update(ipc): include note regarding to base and size

Signed-off-by: Diogo Costa <diogoandreveigacosta@gmail.com>

source/bao_hyp/config.rst

@@ -291,15 +291,15 @@ Inter-Process Communication (IPC) enables seamless communication between distinc
 computing system. This mechanism facilitates data exchange, synchronization, and coordination,
 fostering enhanced functionality and system efficiency.
 
+.. figure:: img/ipc.svg
+    :align: center
+    :name: ipc-fig
+
 Bao provides support for IPC, allowing VMs to establish communication channels. The IPC
 configuration involves defining the number of IPCs using the ``ipc_num`` field within the
 ``vm_config`` struct. The specifics of each IPC are then outlined through the ``ipcs`` structure,
 including fields such as ``base``, ``size``, ``shmem_id``, ``interrupt_num``, and ``interrupts``.
 
-.. figure:: img/ipc.svg
-    :align: center
-    :name: ipc-fig
-
 - **ipc_num** [optional] - defines the number of IPCs assigned to the VM. By default, ``ipc_num``
   equals to zero;
 - **ipcs** [mandatory if ``ipc_num`` > 0] - corresponds to the specification of the IPC and is
@@ -361,6 +361,11 @@ where:
 - **pa** [mandatory] - corresponds to the base physical address of the device;
 - **va** [mandatory] - corresponds to the base virtual address of the device;
 - **size** [mandatory] - corresponds to the size of the device memory region;
+
+.. note::
+  It is mandatory for `base` and `size` to align with the smallest page size of the architecture.
+  For MMU systems, this typically aligns to 4K, while for MPU systems, it aligns to 64 bytes.
+
 - **interrupt_num** [optional] - corresponds to the number of interrupts generated by the device to
   the VM. By default, ``interrupt_num`` equals to 0;
 - **interrupts** [mandatory if *interrupt_num*>0] - defines a list of interrupt IDs generated by