
> case the fault could be reported on either mdev (e.g. the first
> matching one) to get it fixed in the guest.

If the IOMMU can't distinguish the two mdevs they are not isolated
and would have to share a group. Since group sharing is not supported
today this seems like a non-issue

Jason