Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <ccba785d-9000-09f0-7ca8-b21834924ced@linux.intel.com>
Date:   Thu, 28 Jul 2022 14:27:30 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.11.0
Cc:     baolu.lu@linux.intel.com, Joerg Roedel <joro@8bytes.org>,
        Christoph Hellwig <hch@infradead.org>,
        Kevin Tian <kevin.tian@intel.com>,
        Ashok Raj <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Vinod Koul <vkoul@kernel.org>,
        Eric Auger <eric.auger@redhat.com>,
        Liu Yi L <yi.l.liu@intel.com>,
        Jacob jun Pan <jacob.jun.pan@intel.com>,
        Zhangfei Gao <zhangfei.gao@linaro.org>,
        Zhu Tony <tony.zhu@intel.com>, iommu@lists.linux.dev,
        linux-kernel@vger.kernel.org,
        Jean-Philippe Brucker <jean-philippe@linaro.org>
Content-Language: en-US
To:     Jason Gunthorpe <jgg@nvidia.com>
References: <20220705050710.2887204-1-baolu.lu@linux.intel.com>
 <20220705050710.2887204-5-baolu.lu@linux.intel.com>
 <20220723141118.GD79279@nvidia.com>
 <686b137f-232a-2a78-beb0-e4373bd20959@linux.intel.com>
 <20220725144005.GE3747@nvidia.com>
 <6da27a6b-b580-4ba4-24c8-ebdfb2d9345d@linux.intel.com>
 <20220726135722.GC4438@nvidia.com>
 <cf370e4a-9391-4dd3-1e0a-3c7ea70d9ed2@linux.intel.com>
From:   Baolu Lu <baolu.lu@linux.intel.com>
Subject: Re: [PATCH v10 04/12] iommu: Add attach/detach_dev_pasid iommu
 interface
In-Reply-To: <cf370e4a-9391-4dd3-1e0a-3c7ea70d9ed2@linux.intel.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

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