On Tue, May 10, 2022 at 02:17:34PM +0800, Lu Baolu wrote:
> +/**
> + * 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 mm_users
> + * @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)
> +{
> + int ret = -EINVAL;
> + struct iommu_sva *handle;
> + struct iommu_domain *domain;
> +
> + /*
> + * TODO: Remove the drvdata parameter after kernel PASID support is
> + * enabled for the idxd driver.
> + */
> + if (drvdata)
> + return ERR_PTR(-EOPNOTSUPP);
Why is this being left behind? Clean up the callers too please.
> + /* Allocate mm->pasid if necessary. */
> + ret = iommu_sva_alloc_pasid(mm, 1, (1U << dev->iommu->pasid_bits) - 1);
> + if (ret)
> + return ERR_PTR(ret);
> +
> + mutex_lock(&iommu_sva_lock);
> + /* Search for an existing bond. */
> + handle = xa_load(&dev->iommu->sva_bonds, mm->pasid);
> + if (handle) {
> + refcount_inc(&handle->users);
> + goto out_success;
> + }
How can there be an existing bond?
dev->iommu is per-device
The device_group_immutable_singleton() insists on a single device
group
Basically 'sva_bonds' is the same thing as the group->pasid_array.
Assuming we leave room for multi-device groups this logic should just
be
group = iommu_group_get(dev);
if (!group)
return -ENODEV;
mutex_lock(&group->mutex);
domain = xa_load(&group->pasid_array, mm->pasid);
if (!domain || domain->type != IOMMU_DOMAIN_SVA || domain->mm != mm)
domain = iommu_sva_alloc_domain(dev, mm);
?
And stick the refcount in the sva_domain
Also, given the current arrangement it might make sense to have a
struct iommu_domain_sva given that no driver is wrappering this in
something else.
Jason
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