iommufd/device: Replace device_list with device_array

igroup->attach->device_list is used to track attached device of a group
in the RID path. Such tracking is also needed in the PASID path in order
to share path with the RID path.

While there is only one list_head in the iommufd_device. It cannot work
if the device has been attached in both RID path and PASID path. To solve
it, replacing the device_list with an xarray. The attached iommufd_device
is stored in the entry indexed by the idev->obj.id.

Link: https://patch.msgid.link/r/20250321171940.7213-9-yi.l.liu@intel.com
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 6b4764c2d9af62d73b34ba63738d87c30a3d7069..760917f5d7649d6878334a74d82c8d469ce146e9 100644 (file)
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -19,7 +19,7 @@ MODULE_PARM_DESC(
 
 struct iommufd_attach {
        struct iommufd_hw_pagetable *hwpt;
-       struct list_head device_list;
+       struct xarray device_array;
 };
 
 static void iommufd_group_release(struct kref *kref)
@@ -297,6 +297,20 @@ u32 iommufd_device_to_id(struct iommufd_device *idev)
 }
 EXPORT_SYMBOL_NS_GPL(iommufd_device_to_id, "IOMMUFD");
 
+static unsigned int iommufd_group_device_num(struct iommufd_group *igroup)
+{
+       struct iommufd_device *idev;
+       unsigned int count = 0;
+       unsigned long index;
+
+       lockdep_assert_held(&igroup->lock);
+
+       if (igroup->attach)
+               xa_for_each(&igroup->attach->device_array, index, idev)
+                       count++;
+       return count;
+}
+
 #ifdef CONFIG_IRQ_MSI_IOMMU
 static int iommufd_group_setup_msi(struct iommufd_group *igroup,
                                   struct iommufd_hwpt_paging *hwpt_paging)
@@ -371,12 +385,7 @@ iommufd_device_attach_reserved_iova(struct iommufd_device *idev,
 /* Check if idev is attached to igroup->hwpt */
 static bool iommufd_device_is_attached(struct iommufd_device *idev)
 {
-       struct iommufd_device *cur;
-
-       list_for_each_entry(cur, &idev->igroup->attach->device_list, group_item)
-               if (cur == idev)
-                       return true;
-       return false;
+       return xa_load(&idev->igroup->attach->device_array, idev->obj.id);
 }
 
 static int iommufd_hwpt_attach_device(struct iommufd_hw_pagetable *hwpt,
@@ -510,20 +519,27 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
                        rc = -ENOMEM;
                        goto err_unlock;
                }
-               INIT_LIST_HEAD(&attach->device_list);
+               xa_init(&attach->device_array);
        }
 
        old_hwpt = attach->hwpt;
 
+       rc = xa_insert(&attach->device_array, idev->obj.id, XA_ZERO_ENTRY,
+                      GFP_KERNEL);
+       if (rc) {
+               WARN_ON(rc == -EBUSY && !old_hwpt);
+               goto err_free_attach;
+       }
+
        if (old_hwpt && old_hwpt != hwpt) {
                rc = -EINVAL;
-               goto err_free_attach;
+               goto err_release_devid;
        }
 
        if (attach_resv) {
                rc = iommufd_device_attach_reserved_iova(idev, hwpt_paging);
                if (rc)
-                       goto err_free_attach;
+                       goto err_release_devid;
        }
 
        /*
@@ -541,12 +557,15 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
                igroup->attach = attach;
        }
        refcount_inc(&hwpt->obj.users);
-       list_add_tail(&idev->group_item, &attach->device_list);
+       WARN_ON(xa_is_err(xa_store(&attach->device_array, idev->obj.id,
+                                  idev, GFP_KERNEL)));
        mutex_unlock(&igroup->lock);
        return 0;
 err_unresv:
        if (attach_resv)
                iopt_remove_reserved_iova(&hwpt_paging->ioas->iopt, idev->dev);
+err_release_devid:
+       xa_release(&attach->device_array, idev->obj.id);
 err_free_attach:
        if (iommufd_group_first_attach(igroup, pasid))
                kfree(attach);
@@ -568,8 +587,8 @@ iommufd_hw_pagetable_detach(struct iommufd_device *idev, ioasid_t pasid)
        hwpt = attach->hwpt;
        hwpt_paging = find_hwpt_paging(hwpt);
 
-       list_del(&idev->group_item);
-       if (list_empty(&attach->device_list)) {
+       xa_erase(&attach->device_array, idev->obj.id);
+       if (xa_empty(&attach->device_array)) {
                iommufd_hwpt_detach_device(hwpt, idev, pasid);
                igroup->attach = NULL;
                kfree(attach);
@@ -599,10 +618,11 @@ iommufd_group_remove_reserved_iova(struct iommufd_group *igroup,
                                   struct iommufd_hwpt_paging *hwpt_paging)
 {
        struct iommufd_device *cur;
+       unsigned long index;
 
        lockdep_assert_held(&igroup->lock);
 
-       list_for_each_entry(cur, &igroup->attach->device_list, group_item)
+       xa_for_each(&igroup->attach->device_array, index, cur)
                iopt_remove_reserved_iova(&hwpt_paging->ioas->iopt, cur->dev);
 }
 
@@ -612,14 +632,14 @@ iommufd_group_do_replace_reserved_iova(struct iommufd_group *igroup,
 {
        struct iommufd_hwpt_paging *old_hwpt_paging;
        struct iommufd_device *cur;
+       unsigned long index;
        int rc;
 
        lockdep_assert_held(&igroup->lock);
 
        old_hwpt_paging = find_hwpt_paging(igroup->attach->hwpt);
        if (!old_hwpt_paging || hwpt_paging->ioas != old_hwpt_paging->ioas) {
-               list_for_each_entry(cur,
-                                   &igroup->attach->device_list, group_item) {
+               xa_for_each(&igroup->attach->device_array, index, cur) {
                        rc = iopt_table_enforce_dev_resv_regions(
                                &hwpt_paging->ioas->iopt, cur->dev, NULL);
                        if (rc)
@@ -660,7 +680,7 @@ iommufd_device_do_replace(struct iommufd_device *idev, ioasid_t pasid,
 
        old_hwpt = attach->hwpt;
 
-       WARN_ON(!old_hwpt || list_empty(&attach->device_list));
+       WARN_ON(!old_hwpt || xa_empty(&attach->device_array));
 
        if (!iommufd_device_is_attached(idev)) {
                rc = -EINVAL;
@@ -689,9 +709,9 @@ iommufd_device_do_replace(struct iommufd_device *idev, ioasid_t pasid,
 
        attach->hwpt = hwpt;
 
-       num_devices = list_count_nodes(&attach->device_list);
+       num_devices = iommufd_group_device_num(igroup);
        /*
-        * Move the refcounts held by the device_list to the new hwpt. Retain a
+        * Move the refcounts held by the device_array to the new hwpt. Retain a
         * refcount for this thread as the caller will free it.
         */
        refcount_add(num_devices, &hwpt->obj.users);