linux-kernel - Re: [PATCH v8 01/11] iommu: Add DMA ownership management interfaces

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Message-ID: <d8bbe591-b6c3-d44a-7a7d-3187e8377e4f@arm.com>
Date:   Tue, 8 Mar 2022 13:37:05 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>
Cc:     kvm@...r.kernel.org, rafael@...nel.org,
        David Airlie <airlied@...ux.ie>, linux-pci@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>,
        Diana Craciun <diana.craciun@....nxp.com>,
        Dmitry Osipenko <digetx@...il.com>,
        Will Deacon <will@...nel.org>,
        Stuart Yoder <stuyoder@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Chaitanya Kulkarni <kch@...dia.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Cornelia Huck <cohuck@...hat.com>,
        linux-kernel@...r.kernel.org, Li Yang <leoyang.li@....com>,
        iommu@...ts.linux-foundation.org,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH v8 01/11] iommu: Add DMA ownership management interfaces

On 2022-03-08 05:44, Lu Baolu wrote:
> Multiple devices may be placed in the same IOMMU group because they
> cannot be isolated from each other. These devices must either be
> entirely under kernel control or userspace control, never a mixture.
> 
> This adds dma ownership management in iommu core and exposes several
> interfaces for the device drivers and the device userspace assignment
> framework (i.e. VFIO), so that any conflict between user and kernel
> controlled dma could be detected at the beginning.
> 
> The device driver oriented interfaces are,
> 
> 	int iommu_device_use_default_domain(struct device *dev);
> 	void iommu_device_unuse_default_domain(struct device *dev);
> 
> By calling iommu_device_use_default_domain(), the device driver tells
> the iommu layer that the device dma is handled through the kernel DMA
> APIs. The iommu layer will manage the IOVA and use the default domain
> for DMA address translation.
> 
> The device user-space assignment framework oriented interfaces are,
> 
> 	int iommu_group_claim_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 DMA owner
> claiming interface returns failure.

Reviewed-by: Robin Murphy <robin.murphy@....com>

> Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Kevin Tian <kevin.tian@...el.com>
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>