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    SubjectRe: [PATCH v2 3/8] iommu/vt-d: Implement device_pasid domain attach ops
    Hi Kevin,

    On Wed, 16 Mar 2022 07:41:34 +0000, "Tian, Kevin" <kevin.tian@intel.com>
    wrote:

    > > From: Jason Gunthorpe <jgg@nvidia.com>
    > > Sent: Tuesday, March 15, 2022 10:33 PM
    > >
    > > On Mon, Mar 14, 2022 at 10:07:07PM -0700, Jacob Pan wrote:
    > > > + /*
    > > > + * Each domain could have multiple devices attached with
    > > > shared or
    > > per
    > > > + * device PASIDs. At the domain level, we keep track of
    > > > unique PASIDs
    > > and
    > > > + * device user count.
    > > > + * E.g. If a domain has two devices attached, device A has
    > > > PASID 0, 1;
    > > > + * device B has PASID 0, 2. Then the domain would have PASID
    > > > 0, 1, 2.
    > > > + */
    > >
    > > A 2d array of xarray's seems like a poor data structure for this task.
    >
    Perhaps i mis-presented here, I am not using 2D array. It is an 1D xarray
    for domain PASIDs only. Then I use the existing device list in each domain,
    adding another xa to track per-device-domain PASIDs.
    > besides that it also doesn't work when we support per-device PASID
    > allocation in the future. In that case merging device PASIDs together is
    > conceptually wrong.
    >
    Sorry, could you elaborate? If we do per-dev PASID allocation, we could use
    the ioasid_set for each pdev, right?

    > >
    > > AFACIT this wants to store a list of (device, pasid) tuples, so a
    > > simple linked list, 1d xarray vector or a red black tree seems more
    > > appropriate..
    > >
    >
    > this tuple can well serve per-device PASID. 😊
    >
    I commented on the other email, but a simple list of tuples could have
    duplicated devices since each dev could attach multiple PASIDs, right?
    Should we still do two level then?

    > Thanks
    > Kevin


    Thanks,

    Jacob

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