acrn-hypervisor/doc/tutorials/debug.rst
David B. Kinder 0bd384d41b doc: fix all headings to use title case
While we hoped to make the headings consistent over time while doing
other edits, we should instead just make the squirrels happy and do them
all at once or they'll likely never be made consistent.

A python script was used to find the headings, and then a call to
https://pypi.org/project/titlecase to transform the title.  A visual
inspection was used to tweak a few unexpected resulting titles.

Signed-off-by: David B. Kinder <david.b.kinder@intel.com>
2021-02-13 12:37:49 -08:00

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.. _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:`getting-started-building`
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 /tmp/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/tools/acrntrace/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/tools/acrntrace/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:`getting-started-building` 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/tools/acrntrace/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.