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    SubjectRe: [PATCH RFC v2 03/11] iommu/sva: Add iommu_domain type for SVA
    From
    On 2022/3/30 5:38, Jacob Pan wrote:
    >> +static struct iommu_domain *
    >> +iommu_sva_alloc_domain(struct device *dev, struct mm_struct *mm)
    >> +{
    >> + struct bus_type *bus = dev->bus;
    >> + struct iommu_sva_cookie *cookie;
    >> + struct iommu_domain *domain;
    >> + void *curr;
    >> +
    >> + if (!bus || !bus->iommu_ops)
    >> + return NULL;
    >> +
    >> + cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);
    >> + if (!cookie)
    >> + return NULL;
    >> +
    >> + domain = bus->iommu_ops->domain_alloc(IOMMU_DOMAIN_SVA);
    >> + if (!domain)
    >> + goto err_domain_alloc;
    >> +
    >> + cookie->mm = mm;
    >> + cookie->pasid = mm->pasid;
    > How do you manage the mm life cycle? do you require caller take mm reference?
    > Or this should be limited to the current mm?
    >

    The existing sva_bind() interface requires the caller to take the mm
    reference before calling it. So mm is safe during sva bind() and
    unbind().

    drivers/iommu/iommu.c:
    /**
    * iommu_sva_bind_device() - Bind a process address space to a device
    * @dev: the device
    * @mm: the mm to bind, caller must hold a reference to it
    * @drvdata: opaque data pointer to pass to bind callback
    *
    * Create a bond between device and address space, allowing the device
    to access
    * the mm using the returned PASID. If a bond already exists between
    @device and
    * @mm, it is returned and an additional reference is taken. Caller
    must call
    * iommu_sva_unbind_device() to release each reference.
    *
    * iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) must be called
    first, to
    * initialize the required SVA features.
    *
    * On error, returns an ERR_PTR value.
    */
    struct iommu_sva *
    iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void
    *drvdata)

    Best regards,
    baolu

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