[PATCH v4 2/2] doc: add a guide doc for cross compiling from x86

[Gavin Hu <gavin.hu@arm.com>]

This is the guide for cross compiling ARM64 DPDK from X86 hosts.

Signed-off-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Steve Capper <Steve.Capper@arm.com>
Reviewed-by: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
Reviewed-by: Marko Kovacevic <marko.kovacevic@intel.com>
Reviewed-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Reviewed-by: Thomas Monjalon <thomas@monjalon.net>
Reviewed-by: Bruce Richardson <bruce.richardson@intel.com>
---
 .../linux_gsg/cross_build_dpdk_for_arm64.rst       | 125 +++++++++++++++++++++
 doc/guides/linux_gsg/index.rst                     |   1 +
 2 files changed, 126 insertions(+)
 create mode 100644 doc/guides/linux_gsg/cross_build_dpdk_for_arm64.rst

diff --git a/doc/guides/linux_gsg/cross_build_dpdk_for_arm64.rst b/doc/guides/linux_gsg/cross_build_dpdk_for_arm64.rst
new file mode 100644
index 0000000..f97b931
--- /dev/null
+++ b/doc/guides/linux_gsg/cross_build_dpdk_for_arm64.rst
@@ -0,0 +1,125 @@
+..  SPDX-License-Identifier: BSD-3-Clause
+    Copyright(c) 2018 ARM Corporation.
+
+Cross compile DPDK for ARM64
+============================
+This chapter describes how to cross compile DPDK for ARM64 from x86 build hosts.
+
+.. note::
+
+   Whilst it is recommended to natively build DPDK on ARM64 (just
+   like with x86), it is also possible to cross-build DPDK for ARM64. An
+   ARM64 cross compile GNU toolchain is used for this.
+
+Obtain the cross tool chain
+---------------------------
+The latest cross compile tool chain can be downloaded from:
+https://releases.linaro.org/components/toolchain/binaries/latest/aarch64-linux-gnu/.
+Following is the step to get the version 7.2.1, latest one at the time of this writing.
+
+.. code-block:: console
+
+   wget https://releases.linaro.org/components/toolchain/binaries/latest/
+   aarch64-linux-gnu/gcc-linaro-7.2.1-2017.11-x86_64_aarch64-linux-gnu.tar.xz
+
+Unzip and add into the PATH
+---------------------------
+
+.. code-block:: console
+
+   tar -xvf gcc-linaro-7.2.1-2017.11-x86_64_aarch64-linux-gnu.tar.xz
+   export PATH=$PATH:<cross_install_dir>/gcc-linaro-7.2.1-2017.11-x86_64
+   _aarch64-linux-gnu/bin
+
+.. note::
+
+   For the host requirements and other info, refer to the release note section:
+   https://releases.linaro.org/components/toolchain/binaries/latest/
+
+Getting the prerequisite library
+--------------------------------
+
+NUMA is required by most modern machines, not needed for non-NUMA archtectures.
+
+.. note::
+
+   For compiling the NUMA lib, run libtool --version to ensure the libtool version >= 2.2,
+   otherwise the compilation will fail with errors.
+
+.. code-block:: console
+
+   git clone https://github.com/numactl/numactl.git
+   cd numactl
+   git checkout v2.0.11 -b v2.0.11
+   ./autogen.sh
+   autoconf -i
+   ./configure --host=x86_64 CC=aarch64-linux-gnu-gcc prefix=<numa install dir>
+   make install
+
+The numa header files and lib file is generated in the include and lib folder respectively under <numa install dir>.
+
+.. _augument_the_cross_toolcain_with_numa_support:
+
+Augument the cross toolchain with NUMA support
+----------------------------------------------
+
+.. note::
+
+   This way is optional, an alternative is to use extra CFLAGS and LDFLAGS, depicted in :ref:`configure_and_cross_compile_dpdk_build` below.
+
+Copy the NUMA header files to the cross compiler's include directory:
+
+.. code-block:: console
+
+   cp <numa_install_dir>/include/numa*.h <cross_install_dir>/gcc-linaro-7.2.1-2017.11
+   -x86_64_aarch64-linux-gnu/bin/../aarch64-linux-gnu/libc/usr/include/
+   cp <numa_install_dir>/lib/libnuma.a <cross_install_dir>/gcc-linaro-7.2.1-2017.11
+   -x86_64_aarch64-linux-gnu/lib/gcc/aarch64-linux-gnu/7.2.1/
+
+.. _configure_and_cross_compile_dpdk_build:
+
+Configure and cross compile DPDK Build
+--------------------------------------
+To configure a build, choose one of the target configurations, like arm64-dpaa2-linuxapp-gcc and arm64-thunderx-linuxapp-gcc.
+
+.. code-block:: console
+
+   make config T=arm64-armv8a-linuxapp-gcc
+
+To cross-compile, without compiling the kernel modules, use the following command:
+
+.. code-block:: console
+
+   make -j CROSS=aarch64-linux-gnu- CONFIG_RTE_KNI_KMOD=n CONFIG_RTE_EAL_IGB_UIO=n
+
+To cross-compile, including the kernel modules, the kernel source tree needs to be specified by setting
+RTE_KERNELDIR:
+
+.. code-block:: console
+
+   make -j CROSS=aarch64-linux-gnu- RTE_KERNELDIR=<kernel_src_rootdir>
+   CROSS_COMPILE=aarch64-linux-gnu-
+
+To compile for non-NUMA targets, without compiling the kernel modules, use the following command:
+
+.. code-block:: console
+
+   make -j CROSS=aarch64-linux-gnu- CONFIG_RTE_KNI_KMOD=n CONFIG_RTE_EAL_IGB_UIO=n
+   CONFIG_RTE_LIBRTE_VHOST_NUMA=n CONFIG_RTE_EAL_NUMA_AWARE_HUGEPAGES=n
+
+.. note::
+
+   1. EXTRA_CFLAGS and EXTRA_LDFLAGS should be added to include the NUMA headers and link the library respectively,
+   if the step :ref:`augument_the_cross_toolcain_with_numa_support` was skipped therefore the toolchain was not
+   augumented with NUMA support.
+
+   2. RTE_DEVEL_BUILD has to be disabled, otherwise the numa.h file gets
+   a lot of compiling errors of Werror=cast-qual, Werror=strict-prototypes and Werror=old-style-definition.
+   An example is given below:
+
+   .. code-block:: console
+
+      make -j CROSS=aarch64-linux-gnu- CONFIG_RTE_KNI_KMOD=n CONFIG_RTE_EAL_IGB_UIO=n
+      RTE_DEVEL_BUILD=n EXTRA_CFLAGS="-I<numa_install_dir>/include" EXTRA_LDFLAGS=
+      "-L<numa_install_dir>/lib -lnuma"
+
diff --git a/doc/guides/linux_gsg/index.rst b/doc/guides/linux_gsg/index.rst
index 2a7bdfe..077f930 100644
--- a/doc/guides/linux_gsg/index.rst
+++ b/doc/guides/linux_gsg/index.rst
@@ -13,6 +13,7 @@ Getting Started Guide for Linux
     intro
     sys_reqs
     build_dpdk
+    cross_build_dpdk_for_arm64
     linux_drivers
     build_sample_apps
     enable_func
-- 
2.1.4