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

    On Tue, 15 Mar 2022 11:33:22 -0300, Jason Gunthorpe <jgg@nvidia.com> wrote:

    > 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.
    >
    > 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..
    >
    Agreed.
    It might need some surgery for dmar_domain and device_domain_info, which
    already has a simple device list. I am trying to leverage the existing data
    struct, let me take a closer look.

    > > + if (entry) {
    > > + pinfo = entry;
    > > + } else {
    > > + pinfo = kzalloc(sizeof(*pinfo), GFP_ATOMIC);
    > > + if (!pinfo)
    > > + return -ENOMEM;
    > > + pinfo->pasid = pasid;
    > > + /* Store the new PASID info in the per domain array */
    > > + ret = xa_err(__xa_store(&dmar_domain->pasids, pasid,
    > > pinfo,
    > > + GFP_ATOMIC));
    > > + if (ret)
    > > + goto xa_store_err;
    > > + }
    > > + /* Store PASID in per device-domain array, this is for
    > > tracking devTLB */
    > > + ret = xa_err(xa_store(&info->pasids, pasid, pinfo,
    > > GFP_ATOMIC));
    > > + if (ret)
    > > + goto xa_store_err;
    > > +
    > > + atomic_inc(&pinfo->users);
    > > + xa_unlock(&dmar_domain->pasids);
    > > +
    > > + return 0;
    > > +
    > > +xa_store_err:
    > > + xa_unlock(&dmar_domain->pasids);
    > > + spin_lock_irqsave(&iommu->lock, flags);
    > > + intel_pasid_tear_down_entry(iommu, dev, pasid, false);
    > > + spin_unlock_irqrestore(&iommu->lock, flags);
    > > +
    > > + if (!atomic_read(&pinfo->users)) {
    > > + __xa_erase(&dmar_domain->pasids, pasid);
    >
    > This isn't locked right
    >
    good catch! need to move under xa_unlock.

    Thanks,

    Jacob

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