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Date:   Fri, 17 Sep 2021 07:05:43 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     "Tian, Kevin" <kevin.tian@intel.com>
Cc:     Jason Gunthorpe <jgg@ziepe.ca>,
        Kirti Wankhede <kwankhede@nvidia.com>,
        Christoph Hellwig <hch@lst.de>,
        Alex Williamson <alex.williamson@redhat.com>,
        Diana Craciun <diana.craciun@oss.nxp.com>,
        Cornelia Huck <cohuck@redhat.com>,
        Eric Auger <eric.auger@redhat.com>,
        "Xu, Terrence" <terrence.xu@intel.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH 11/14] vfio: clean up the check for mediated device in
 vfio_iommu_type1
Message-ID: <20210917050543.GA22003@lst.de>
References: <20210913071606.2966-1-hch@lst.de> <20210913071606.2966-12-hch@lst.de> <c4ef0d8a-39f4-4834-f8f2-beffd2f2f8ae@nvidia.com> <20210916221854.GT3544071@ziepe.ca> <BN9PR11MB54333BE60F997D3A9183EDD38CDD9@BN9PR11MB5433.namprd11.prod.outlook.com>
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On Fri, Sep 17, 2021 at 04:49:41AM +0000, Tian, Kevin wrote:
> > You just use the new style mdev API and directly call
> > vfio_register_group_dev and it will pick up the
> > parent->dev->iommu_group naturally like everything else using physical
> > iommu groups.
> > 
> 
> For above usage (wrap pdev into mdev), isn't the right way to directly add 
> vendor vfio-pci driver since vfio-pci-core has been split out now? It's not 
> necessary to fake a mdev just for adding some mediation in the r/w path...

Exactly.

> Another type of IOMMU-backed mdev is with pasid support. But for this
> case we discussed earlier that it doesn't have group and will follow the
> new /dev/iommu proposal instead.

Indeed.