Rename iommu_dt_device_is_assigned() to iommu_dt_device_is_assigned_locked().
Remove static type so this can also be used by SMMU drivers to check if the
device is being used before removing.

Moving spin_lock to caller was done to prevent the concurrent access to
iommu_dt_device_is_assigned while doing add/remove/assign/deassign.

Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
---
 xen/drivers/passthrough/device_tree.c | 19 +++++++++++++++----
 xen/include/xen/iommu.h               |  1 +
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/xen/drivers/passthrough/device_tree.c b/xen/drivers/passthrough/device_tree.c
index 1c32d7b50c..c386fda3e4 100644
--- a/xen/drivers/passthrough/device_tree.c
+++ b/xen/drivers/passthrough/device_tree.c
@@ -83,16 +83,14 @@ fail:
     return rc;
 }
 
-static bool_t iommu_dt_device_is_assigned(const struct dt_device_node *dev)
+bool_t iommu_dt_device_is_assigned_locked(const struct dt_device_node *dev)
 {
     bool_t assigned = 0;
 
     if ( !dt_device_is_protected(dev) )
         return 0;
 
-    spin_lock(&dtdevs_lock);
     assigned = !list_empty(&dev->domain_list);
-    spin_unlock(&dtdevs_lock);
 
     return assigned;
 }
@@ -213,27 +211,40 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d,
         if ( (d && d->is_dying) || domctl->u.assign_device.flags )
             break;
 
+        spin_lock(&dtdevs_lock);
+
         ret = dt_find_node_by_gpath(domctl->u.assign_device.u.dt.path,
                                     domctl->u.assign_device.u.dt.size,
                                     &dev);
         if ( ret )
+        {
+            spin_unlock(&dtdevs_lock);
             break;
+        }
 
         ret = xsm_assign_dtdevice(XSM_HOOK, d, dt_node_full_name(dev));
         if ( ret )
+        {
+            spin_unlock(&dtdevs_lock);
             break;
+        }
 
         if ( domctl->cmd == XEN_DOMCTL_test_assign_device )
         {
-            if ( iommu_dt_device_is_assigned(dev) )
+
+            if ( iommu_dt_device_is_assigned_locked(dev) )
             {
                 printk(XENLOG_G_ERR "%s already assigned.\n",
                        dt_node_full_name(dev));
                 ret = -EINVAL;
             }
+
+            spin_unlock(&dtdevs_lock);
             break;
         }
 
+        spin_unlock(&dtdevs_lock);
+
         if ( d == dom_io )
             return -EINVAL;
 
diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index 405db59971..76add226ec 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -214,6 +214,7 @@ struct msi_msg;
 #include <xen/device_tree.h>
 
 int iommu_assign_dt_device(struct domain *d, struct dt_device_node *dev);
+bool_t iommu_dt_device_is_assigned_locked(const struct dt_device_node *dev);
 int iommu_deassign_dt_device(struct domain *d, struct dt_device_node *dev);
 int iommu_dt_domain_init(struct domain *d);
 int iommu_release_dt_devices(struct domain *d);
-- 
2.17.1

On 03.05.2023 01:36, Vikram Garhwal wrote:
> --- a/xen/include/xen/iommu.h
> +++ b/xen/include/xen/iommu.h
> @@ -214,6 +214,7 @@ struct msi_msg;
>  #include <xen/device_tree.h>
>  
>  int iommu_assign_dt_device(struct domain *d, struct dt_device_node *dev);
> +bool_t iommu_dt_device_is_assigned_locked(const struct dt_device_node *dev);

Hmm, exposing a function globally which, first and foremost because of
requiring the caller to hold the correct lock(s), is pretty much
internal, doesn't look very nice to me. Can this perhaps be put in a
private header, such that it gets only limited visibility?

Jan