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    Subject[PATCH 4/5] iommu: Support mm PASID 1:n with sva domains
    Date
    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

    mutex_lock(&iommu_sva_lock);
    /* Search for an existing domain. */
    - domain = iommu_get_domain_for_dev_pasid(dev, mm_get_pasid(mm),
    - IOMMU_DOMAIN_SVA);
    - if (IS_ERR(domain)) {
    - ret = PTR_ERR(domain);
    - goto out_unlock;
    - }
    -
    - if (domain) {
    - domain->users++;
    - goto out;
    + list_for_each_entry(domain, &mm->iommu_mm->sva_domains, next) {
    + ret = iommu_attach_device_pasid(domain, dev, mm_get_pasid(mm));
    + if (!ret) {
    + domain->users++;
    + goto out;
    + }
    }

    /* Allocate a new domain and set it on device pasid. */
    @@ -105,6 +113,8 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm
    if (ret)
    goto out_free_domain;
    domain->users = 1;
    + list_add(&domain->next, &mm->iommu_mm->sva_domains);
    +
    out:
    mutex_unlock(&iommu_sva_lock);
    handle->dev = dev;
    @@ -137,8 +147,9 @@ void iommu_sva_unbind_device(struct iommu_sva *handle)
    struct device *dev = handle->dev;

    mutex_lock(&iommu_sva_lock);
    + iommu_detach_device_pasid(domain, dev, pasid);
    if (--domain->users == 0) {
    - iommu_detach_device_pasid(domain, dev, pasid);
    + list_del(&domain->next);
    iommu_domain_free(domain);
    }
    mutex_unlock(&iommu_sva_lock);
    @@ -218,4 +229,5 @@ void mm_pasid_drop(struct mm_struct *mm)
    return;

    ida_free(&iommu_global_pasid_ida, mm_get_pasid(mm));
    + kfree(mm->iommu_mm);
    }
    diff --git a/include/linux/iommu.h b/include/linux/iommu.h
    index 435d1c1afd23..6a87df6d8637 100644
    --- a/include/linux/iommu.h
    +++ b/include/linux/iommu.h
    @@ -109,6 +109,7 @@ struct iommu_domain {
    struct { /* IOMMU_DOMAIN_SVA */
    struct mm_struct *mm;
    int users;
    + struct list_head next;
    };
    };
    };
    @@ -1177,17 +1178,13 @@ static inline bool tegra_dev_iommu_get_stream_id(struct device *dev, u32 *stream
    }

    #ifdef CONFIG_IOMMU_SVA
    -static inline void mm_pasid_init(struct mm_struct *mm)
    -{
    - mm->pasid = IOMMU_PASID_INVALID;
    -}
    static inline bool mm_valid_pasid(struct mm_struct *mm)
    {
    - return mm->pasid != IOMMU_PASID_INVALID;
    + return mm->iommu_mm ? true : false;
    }
    static inline u32 mm_get_pasid(struct mm_struct *mm)
    {
    - return mm->pasid;
    + return mm->iommu_mm ? mm->iommu_mm->pasid : IOMMU_PASID_INVALID;
    }
    void mm_pasid_drop(struct mm_struct *mm);
    struct iommu_sva *iommu_sva_bind_device(struct device *dev,
    @@ -1209,7 +1206,6 @@ static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
    {
    return IOMMU_PASID_INVALID;
    }
    -static inline void mm_pasid_init(struct mm_struct *mm) {}
    static inline bool mm_valid_pasid(struct mm_struct *mm) { return false; }
    static inline u32 mm_get_pasid(struct mm_struct *mm)
    {
    diff --git a/kernel/fork.c b/kernel/fork.c
    index d2e12b6d2b18..f06392dd1ca8 100644
    --- a/kernel/fork.c
    +++ b/kernel/fork.c
    @@ -1274,7 +1274,6 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
    mm_init_cpumask(mm);
    mm_init_aio(mm);
    mm_init_owner(mm, p);
    - mm_pasid_init(mm);
    RCU_INIT_POINTER(mm->exe_file, NULL);
    mmu_notifier_subscriptions_init(mm);
    init_tlb_flush_pending(mm);
    --
    2.17.1
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