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    SubjectRe: [PATCH 4/5] iommu: Support mm PASID 1:n with sva domains
    On Tue, Aug 08, 2023 at 03:49:43PM +0800, Tina Zhang wrote:
    > Each mm bound to devices gets a PASID and corresponding sva domains
    > allocated in iommu_sva_bind_device(), which are referenced by iommu_mm
    > field of the mm. The PASID is released in __mmdrop(), while a sva domain
    > is released when on one is using it (the reference count is decremented
    > in iommu_sva_unbind_device()).
    >
    > Since the required info of PASID and sva domains is kept in struct
    > iommu_mm_data of a mm, use mm->iommu_mm field instead of the old pasid
    > field in mm struct. The sva domain list is protected by iommu_sva_lock.
    >
    > Besides, this patch removes mm_pasid_init(), as with the introduced
    > iommu_mm structure, initializing mm pasid in mm_init() is unnecessary.
    >
    > Signed-off-by: Tina Zhang <tina.zhang@intel.com>
    > ---
    > drivers/iommu/iommu-sva.c | 38 +++++++++++++++++++++++++-------------
    > include/linux/iommu.h | 10 +++-------
    > kernel/fork.c | 1 -
    > 3 files changed, 28 insertions(+), 21 deletions(-)
    >
    > diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
    > index 0a4a1ed40814..35366f51ad27 100644
    > --- a/drivers/iommu/iommu-sva.c
    > +++ b/drivers/iommu/iommu-sva.c
    > @@ -15,6 +15,7 @@ static DEFINE_IDA(iommu_global_pasid_ida);
    > /* Allocate a PASID for the mm within range (inclusive) */
    > static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
    > {
    > + struct iommu_mm_data *iommu_mm = NULL;
    > int ret = 0;
    >
    > if (min == IOMMU_PASID_INVALID ||
    > @@ -33,11 +34,22 @@ static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t ma
    > goto out;
    > }
    >
    > + iommu_mm = kzalloc(sizeof(struct iommu_mm_data), GFP_KERNEL);
    > + if (!iommu_mm) {
    > + ret = -ENOMEM;
    > + goto out;
    > + }
    > +
    > ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, GFP_KERNEL);
    > - if (ret < 0)
    > + if (ret < 0) {
    > + kfree(iommu_mm);
    > goto out;
    > + }
    > +
    > + iommu_mm->pasid = ret;
    > + mm->iommu_mm = iommu_mm;
    > + INIT_LIST_HEAD(&mm->iommu_mm->sva_domains);
    >
    > - mm->pasid = ret;
    > ret = 0;
    > out:
    > mutex_unlock(&iommu_sva_lock);
    > @@ -82,16 +94,12 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm

    Lets please rework this function into two parts

    The first should be 'iommu_sva_alloc_domain()'

    It should do the list searching and user management. The usual
    'iommu_domain_free()' should be modified to clean it up.

    Then you have the 'alloc global/enqcmd pasid' function

    Then bind is just callling alloc sva domain, alloc global pasid,
    set_dev_pasid in a sequence.

    It will make this much more understandable what all the parts are
    supposed to be doing.

    Jason

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