linux-kernel - Re: [PATCH v5 04/14] driver core: platform: Add driver dma ownership management

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Message-ID: <20220214131853.GY4160@nvidia.com>
Date:   Mon, 14 Feb 2022 09:18:53 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Dan Williams <dan.j.williams@...el.com>, rafael@...nel.org,
        Diana Craciun <diana.craciun@....nxp.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Chaitanya Kulkarni <kch@...dia.com>,
        Stuart Yoder <stuyoder@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Li Yang <leoyang.li@....com>,
        Dmitry Osipenko <digetx@...il.com>,
        iommu@...ts.linux-foundation.org, linux-pci@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 04/14] driver core: platform: Add driver dma ownership
 management

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.

Jason