.. _acrn-debug:

ACRN Debugging Tools
####################

This document describes how to use ACRN tools to collect log
and trace data for debugging.

ACRN Console Command
********************

The ACRN console provides shell commands for a user to check system states
and environment settings. See the :ref:`acrnshell` documentation for a
full list of commands, or see a summary of available commands by using
the ``help`` command within the ACRN shell.


An Example
**********

As an example, we'll show how to obtain the interrupts of a passthrough USB device.

First, we can get the USB controller BDF number (0:15.0) through the
following command in the Service VM console::

   lspci | grep "USB controller"


.. figure:: images/debug_image19.png
   :align: center

   USB controller BDF information

Second, we use the ``pt`` command in the ACRN console, and use this BDF number
to find the interrupt vector (VEC) "0x31".

.. figure:: images/debug_image20.png
   :align: center

   USB controller interrupt information

Finally we use the ``int`` command in the ACRN console, and use this
interrupt vector to find the interrupt number (909) on CPU3.

.. figure:: images/debug_image21.png
   :align: center

   USB controller interrupt number information

ACRN Log
********

ACRN log provides a console log and a mem log for a user to analyze.
We can use console log to debug directly, while mem log is a userland tool
used to capture an ACRN hypervisor log.

Turn on the Logging Info
========================

ACRN enables a console log by default.

To enable and start the mem log::

   $ systemctl enable acrnlog
   $ systemctl start acrnlog


Set and Grab Log
================

We have six (1-6) log levels for console log and mem log. The following
functions print different levels of console log and mem log::

      pr_dbg("debug...level %d", LOG_DEBUG);       //level 6
      pr_info("info...level %d", LOG_INFO);        //level 5
      pr_warn("warn...level %d", LOG_WARNING);     //level 4
      pr_err("err...level %d", LOG_ERROR);         //level 3
      pr_acrnlog("acrnlog...level %d", LOG_ACRN);  //level 2
      pr_fatal("fatal...level %d", LOG_FATAL);     //level 1

If the built-in logging doesn't provide enough information, you can add
additional logging in functions you want to debug, using the functions
noted above.  For example, add the following code into function
``shell_cmd_help`` in the source file
``acrn-hypervisor/hypervisor/debug/shell.c``:

.. figure:: images/debug_image22.png
   :align: center

   shell_cmd_help added information

Once you have instrumented the code, you need to rebuild the hypervisor and
install it on your platform. Refer to :ref:`gsg`
for detailed instructions on how to do that.

We set console log level to 5, and mem log level to 2 through the
command::

   loglevel 5 2

Then we input ``help`` into the ACRN console (this is the command that we have
just instrumented with additional log information), and check the log as follows.

.. figure:: images/debug_image23.png
   :align: center

   console log information

Then we use the command, on the ACRN console::

   vm_console

to switch to the Service VM console. Then we use the command::

   cat /var/log/acrnlog/acrnlog_cur.0

and we will see the following log:

.. figure:: images/debug_image24.png
   :align: center

   mem log information


ACRN Trace
**********

ACRN trace is a tool running on the Service VM to capture trace
data. We can use the existing trace information to analyze, and we can
add self-defined tracing to analyze code that we care about.

Using Existing Trace Event ID to Analyze Trace
==============================================

As an example, we can use the existing vm_exit trace to analyze the
reason and times of each vm_exit after we have done some operations.

1. Run the following Service VM console command to collect
   trace data::

      # acrntrace -c

2. Check current directory, and confirm the directory contains four
   trace files::

      # ls
      0 1 2 3

3. Use the command to get a summary of vmexit::

      # acrnalyze.py -i /home/trace/acrntrace/20190219-001529/1 -o vmexit --vm_exit

   .. note:: The acrnalyze.py script is in the
      ``misc/debug_tools/acrn_trace/scripts`` folder.  The location
      of the trace files produced by ``acrntrace`` may be different in your system.

   .. figure:: images/debug_image28.png
      :align: center

      vmexit summary information

Using Self-Defined Trace Event ID to Analyze Trace
==================================================

For some undefined trace event ID, we can define it by ourselves as
shown in the following example:

1. Add the following new event ID into
   ``acrn-hypervisor/hypervisor/include/debug/trace.h``:

   .. figure:: images/debug_image25.png
      :align: center

      trace event ID

2. Add the following format to
   ``misc/debug_tools/acrn_trace/scripts/formats``:

   .. figure:: images/debug_image1.png
      :align: center

      acrntrace formatted information

   .. note::

      Formats:
        ``0x00000005``: event ID for trace test

        ``%(cpu)d``: corresponding CPU index with decimal format

        ``%(event)016x``: corresponding event id with hex format

        ``%(tsc)d``: corresponding event time stamp with decimal format

        ``%(1)08x``: corresponding first Long data in TRACE_2L

3. Add trace into function ``emulate_io`` in
   ``acrn-hypervisor/hypervisor/arch/x86/guest/io_emul.c`` that we want to
   trace for the calling times of function ``emulate_io``:

   .. figure:: images/debug_image2.png
      :align: center

      inserted trace information

4. After we have inserted the trace code addition, we need to rebuild
   the ACRN hypervisor and install it on the platform. Refer to
   :ref:`gsg` for detailed instructions on how to do that.

5. Now we can use the following command in the Service VM console
   to generate acrntrace data into the current directory::

      acrntrace -c

   .. figure:: images/debug_image3.png
      :align: center

      trace collection

6. Run the console command::

      # acrntrace_format.py \
        formats /home/trace/acrntrace/20190219-001529/1 | grep "trace test"

   .. note:: The acrnalyze.py script is in the
      ``misc/debug_tools/acrn_trace/scripts`` folder.  The location
      of the trace files produced by ``acrntrace`` may be different in your system.

   and we will get the following log:

   .. figure:: images/debug_image4.png
      :align: center

      trace collection

   .. note::
      The trace data may generate on any of the available CPUs, so
      you'll need to check which CPU number was used and specify that
      CPU to analyze its trace.
