fhi_72: allow to provide dpdk_iova_mode to xran

In DPDK, IO Virtual Addresses (IOVA) refers to the memory addressing
scheme used for IO operations. The two IOVA modes supported by DPDK are:

- IOVA as Physical Address (PA): IO memory addresses correspond directly
  to physical addresses, no address translation required.
- IOVA as Virtual Address (VA): IO memory addresses align with user-space
  virtual addresses, requiring IOMMU to remap physical memory.

Previously, this was hardcoded to 0, to use IOVA as PA mode, with xRAN's
DPDK EAL initialization using the "--iova-mode=pa" flag.

This commit introduces a gNB configuration option to allow users to select
the desired IOVA mode. The default remains PA mode to
ensure backward compatibility.

Using IOVA VA mode allows DPDK to run without requiring SYS_ADMIN
capability in the docker container.

doc/ORAN_FHI7.2_Tutorial.md

@@ -917,6 +917,17 @@ Edit the sample OAI gNB configuration file and check following parameters:
     cannot preallocate memory on NUMA nodes other than 0; in this case, set
     this to 0 (no pre-allocation) and so that DPDK will allocate it on-demand
     on the right NUMA node.
+  * `dpdk_iova_mode`: Specifies DPDK IO Virtual Address (IOVA) mode:
+    * `PA`: IOVA as Physical Address (PA) mode, where DPDK IOVA memory layout
+      corresponds directly to the physical memory layout.
+    * `VA`: IOVA as Virtual Address (VA) mode, where DPDK IOVA addresses do not
+      follow the physical memory layout. Uses IOMMU to remap physical memory.
+      Requires kernel support and IOMMU for address translation.
+    * If not specified, default value of "PA" is used (for backwards compabilibity;
+      it was hardcoded to PA in the past). However, we recommend using "VA" mode
+      as it offers several benefits. For a detailed explanation of DPDK IOVA,
+      including the advantages and disadvantages of each mode, refer to
+      [Memory in DPDK](https://www.dpdk.org/memory-in-dpdk-part-2-deep-dive-into-iova/)
   * `owdm_enable`: used for eCPRI One-Way Delay Measurements; it depends if the RU supports it; if not set to 1 (enabled), default value is 0 (disabled)
   * `fh_config`: parameters that need to match RU parameters
     * timing parameters (starting with `T`) depend on the RU: `Tadv_cp_dl` is a

doc/tuning_and_security.md

@@ -146,6 +146,9 @@ on DPDK:
 - `IPC_LOCK` (becomes mandatory with DPDK)
 - `SYS_RESOURCE`
 - `NET_RAW`
+- `SYS_ADMIN`: This is required by DPDK when using IOVA PA (Physical Address)
+   mode to read `/proc/self/pagemaps`. However, if DPDK EAL is configured to use
+   IOVA VA (Virtual Address) mode, this capability is no longer required.
 
 ## Capabilities with UHD