RE: [PATCH v2 12/17] iommufd: Add iommufd_device_replace()

From: Jason Gunthorpe jgg@nvidia.com Sent: Wednesday, March 8, 2023 8:36 AM

@@ -359,6 +360,76 @@ iommufd_device_do_attach(struct iommufd_device *idev, return NULL; }

+static struct iommufd_hw_pagetable * +iommufd_device_do_replace(struct iommufd_device *idev,

• 	  struct iommufd_hw_pagetable *hwpt)
  

+{

• struct iommufd_group *igroup = idev->igroup;
• struct iommufd_hw_pagetable *old_hwpt;
• unsigned int num_devices = 0;
• struct iommufd_device *cur;
• int rc;
• mutex_lock(&idev->igroup->lock);
• if (hwpt == igroup->hwpt) {

• mutex_unlock(&idev->igroup->lock);
  

• return NULL;
  

• }
• /* Try to upgrade the domain we have */
• list_for_each_entry(cur, &igroup->device_list, group_item) {

• num_devices++;
  

• if (cur->enforce_cache_coherency) {
  

• 	rc = iommufd_hw_pagetable_enforce_cc(hwpt);
  

• 	if (rc)
  

• 		goto err_unlock;
  

• }
  

• }
• old_hwpt = igroup->hwpt;
• if (hwpt->ioas != old_hwpt->ioas) {

Do we allow this function to be used as attach/detach?

if yes old_hwpt could be NULL here.

if no an explicit check on old_hwpt!=NULL is also required.

and looks the policy for physical attach is different from the one that Nicoline applies for access. iommufd_access_set_ioas() can behave like normal attach/detach.

should be consistent here.