Re: [PATCH v5 1/9] iommu: Introduce domain attachment handle

[Baolu Lu]

On 5/15/24 3:17 PM, Tian, Kevin wrote:

From: Lu Baolu <baolu...@linux.intel.com>
Sent: Tuesday, April 30, 2024 10:57 PM

+/* Add an attach handle to the group's pasid array. */
+static struct iommu_attach_handle *
+iommu_attach_handle_set(struct iommu_domain *domain,
+                       struct iommu_group *group, ioasid_t pasid)
+{
+       struct iommu_attach_handle *handle;
+       void *curr;
+
+       handle = kzalloc(sizeof(*handle), GFP_KERNEL);
+       if (!handle)
+               return ERR_PTR(-ENOMEM);
+
+       handle->domain = domain;
+       curr = xa_cmpxchg(&group->pasid_array, pasid, NULL, handle,
GFP_KERNEL);

this could be just xa_insert() which returns -EBUSY if the entry isn't NULL.

Yes, exactly.

+       if (curr) {
+               kfree(handle);
+               return xa_err(curr) ? curr : ERR_PTR(-EBUSY);

'curr' is not an error pointer. You need ERR_PTR(xa_err(curr)).

Fixed.

  int iommu_attach_group(struct iommu_domain *domain, struct
iommu_group *group)
  {
+       struct iommu_attach_handle *handle;
        int ret;

        mutex_lock(&group->mutex);
+       handle = iommu_attach_handle_set(domain, group,
IOMMU_NO_PASID);
+       if (IS_ERR(handle)) {
+               ret = PTR_ERR(handle);
+               goto out_unlock;
+       }
        ret = __iommu_attach_group(domain, group);
+       if (ret)
+               goto out_remove_handle;
        mutex_unlock(&group->mutex);

It's slightly better to set the handler after __iommu_attach_group().

doing so is aligned to the sequence in iommu_group_replace_domain().

I did it in this way because erasing an attach handle is easier than
rolling back the group to the previous domain from the perspective of
coding. I didn't realize attaching the group and storing the attach
handle had to be done in a specific order.

@@ -2211,13 +2307,33 @@ EXPORT_SYMBOL_GPL(iommu_attach_group);
  int iommu_group_replace_domain(struct iommu_group *group,
                               struct iommu_domain *new_domain)
  {
+       struct iommu_domain *old_domain = group->domain;
+       struct iommu_attach_handle *handle;
        int ret;

        if (!new_domain)
                return -EINVAL;

+       if (new_domain == old_domain)
+               return 0;
+

__iommu_group_set_domain() already does the check.

Removed.

Best regards,
baolu