docs/migration: add uadk compression feature

Document UADK(User Space Accelerator Development Kit) library details
and how to use that for migration.

Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Reviewed-by: Zhangfei Gao <zhangfei.gao@linaro.org>
[s/Qemu/QEMU in docs]
Signed-off-by: Fabiano Rosas <farosas@suse.de>

docs/devel/migration/features.rst

@@ -13,3 +13,4 @@ Migration has plenty of features to support different use cases.
    mapped-ram
    CPR
    qpl-compression
+   uadk-compression

docs/devel/migration/uadk-compression.rst

@@ -0,0 +1,144 @@
+=========================================================
+User Space Accelerator Development Kit (UADK) Compression
+=========================================================
+UADK is a general-purpose user space accelerator framework that uses shared
+virtual addressing (SVA) to provide a unified programming interface for
+hardware acceleration of cryptographic and compression algorithms.
+
+UADK includes Unified/User-space-access-intended Accelerator Framework (UACCE),
+which enables hardware accelerators from different vendors that support SVA to
+adapt to UADK.
+
+Currently, HiSilicon Kunpeng hardware accelerators have been registered with
+UACCE. Through the UADK framework, users can run cryptographic and compression
+algorithms using hardware accelerators instead of CPUs, freeing up CPU
+computing power and improving computing performance.
+
+https://github.com/Linaro/uadk/tree/master/docs
+
+UADK Framework
+==============
+UADK consists of UACCE, vendors' drivers, and an algorithm layer. UADK requires
+the hardware accelerator to support SVA, and the operating system to support
+IOMMU and SVA. Hardware accelerators from different vendors are registered as
+different character devices with UACCE by using kernel-mode drivers of the
+vendors. A user can access the hardware accelerators by performing user-mode
+operations on the character devices.
+
+::
+
+          +----------------------------------+
+          |                apps              |
+          +----+------------------------+----+
+               |                        |
+               |                        |
+       +-------+--------+       +-------+-------+
+       |   scheduler    |       | alg libraries |
+       +-------+--------+       +-------+-------+
+               |                         |
+               |                         |
+               |                         |
+               |                +--------+------+
+               |                | vendor drivers|
+               |                +-+-------------+
+               |                  |
+               |                  |
+            +--+------------------+--+
+            |         libwd          |
+    User    +----+-------------+-----+
+    --------------------------------------------------
+    Kernel    +--+-----+   +------+
+              | uacce  |   | smmu |
+              +---+----+   +------+
+                  |
+              +---+------------------+
+              | vendor kernel driver |
+              +----------------------+
+    --------------------------------------------------
+             +----------------------+
+             |   HW Accelerators    |
+             +----------------------+
+
+UADK Installation
+-----------------
+Build UADK
+^^^^^^^^^^
+
+.. code-block:: shell
+
+    git clone https://github.com/Linaro/uadk.git
+    cd uadk
+    mkdir build
+    ./autogen.sh
+    ./configure --prefix=$PWD/build
+    make
+    make install
+
+Without --prefix, UADK will be installed to /usr/local/lib by default.
+If get error:"cannot find -lnuma", please install the libnuma-dev
+
+Run pkg-config libwd to ensure env is setup correctly
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+* export PKG_CONFIG_PATH=$PWD/build/lib/pkgconfig
+* pkg-config libwd --cflags --libs
+  -I/usr/local/include -L/usr/local/lib -lwd
+
+* export PKG_CONFIG_PATH is required on demand.
+  Not required if UADK is installed to /usr/local/lib
+
+UADK Host Kernel Requirements
+-----------------------------
+User needs to make sure that ``UACCE`` is already supported in Linux kernel.
+The kernel version should be at least v5.9 with SVA (Shared Virtual
+Addressing) enabled.
+
+Kernel Configuration
+^^^^^^^^^^^^^^^^^^^^
+
+``UACCE`` could be built as module or built-in.
+
+Here's an example to enable UACCE with hardware accelerator in HiSilicon
+Kunpeng platform.
+
+*    CONFIG_IOMMU_SVA_LIB=y
+*    CONFIG_ARM_SMMU=y
+*    CONFIG_ARM_SMMU_V3=y
+*    CONFIG_ARM_SMMU_V3_SVA=y
+*    CONFIG_PCI_PASID=y
+*    CONFIG_UACCE=y
+*    CONFIG_CRYPTO_DEV_HISI_QM=y
+*    CONFIG_CRYPTO_DEV_HISI_ZIP=y
+
+Make sure all these above kernel configurations are selected.
+
+Accelerator dev node permissions
+--------------------------------
+Harware accelerators(eg: HiSilicon Kunpeng Zip accelerator) gets registered to
+UADK and char devices are created in dev directory. In order to access resources
+on hardware accelerator devices, write permission should be provided to user.
+
+.. code-block:: shell
+
+    $ sudo chmod 777 /dev/hisi_zip-*
+
+How To Use UADK Compression In QEMU Migration
+---------------------------------------------
+* Make sure UADK is installed as above
+* Build ``QEMU`` with ``--enable-uadk`` parameter
+
+  E.g. configure --target-list=aarch64-softmmu --enable-kvm ``--enable-uadk``
+
+* Enable ``UADK`` compression during migration
+
+  Set ``migrate_set_parameter multifd-compression uadk``
+
+Since UADK uses Shared Virtual Addressing(SVA) and device access virtual memory
+directly it is possible that SMMUv3 may enounter page faults while walking the
+IO page tables. This may impact the performance. In order to mitigate this,
+please make sure to specify ``-mem-prealloc`` parameter to the destination VM
+boot parameters.
+
+Though both UADK and ZLIB are based on the deflate compression algorithm, UADK
+is not fully compatible with ZLIB. Hence, please make sure to use ``uadk`` on
+both source and destination during migration.