[Xen-devel] [PATCH v7 3/6] tools/libxl: arm: Use an higher value for the GIC phandle

[Julien Grall <julien.grall@xxxxxxxxxx>]

From: Julien Grall <julien.grall@xxxxxxxxxx>

The partial device tree may contains phandle. The Device Tree Compiler
tends to allocate the phandle from 1.

Reserve the ID 65000 for the GIC phandle. I think we can safely assume
that the partial device tree will never contain a such ID.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>

---
    To allocate dynamically the phandle, we would need to fill in
    post-hoc (like we do with e.g the initramfs location) the
    #interrupt-parent in "/". That would also require some refactoring
    in the code to pass the phandle every time.

    Defer this solution to a follow-up in order as having 65000 would be
    very unlikely.

    Changes in v6:
        - Add a note in the doc about the reserved phandle

    Changes in v5:
        - Add Ian C.'s Ack.

    Changes in v3:
        - Patch added
---
 docs/man/xl.cfg.pod.5       | 3 +++
 tools/libxl/libxl_arm.c     | 9 +++++----
 tools/libxl/libxl_types.idl | 2 ++
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
index ead8a5c..fb8721f 100644
--- a/docs/man/xl.cfg.pod.5
+++ b/docs/man/xl.cfg.pod.5
@@ -470,6 +470,9 @@ the user to defined aliases which can be used by the guest 
kernel.
 Given the complexity of verifying the validity of a device tree, this
 option should only be used with trusted device tree.
 
+Note that the partial device tree should avoid to use the phandle 65000
+which is reserved by the toolstack.
+
 =back
 
 =head2 Devices
diff --git a/tools/libxl/libxl_arm.c b/tools/libxl/libxl_arm.c
index 6ad8b21..e144535 100644
--- a/tools/libxl/libxl_arm.c
+++ b/tools/libxl/libxl_arm.c
@@ -81,10 +81,11 @@ static struct arch_info {
     {"xen-3.0-aarch64", "arm,armv8-timer", "arm,armv8" },
 };
 
-enum {
-    PHANDLE_NONE = 0,
-    PHANDLE_GIC,
-};
+/*
+ * The device tree compiler (DTC) is allocating the phandle from 1 to
+ * onwards. Reserve a high value for the GIC phandle.
+ */
+#define PHANDLE_GIC (65000)
 
 typedef uint32_t be32;
 typedef be32 gic_interrupt[3];
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 2b57785..3254617 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -416,6 +416,8 @@ libxl_domain_build_info = Struct("domain_build_info",[
     # Given the complexity of verifying the validity of a device tree,
     # libxl doesn't do any security check on it. It's the responsibility
     # of the caller to provide only trusted device tree.
+    # Note that the partial device tree should avoid to use the phandle
+    # 65000 which is reserved by the toolstack.
     ("device_tree",      string),
     ("u", KeyedUnion(None, libxl_domain_type, "type",
                 [("hvm", Struct(None, [("firmware",         string),
-- 
2.1.4


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