iommu/arm: Introduce iommu_add_dt_device API

The main puprose of this patch is to add a way to register DT device
(which is behind the IOMMU) using the generic IOMMU DT bindings [1]
before assigning that device to a domain.

So, this patch adds new "iommu_add_dt_device" API for adding DT device
to the IOMMU using generic IOMMU DT bindings and previously added
"iommu_fwspec" support. As devices can be assigned to the hardware domain
and other domains this function is called from two places: handle_device()
and iommu_do_dt_domctl().

Besides that, this patch adds new "dt_xlate" callback (borrowed from
Linux "of_xlate") for providing the driver with DT IOMMU specifier
which describes the IOMMU master interfaces of that device (device IDs, etc).
According to the generic IOMMU DT bindings the context of required
properties for IOMMU device/master node (#iommu-cells, iommus) depends
on many factors and is really driver depended thing.

Please note, all IOMMU drivers which support generic IOMMU DT bindings
should use "dt_xlate" and "add_device" callbacks.

[1] https://www.kernel.org/doc/Documentation/devicetree/bindings/iommu/iommu.txtSigned-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Acked-by: Julien Grall <julien.grall@arm.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/arm/domain_build.c

@@ -1243,6 +1243,7 @@ static int __init map_device_children(struct domain *d,
  *  - Give permission to the guest to manage IRQ and MMIO range
  *  - Retrieve the IRQ configuration (i.e edge/level) from device tree
  * When the device is not marked for guest passthrough:
+ *  - Try to call iommu_add_dt_device to protect the device by an IOMMU
  *  - Assign the device to the guest if it's protected by an IOMMU
  *  - Map the IRQs and iomem regions to DOM0
  */
@@ -1263,16 +1264,30 @@ static int __init handle_device(struct domain *d, struct dt_device_node *dev,
     dt_dprintk("%s passthrough = %d nirq = %d naddr = %u\n",
                dt_node_full_name(dev), need_mapping, nirq, naddr);
 
-    if ( dt_device_is_protected(dev) && need_mapping )
+    if ( need_mapping )
     {
-        dt_dprintk("%s setup iommu\n", dt_node_full_name(dev));
-        res = iommu_assign_dt_device(d, dev);
-        if ( res )
+        dt_dprintk("Check if %s is behind the IOMMU and add it\n",
+                   dt_node_full_name(dev));
+
+        res = iommu_add_dt_device(dev);
+        if ( res < 0 )
         {
-            printk(XENLOG_ERR "Failed to setup the IOMMU for %s\n",
+            printk(XENLOG_ERR "Failed to add %s to the IOMMU\n",
                    dt_node_full_name(dev));
             return res;
         }
+
+        if ( dt_device_is_protected(dev) )
+        {
+            dt_dprintk("%s setup iommu\n", dt_node_full_name(dev));
+            res = iommu_assign_dt_device(d, dev);
+            if ( res )
+            {
+                printk(XENLOG_ERR "Failed to setup the IOMMU for %s\n",
+                       dt_node_full_name(dev));
+                return res;
+            }
+        }
     }
 
     /* Give permission and map IRQs */

xen/drivers/passthrough/device_tree.c

@@ -22,6 +22,8 @@
 #include <xen/sched.h>
 #include <xsm/xsm.h>
 
+#include <asm/iommu_fwspec.h>
+
 static spinlock_t dtdevs_lock = SPIN_LOCK_UNLOCKED;
 
 int iommu_assign_dt_device(struct domain *d, struct dt_device_node *dev)
@@ -125,6 +127,68 @@ int iommu_release_dt_devices(struct domain *d)
     return 0;
 }
 
+int iommu_add_dt_device(struct dt_device_node *np)
+{
+    const struct iommu_ops *ops = iommu_get_ops();
+    struct dt_phandle_args iommu_spec;
+    struct device *dev = dt_to_dev(np);
+    int rc = 1, index = 0;
+
+    if ( !iommu_enabled )
+        return 1;
+
+    if ( !ops )
+        return -EINVAL;
+
+    if ( dev_iommu_fwspec_get(dev) )
+        return -EEXIST;
+
+    /*
+     * According to the Documentation/devicetree/bindings/iommu/iommu.txt
+     * from Linux.
+     */
+    while ( !dt_parse_phandle_with_args(np, "iommus", "#iommu-cells",
+                                        index, &iommu_spec) )
+    {
+        /*
+         * The driver which supports generic IOMMU DT bindings must have
+         * these callback implemented.
+         */
+        if ( !ops->add_device || !ops->dt_xlate )
+            return -EINVAL;
+
+        if ( !dt_device_is_available(iommu_spec.np) )
+            break;
+
+        rc = iommu_fwspec_init(dev, &iommu_spec.np->dev);
+        if ( rc )
+            break;
+
+        /*
+         * Provide DT IOMMU specifier which describes the IOMMU master
+         * interfaces of that device (device IDs, etc) to the driver.
+         * The driver is responsible to decide how to interpret them.
+         */
+        rc = ops->dt_xlate(dev, &iommu_spec);
+        if ( rc )
+            break;
+
+        index++;
+    }
+
+    /*
+     * Add master device to the IOMMU if latter is present and available.
+     * The driver is responsible to mark that device as protected.
+     */
+    if ( !rc )
+        rc = ops->add_device(0, dev);
+
+    if ( rc < 0 )
+        iommu_fwspec_free(dev);
+
+    return rc;
+}
+
 int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d,
                        XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
 {
@@ -166,6 +230,19 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d,
             break;
         }
 
+        ret = iommu_add_dt_device(dev);
+        /*
+         * Ignore "-EEXIST" error code as it would mean that the device is
+         * already added to the IOMMU (positive result). Such happens after
+         * re-creating guest domain.
+         */
+        if ( ret < 0 && ret != -EEXIST )
+        {
+            printk(XENLOG_G_ERR "Failed to add %s to the IOMMU\n",
+                   dt_node_full_name(dev));
+            break;
+        }
+
         ret = iommu_assign_dt_device(d, dev);
 
         if ( ret )

xen/include/xen/iommu.h

@@ -182,6 +182,17 @@ 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);
 
+/*
+ * Helper to add master device to the IOMMU using generic IOMMU DT bindings.
+ *
+ * Return values:
+ *  0 : device is protected by an IOMMU
+ * <0 : device is not protected by an IOMMU, but must be (error condition)
+ * >0 : device doesn't need to be protected by an IOMMU
+ *      (IOMMU is not enabled/present or device is not connected to it).
+ */
+int iommu_add_dt_device(struct dt_device_node *np);
+
 int iommu_do_dt_domctl(struct xen_domctl *, struct domain *,
                        XEN_GUEST_HANDLE_PARAM(xen_domctl_t));
 
@@ -250,6 +261,16 @@ struct iommu_ops {
     int __must_check (*iotlb_flush_all)(struct domain *d);
     int (*get_reserved_device_memory)(iommu_grdm_t *, void *);
     void (*dump_p2m_table)(struct domain *d);
+
+#ifdef CONFIG_HAS_DEVICE_TREE
+    /*
+     * All IOMMU drivers which support generic IOMMU DT bindings should use
+     * this callback. This is a way for the framework to provide the driver
+     * with DT IOMMU specifier which describes the IOMMU master interfaces of
+     * that device (device IDs, etc).
+     */
+    int (*dt_xlate)(device_t *dev, const struct dt_phandle_args *args);
+#endif
 };
 
 #include <asm/iommu.h>