[XEN][PATCH v6 09/19] xen/iommu: Move spin_lock from iommu_dt_device_is_assigned to caller

[Vikram Garhwal <vikram.garhwal@xxxxxxx>]

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@xxxxxxx>
Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>
---
 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