linux-kernel - Re: [PATCH v10 04/12] iommu: Add attach/detach_dev

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Message-ID: <YurGexaP/Q+N02dT@nvidia.com>
Date:   Wed, 3 Aug 2022 16:03:23 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        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>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Zhangfei Gao <zhangfei.gao@...aro.org>,
        Zhu Tony <tony.zhu@...el.com>, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Subject: Re: [PATCH v10 04/12] iommu: Add attach/detach_dev_pasid iommu
 interface

On Wed, Aug 03, 2022 at 09:07:35PM +0800, Baolu Lu wrote:
> +/**
> + * iommu_device_claim_pasid_owner() - Set ownership of a pasid on device
> + * @dev: the device.
> + * @pasid: the pasid of the device.
> + * @owner: caller specified pointer. Used for exclusive ownership.
> + *
> + * Return 0 if it is allowed, otherwise an error.
> + */
> +int iommu_device_claim_pasid_owner(struct device *dev, ioasid_t pasid, void
> *owner)

I don't see a use case for a special "pasid owner"

PASID is no different from normal DMA. If the calling driver already
has the proper ownership of the device/group then it is fine for that
driver to use any kind of IOMMU attachment, RID, PASID, whatever. It
doesn't matter *how* the attachment is made.

Remember the series that got dropped about converting all the drivers
to the new ownership scheme? That is how it should work - owernship
and domain attach are two different operations and do not get mixed
confusingly together. (and are you going to repost that series? It
would be great to get it done)

Jason