libxl: Add support for Device Tree passthrough

On ARM, every non-PCI device are described in the device tree. Each of
them can be found via a path.

This patch introduces a very basic support, only the IOMMU will be set
up correctly. The user will have to:
    - Describe the device in the partial device tree
    - Map manually MMIO/IRQ

This is a first approach, that will allow to have a basic Device Tree
passthrough support in Xen. This could be improved later.

Furthermore add LIBXL_HAVE_DEVICETREE_PASSTHROUGH to indicate we
support Device Tree passthrough and partial device tree (introduced by a
previous patch).

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>

tools/libxl/libxl.h

@@ -192,6 +192,13 @@
  * is not present, instead of ERROR_INVAL.
  */
 #define LIBXL_HAVE_ERROR_DOMAIN_NOTFOUND 1
+
+/*
+ * libxl_domain_build_info has device_tree and libxl_device_dtdev
+ * exists. This mean Device Tree passthrough is supported for ARM
+ */
+#define LIBXL_HAVE_DEVICETREE_PASSTHROUGH 1
+
 /*
  * libxl ABI compatibility
  *

tools/libxl/libxl_create.c

@@ -764,6 +764,8 @@ static void domcreate_attach_vtpms(libxl__egc *egc, libxl__multidev *multidev,
                                    int ret);
 static void domcreate_attach_pci(libxl__egc *egc, libxl__multidev *aodevs,
                                  int ret);
+static void domcreate_attach_dtdev(libxl__egc *egc,
+                                   libxl__domain_create_state *dcs);
 
 static void domcreate_console_available(libxl__egc *egc,
                                         libxl__domain_create_state *dcs);
@@ -1457,6 +1459,36 @@ static void domcreate_attach_pci(libxl__egc *egc, libxl__multidev *multidev,
         }
     }
 
+    domcreate_attach_dtdev(egc, dcs);
+    return;
+
+error_out:
+    assert(ret);
+    domcreate_complete(egc, dcs, ret);
+}
+
+static void domcreate_attach_dtdev(libxl__egc *egc,
+                                   libxl__domain_create_state *dcs)
+{
+    STATE_AO_GC(dcs->ao);
+    int i;
+    int ret;
+    int domid = dcs->guest_domid;
+
+    /* convenience aliases */
+    libxl_domain_config *const d_config = dcs->guest_config;
+
+    for (i = 0; i < d_config->num_dtdevs; i++) {
+        const libxl_device_dtdev *dtdev = &d_config->dtdevs[i];
+
+        LOG(DEBUG, "Assign device \"%s\" to dom%u", dtdev->path, domid);
+        ret = xc_assign_dt_device(CTX->xch, domid, dtdev->path);
+        if (ret < 0) {
+            LOG(ERROR, "xc_assign_dtdevice failed: %d\n", ret);
+            goto error_out;
+        }
+    }
+
     domcreate_console_available(egc, dcs);
 
     domcreate_complete(egc, dcs, 0);

tools/libxl/libxl_internal.h

@@ -1208,6 +1208,11 @@ _hidden int libxl__create_pci_backend(libxl__gc *gc, uint32_t domid,
                                       libxl_device_pci *pcidev, int num);
 _hidden int libxl__device_pci_destroy_all(libxl__gc *gc, uint32_t domid);
 
+/* from libxl_dtdev */
+
+_hidden int libxl__device_dt_add(libxl__gc *gc, uint32_t domid,
+                                 const libxl_device_dtdev *dtdev);
+
 /*----- xswait: wait for a xenstore node to be suitable -----*/
 
 typedef struct libxl__xswait_state libxl__xswait_state;

tools/libxl/libxl_types.idl

@@ -541,6 +541,10 @@ libxl_device_pci = Struct("device_pci", [
     ("seize", bool),
     ])
 
+libxl_device_dtdev = Struct("device_dtdev", [
+    ("path", string),
+    ])
+
 libxl_device_vtpm = Struct("device_vtpm", [
     ("backend_domid",    libxl_domid),
     ("backend_domname",  string),
@@ -567,6 +571,7 @@ libxl_domain_config = Struct("domain_config", [
     ("disks", Array(libxl_device_disk, "num_disks")),
     ("nics", Array(libxl_device_nic, "num_nics")),
     ("pcidevs", Array(libxl_device_pci, "num_pcidevs")),
+    ("dtdevs", Array(libxl_device_dtdev, "num_dtdevs")),
     ("vfbs", Array(libxl_device_vfb, "num_vfbs")),
     ("vkbs", Array(libxl_device_vkb, "num_vkbs")),
     ("vtpms", Array(libxl_device_vtpm, "num_vtpms")),