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

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Message-ID: <ccba785d-9000-09f0-7ca8-b21834924ced@linux.intel.com>
Date:   Thu, 28 Jul 2022 14:27:30 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     baolu.lu@...ux.intel.com, 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 2022/7/28 10:44, Baolu Lu wrote:
>>
>> If the fabric routes PASID properly then groups are not an issue - all
>> agree on this?
> 
> I still think the singleton group is required, but it's not related to
> the PCI fabric routing discussed here.
> 
> We have a single array for PASIDs in the iommu group. All devices
> sitting in the group should share a single PASID namespace. However both
> the translation structures for IOMMU hardware or the device drivers can
> only adapt to per-device PASID namespace. Hence, it's reasonable to
> require the singleton group.

Further, conceptually, we cannot support pasid attach/detach on multi-
device groups. If multiple devices cannot be isolated, it is difficult
to ensure that their pasid spaces are isolated from each other.
Therefore, it is wrong to attach a domain to the pasid of a device. All
devices in the group must share a domain.

Best regards,
baolu