[RFC PATCH 20/21] libxl/arm: vIOMMU: Modify the partial device tree for iommus

[Rahul Singh <rahul.singh@xxxxxxx>]

To configure IOMMU in guest for passthrough devices, user will need to
copy the unmodified "iommus" property from host device tree to partial
device tree. To enable the dom0 linux kernel to confiure the IOMMU
correctly replace the phandle in partial device tree with virtual
IOMMU phandle when "iommus" property is set.

Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
---
 tools/libs/light/libxl_arm.c | 47 +++++++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
index f2bb7d40dc..16d068404f 100644
--- a/tools/libs/light/libxl_arm.c
+++ b/tools/libs/light/libxl_arm.c
@@ -1167,6 +1167,41 @@ static int copy_partial_fdt(libxl__gc *gc, void *fdt, 
void *pfdt)
     return 0;
 }
 
+static int modify_partial_fdt(libxl__gc *gc, void *pfdt)
+{
+    int nodeoff, proplen, i, r;
+    const fdt32_t *prop;
+    fdt32_t *prop_c;
+
+    nodeoff = fdt_path_offset(pfdt, "/passthrough");
+    if (nodeoff < 0)
+        return nodeoff;
+
+    for (nodeoff = fdt_first_subnode(pfdt, nodeoff);
+         nodeoff >= 0;
+         nodeoff = fdt_next_subnode(pfdt, nodeoff)) {
+
+        prop = fdt_getprop(pfdt, nodeoff, "iommus", &proplen);
+        if (!prop)
+            continue;
+
+        prop_c = libxl__zalloc(gc, proplen);
+
+        for (i = 0; i < proplen / 8; ++i) {
+            prop_c[i * 2] = cpu_to_fdt32(GUEST_PHANDLE_VSMMUV3);
+            prop_c[i * 2 + 1] = prop[i * 2 + 1];
+        }
+
+        r = fdt_setprop(pfdt, nodeoff, "iommus", prop_c, proplen);
+        if (r) {
+            LOG(ERROR, "Can't set the iommus property in partial FDT");
+            return r;
+        }
+    }
+
+    return 0;
+}
+
 #else
 
 static int check_partial_fdt(libxl__gc *gc, void *fdt, size_t size)
@@ -1185,6 +1220,13 @@ static int copy_partial_fdt(libxl__gc *gc, void *fdt, 
void *pfdt)
     return -FDT_ERR_INTERNAL;
 }
 
+static int modify_partial_fdt(libxl__gc *gc, void *pfdt)
+{
+    LOG(ERROR, "partial device tree not supported");
+
+    return ERROR_FAIL;
+}
+
 #endif /* ENABLE_PARTIAL_DEVICE_TREE */
 
 #define FDT_MAX_SIZE (1<<20)
@@ -1307,8 +1349,11 @@ next_resize:
         if (d_config->num_pcidevs)
             FDT( make_vpci_node(gc, fdt, ainfo, dom) );
 
-        if (info->arch_arm.viommu_type == LIBXL_VIOMMU_TYPE_SMMUV3)
+        if (info->arch_arm.viommu_type == LIBXL_VIOMMU_TYPE_SMMUV3) {
             FDT( make_vsmmuv3_node(gc, fdt, ainfo, dom) );
+            if (pfdt)
+                FDT( modify_partial_fdt(gc, pfdt) );
+        }
 
         iommu_created = false;
         for (i = 0; i < d_config->num_disks; i++) {
-- 
2.25.1