xen/arm: Create a fake cpus node in dom0 device tree

The number of cpus in dom0 can be different compare to the real number of
physical cpus.

For the moment, Xen assumes that the cpus are identical.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

xen/arch/arm/domain_build.c

@@ -352,6 +352,93 @@ static int make_psci_node(void *fdt, const struct dt_device_node *parent)
     return res;
 }
 
+static int make_cpus_node(const struct domain *d, void *fdt,
+                          const struct dt_device_node *parent)
+{
+    int res;
+    const struct dt_device_node *cpus = dt_find_node_by_path("/cpus");
+    const struct dt_device_node *npcpu;
+    unsigned int cpu;
+    const void *compatible = NULL;
+    u32 len;
+    /* Placeholder for cpu@ + a 32-bit number + \0 */
+    char buf[15];
+
+    DPRINT("Create cpus node\n");
+
+    if ( !cpus )
+    {
+        dprintk(XENLOG_ERR, "Missing /cpus node in the device tree?\n");
+        return -ENOENT;
+    }
+
+    /*
+     * Get the compatible property of CPUs from the device tree.
+     * We are assuming that all CPUs are the same so we are just look
+     * for the first one.
+     * TODO: Handle compatible per VCPU
+     */
+    dt_for_each_child_node(cpus, npcpu)
+    {
+        if ( dt_device_type_is_equal(npcpu, "cpu") )
+        {
+            compatible = dt_get_property(npcpu, "compatible", &len);
+            break;
+        }
+    }
+
+    if ( !compatible )
+    {
+        dprintk(XENLOG_ERR, "Can't find cpu in the device tree?\n");
+        return -ENOENT;
+    }
+
+    /* See Linux Documentation/devicetree/booting-without-of.txt
+     * section III.5.b
+     */
+    res = fdt_begin_node(fdt, "cpus");
+    if ( res )
+        return res;
+
+    res = fdt_property_cell(fdt, "#address-cells", 1);
+    if ( res )
+        return res;
+
+    res = fdt_property_cell(fdt, "#size-cells", 0);
+    if ( res )
+        return res;
+
+    for ( cpu = 0; cpu < d->max_vcpus; cpu++ )
+    {
+        DPRINT("Create cpu@%u node\n", cpu);
+
+        snprintf(buf, sizeof(buf), "cpu@%u", cpu);
+        res = fdt_begin_node(fdt, buf);
+        if ( res )
+            return res;
+
+        res = fdt_property(fdt, "compatible", compatible, len);
+        if ( res )
+            return res;
+
+        res = fdt_property_string(fdt, "device_type", "cpu");
+        if ( res )
+            return res;
+
+        res = fdt_property_cell(fdt, "reg", cpu);
+        if ( res )
+            return res;
+
+        res = fdt_end_node(fdt);
+        if ( res )
+            return res;
+    }
+
+    res = fdt_end_node(fdt);
+
+    return res;
+}
+
 /* Map the device in the domain */
 static int map_device(struct domain *d, const struct dt_device_node *dev)
 {
@@ -440,6 +527,7 @@ static int handle_node(struct domain *d, struct kernel_info *kinfo,
         DT_MATCH_COMPATIBLE("xen,xen"),
         DT_MATCH_COMPATIBLE("xen,multiboot-module"),
         DT_MATCH_COMPATIBLE("arm,psci"),
+        DT_MATCH_PATH("/cpus"),
         { /* sentinel */ },
     };
     const struct dt_device_node *child;
@@ -509,6 +597,10 @@ static int handle_node(struct domain *d, struct kernel_info *kinfo,
         res = make_psci_node(kinfo->fdt, np);
         if ( res )
             return res;
+
+        res = make_cpus_node(d, kinfo->fdt, np);
+        if ( res )
+            return res;
     }
 
     res = fdt_end_node(kinfo->fdt);