linux-kernel - Re: [PATCH v5 01/14] iommu: Add dma ownership management interfaces

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Date:   Thu, 6 Jan 2022 11:18:24 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...dia.com>,
        Bjorn Helgaas <helgaas@...nel.org>
Cc:     baolu.lu@...ux.intel.com, Christoph Hellwig <hch@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        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 01/14] iommu: Add dma ownership management interfaces

On 1/5/22 3:23 AM, Jason Gunthorpe wrote:
>>>> The vfio oriented interfaces are,
>>>>
>>>> 	int iommu_group_set_dma_owner(struct iommu_group *group,
>>>> 				      void *owner);
>>>> 	void iommu_group_release_dma_owner(struct iommu_group *group);
>>>> 	bool iommu_group_dma_owner_claimed(struct iommu_group *group);
>>>>
>>>> The device userspace assignment must be disallowed if the set dma owner
>>>> interface returns failure.
>> Can you connect this back to the "never a mixture" from the beginning?
>> If all you cared about was prevent an IOMMU group from containing
>> devices with a mixture of kernel drivers and userspace drivers, I
>> assume you could do that without iommu_device_use_dma_api().  So is
>> this a way to*allow*  a mixture under certain restricted conditions?
> It is not about user/kernel, it is about arbitrating the shared
> group->domain against multiple different requests to set it to
> something else.
> 
> Lu, Given that the word 'user' was deleted from the API entirely it
> makes sense to reword these commit messages to focus less on user vs
> kernel and more on ownership of the domain pointer.

Sure. Will do it.

Best regards,
baolu