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    SubjectRE: [PATCH v2 3/8] iommu/sva: Support reservation of global SVA PASIDs
    Date
    > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
    > Sent: Tuesday, March 28, 2023 7:22 AM
    >
    > +/**
    > + * @brief
    > + * Reserve a PASID from the SVA global number space.
    > + *
    > + * @param min starting range, inclusive
    > + * @param max ending range, inclusive
    > + * @return The reserved PASID on success or IOMMU_PASID_INVALID on
    > failure.
    > + */
    > +ioasid_t iommu_sva_reserve_pasid(ioasid_t min, ioasid_t max)
    > +{
    > + int ret;
    > +
    > + if (!pasid_valid(min) || !pasid_valid(max) ||
    > + min == 0 || max < min)
    > + return IOMMU_PASID_INVALID;
    > +
    > + ret = ida_alloc_range(&iommu_global_pasid_ida, min, max,
    > GFP_KERNEL);
    > + if (ret < 0)
    > + return IOMMU_PASID_INVALID;
    > +
    > + return ret;
    > +}
    > +EXPORT_SYMBOL_GPL(iommu_sva_reserve_pasid);
    > +

    Look at this function. There is no single word about sva except
    in the function name.

    sva is just one user of global pasids.

    when a driver supports sva it has to always use global pasids even
    for non-sva usages like dma pasid.

    but this doesn't mean that we should build the API around sva.

    it's really about global pasids.

    let's just call it clearly as iommu_alloc_global_pasid(min, max).

    Then we can define a wrapper iommu_reserve_global_pasid(pasid)
    as iommu_alloc_global_pasid(pasid, pasid).

    for PASID#0 driver calls iommu_reserve_global_pasid(0).

    for dma pasid driver calls iommu_alloc_global_pasid() to get a random
    one instead of reserving pasid#1.

    this would be future proof when the same driver starts to allocate
    more pasids for other usages e..g siov.

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