From:   "Tian, Kevin" <kevin.tian@intel.com>
To:     Jason Gunthorpe <jgg@nvidia.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>
CC:     Eric Auger <eric.auger@redhat.com>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Joerg Roedel <joro@8bytes.org>,
        "peter.maydell@linaro.org" <peter.maydell@linaro.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "vivek.gautam@arm.com" <vivek.gautam@arm.com>,
        "kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
        "eric.auger.pro@gmail.com" <eric.auger.pro@gmail.com>,
        "Raj, Ashok" <ashok.raj@intel.com>,
        "maz@kernel.org" <maz@kernel.org>,
        "vsethi@nvidia.com" <vsethi@nvidia.com>,
        "zhangfei.gao@linaro.org" <zhangfei.gao@linaro.org>,
        "will@kernel.org" <will@kernel.org>,
        "alex.williamson@redhat.com" <alex.williamson@redhat.com>,
        "wangxingang5@huawei.com" <wangxingang5@huawei.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "lushenming@huawei.com" <lushenming@huawei.com>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        "robin.murphy@arm.com" <robin.murphy@arm.com>
Subject: RE: [RFC v16 1/9] iommu: Introduce attach/detach_pasid_table API
Thread-Topic: [RFC v16 1/9] iommu: Introduce attach/detach_pasid_table API
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Date:   Thu, 9 Dec 2021 03:59:57 +0000
Message-ID: <BN9PR11MB5276D3B4B181F73A1D62361C8C709@BN9PR11MB5276.namprd11.prod.outlook.com>
References: <20211027104428.1059740-1-eric.auger@redhat.com>
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> From: Tian, Kevin
> Sent: Thursday, December 9, 2021 10:58 AM
>=20
> For ARM it's SMMU's PASID table format. There is no step-2 since PASID
> is already within the address space covered by the user PASID table.
>=20

One correction here. 'no step-2' is definitely wrong here as it means
more than user page table in your plan (e.g. dpdk).

To simplify it what I meant is:

iommufd reports how many 'user page tables' are supported given a device.

ARM always reports only one can be supported, and it must be created in=20
PASID table format. tagged by RID.

Intel reports one in step1 (tagged by RID), and N in step2 (tagged by
RID+PASID). A special flag in attach call allows the user to specify the
additional PASID routing info for a 'user page table'.

Thanks
Kevin