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Date:   Mon, 14 Feb 2022 14:37:15 +0100
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Jason Gunthorpe <jgg@nvidia.com>
Cc:     Lu Baolu <baolu.lu@linux.intel.com>,
        Joerg Roedel <joro@8bytes.org>,
        Alex Williamson <alex.williamson@redhat.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Christoph Hellwig <hch@infradead.org>,
        Kevin Tian <kevin.tian@intel.com>,
        Ashok Raj <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Dan Williams <dan.j.williams@intel.com>, rafael@kernel.org,
        Diana Craciun <diana.craciun@oss.nxp.com>,
        Cornelia Huck <cohuck@redhat.com>,
        Eric Auger <eric.auger@redhat.com>,
        Liu Yi L <yi.l.liu@intel.com>,
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        Jonathan Hunter <jonathanh@nvidia.com>,
        Li Yang <leoyang.li@nxp.com>,
        Dmitry Osipenko <digetx@gmail.com>,
        iommu@lists.linux-foundation.org, linux-pci@vger.kernel.org,
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Subject: Re: [PATCH v5 04/14] driver core: platform: Add driver dma ownership
 management
Message-ID: <YgpbC1u6YFN4GefB@kroah.com>
References: <20220104015644.2294354-1-baolu.lu@linux.intel.com>
 <20220104015644.2294354-5-baolu.lu@linux.intel.com>
 <YgooFjSWLTSapuIs@kroah.com>
 <20220214131853.GY4160@nvidia.com>
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On Mon, Feb 14, 2022 at 09:18:53AM -0400, Jason Gunthorpe wrote:
> On Mon, Feb 14, 2022 at 10:59:50AM +0100, Greg Kroah-Hartman wrote:
> 
> > > +	if (ret && !drv->no_kernel_api_dma)
> > > +		iommu_device_unuse_dma_api(dev);
> > 
> > So you are now going to call this for every platform driver _unless_
> > they set this flag?
> 
> Yes, it is necessary because VFIO supports platform devices as well
> and needs to ensure security. Conflicting kernel driver attachements
> must be blocked, just like for PCI.

A platform device shouldn't be using VFIO, but ugh, oh well, that ship
has sailed :(

And stop it with the "security" mess, do not give people a false sense
of it here please.

thanks,

greg k-h