[Xen-devel] [PATCH V3 7/8] iommu/arm: Introduce iommu_add_dt_device API

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

This patch adds new iommu_add_dt_device API for adding DT device
to the IOMMU using generic IOMMU DT bindings [1] and previously
added "iommu_fwspec" support and "add_device/of_xlate" callbacks.

New function does the following:
- Parse the DT bindings according to the specification
- Provide DT IOMMU specifier which describes the IOMMU master
  interfaces of that device (device IDs, etc) to the driver
- Add master device to the IOMMU if latter is present and available

The additional benefit here is to avoid to go through the whole DT
multiple times in IOMMU driver trying to locate master devices which
belong to each IOMMU device being probed.

[1] https://www.kernel.org/doc/Documentation/devicetree/bindings/iommu/iommu.txt

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>

---
Changes V2 -> V3:
    - clarified patch description
    - clarified comments in code
    - modified to provide DT IOMMU specifier to the driver
      using "of_xlate" callback
    - documented function usage
    - modified to return an error if ops is not present/implemented,
    - added ability to return a possitive value to indicate
      that device doesn't need to be protected
    - removed check for the "iommu" property presence
      in the common code
    - included <asm/iommu_fwspec.h> directly
---
 xen/arch/arm/domain_build.c         | 11 ++++++++
 xen/drivers/passthrough/arm/iommu.c | 55 +++++++++++++++++++++++++++++++++++++
 xen/include/asm-arm/iommu.h         | 11 ++++++++
 3 files changed, 77 insertions(+)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index e79d4e2..159ea6a 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -1240,6 +1240,7 @@ static int __init map_device_children(struct domain *d,
 
 /*
  * For a given device node:
+ *  - Try to call iommu_add_dt_device to protect the device by an IOMMU
  *  - 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:
@@ -1257,6 +1258,16 @@ static int __init handle_device(struct domain *d, struct 
dt_device_node *dev,
     u64 addr, size;
     bool need_mapping = !dt_device_for_passthrough(dev);
 
+    dt_dprintk("%s add to iommu\n", dt_node_full_name(dev));
+
+    res = iommu_add_dt_device(dev);
+    if ( res < 0 )
+    {
+        printk(XENLOG_ERR "Failed to add %s to the IOMMU\n",
+               dt_node_full_name(dev));
+        return res;
+    }
+
     nirq = dt_number_of_irq(dev);
     naddr = dt_number_of_address(dev);
 
diff --git a/xen/drivers/passthrough/arm/iommu.c 
b/xen/drivers/passthrough/arm/iommu.c
index 72a30e0..47e4bc6 100644
--- a/xen/drivers/passthrough/arm/iommu.c
+++ b/xen/drivers/passthrough/arm/iommu.c
@@ -20,6 +20,7 @@
 #include <xen/lib.h>
 
 #include <asm/device.h>
+#include <asm/iommu_fwspec.h>
 
 /*
  * Deferred probe list is used to keep track of devices for which driver
@@ -139,3 +140,57 @@ int arch_iommu_populate_page_table(struct domain *d)
 void __hwdom_init arch_iommu_hwdom_init(struct domain *d)
 {
 }
+
+int __init 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 || !ops->add_device || !ops->of_xlate )
+        return -EINVAL;
+
+    if ( dev_iommu_fwspec_get(dev) )
+        return -EEXIST;
+
+    /* According Documentation/devicetree/bindings/iommu/iommu.txt from Linux 
*/
+    while ( !dt_parse_phandle_with_args(np, "iommus", "#iommu-cells",
+                                        index, &iommu_spec) )
+    {
+        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's responsibility is to decide how to interpret them.
+         * It should also initialize/verify that device.
+         */
+        rc = ops->of_xlate(dev, &iommu_spec);
+        if ( rc )
+            break;
+
+        index++;
+    }
+
+    /*
+     * Add master device to the IOMMU if latter is present and available.
+     * The driver's responsibility is to check whether that device
+     * was initialized/verified before and mark that device as protected.
+     */
+    if ( !rc )
+        rc = ops->add_device(0, dev);
+
+    if ( rc < 0 )
+        iommu_fwspec_free(dev);
+
+    return rc;
+}
diff --git a/xen/include/asm-arm/iommu.h b/xen/include/asm-arm/iommu.h
index 20d865e..e75359c 100644
--- a/xen/include/asm-arm/iommu.h
+++ b/xen/include/asm-arm/iommu.h
@@ -26,6 +26,17 @@ struct arch_iommu
 const struct iommu_ops *iommu_get_ops(void);
 void iommu_set_ops(const struct iommu_ops *ops);
 
+/*
+ * 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);
+
 /* mapping helpers */
 int __must_check arm_iommu_map_page(struct domain *d, dfn_t dfn, mfn_t mfn,
                                     unsigned int flags,
-- 
2.7.4


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