1================================== 2ACPI/SMBIOS testing using biosbits 3================================== 4************ 5Introduction 6************ 7Biosbits is a software written by Josh Triplett that can be downloaded 8from https://biosbits.org/. The github codebase can be found 9`here <https://github.com/biosbits/bits/tree/master>`__. It is a software that 10executes the bios components such as acpi and smbios tables directly through 11acpica bios interpreter (a freely available C based library written by Intel, 12downloadable from https://acpica.org/ and is included with biosbits) without an 13operating system getting involved in between. Bios-bits has python integration 14with grub so actual routines that executes bios components can be written in 15python instead of bash-ish (grub's native scripting language). 16There are several advantages to directly testing the bios in a real physical 17machine or in a VM as opposed to indirectly discovering bios issues through the 18operating system (the OS). Operating systems tend to bypass bios problems and 19hide them from the end user. We have more control of what we wanted to test and 20how by being as close to the bios on a running system as possible without a 21complicated software component such as an operating system coming in between. 22Another issue is that we cannot exercise bios components such as ACPI and 23SMBIOS without being in the highest hardware privilege level, ring 0 for 24example in case of x86. Since the OS executes from ring 0 whereas normal user 25land software resides in unprivileged ring 3, operating system must be modified 26in order to write our test routines that exercise and test the bios. This is 27not possible in all cases. Lastly, test frameworks and routines are preferably 28written using a high level scripting language such as python. OSes and 29OS modules are generally written using low level languages such as C and 30low level assembly machine language. Writing test routines in a low level 31language makes things more cumbersome. These and other reasons makes using 32bios-bits very attractive for testing bioses. More details on the inspiration 33for developing biosbits and its real life uses were presented `at Plumbers 34in 2011 <Plumbers_>`__ and `at Linux.conf.au in 2012 <Linux.conf.au_>`__. 35 36For QEMU, we maintain a fork of bios bits in `gitlab`_, along with all 37the dependent submodules. This fork contains numerous fixes, a newer 38acpica and changes specific to running these functional QEMU tests using 39bits. The author of this document is the current maintainer of the QEMU 40fork of bios bits repository. For more information, please see `the 41author's FOSDEM presentation <FOSDEM_>`__ on this bios-bits based test framework. 42 43.. _Plumbers: https://blog.linuxplumbersconf.org/2011/ocw/system/presentations/867/original/bits.pdf 44.. _Linux.conf.au: https://www.youtube.com/watch?v=36QIepyUuhg 45.. _gitlab: https://gitlab.com/qemu-project/biosbits-bits 46.. _FOSDEM: https://fosdem.org/2024/schedule/event/fosdem-2024-2262-exercising-qemu-generated-acpi-smbios-tables-using-biosbits-from-within-a-guest-vm-/ 47 48********************************* 49Description of the test framework 50********************************* 51 52Under the directory ``tests/functional/``, ``test_acpi_bits.py`` is a QEMU 53functional test that drives all this. 54 55A brief description of the various test files follows. 56 57Under ``tests/functional/`` as the root we have: 58 59:: 60 61 ├── acpi-bits 62 │ ├── bits-config 63 │ │ └── bits-cfg.txt 64 │ ├── bits-tests 65 │ ├── smbios.py2 66 │ ├── testacpi.py2 67 │ └── testcpuid.py2 68 ├── test_acpi_bits.py 69 70* ``tests/functional``: 71 72 ``test_acpi_bits.py``: 73 This is the main python functional test script that generates a 74 biosbits iso. It then spawns a QEMU VM with it, collects the log and reports 75 test failures. This is the script one would be interested in if they wanted 76 to add or change some component of the log parsing, add a new command line 77 to alter how QEMU is spawned etc. Test writers typically would not need to 78 modify this script unless they wanted to enhance or change the log parsing 79 for their tests. In order to enable debugging, you can set **V=1** 80 environment variable. This enables verbose mode for the test and also dumps 81 the entire log from bios bits and more information in case failure happens. 82 You can also set **BITS_DEBUG=1** to turn on debug mode. It will enable 83 verbose logs and also retain the temporary work directory the test used for 84 you to inspect and run the specific commands manually. 85 86 In order to run this test, please perform the following steps from the QEMU 87 build directory (assuming that the sources are in ".."): 88 :: 89 90 $ export PYTHONPATH=../python:../tests/functional 91 $ export QEMU_TEST_QEMU_BINARY=$PWD/qemu-system-x86_64 92 $ python3 ../tests/functional/test_acpi_bits.py 93 94 The above will run all acpi-bits functional tests (producing output in 95 tap format). 96 97 You can inspect the log files in tests/functional/x86_64/test_acpi_bits.*/ 98 for more information about the run or in order to diagnoze issues. 99 If you pass V=1 in the environment, more diagnostic logs will be put into 100 the test log. 101 102* ``tests/functional/acpi-bits/bits-config``: 103 104 This location contains biosbits configuration files that determine how the 105 software runs the tests. 106 107 ``bits-config.txt``: 108 This is the biosbits config file that determines what tests 109 or actions are performed by bits. The description of the config options are 110 provided in the file itself. 111 112* ``tests/functional/acpi-bits/bits-tests``: 113 114 This directory contains biosbits python based tests that are run from within 115 the biosbits environment in the spawned VM. New additions of test cases can 116 be made in the appropriate test file. For example, new acpi tests can go 117 into testacpi.py2 and one would call testsuite.add_test() to register the new 118 test so that it gets executed as a part of the ACPI tests. 119 It might be occasionally necessary to disable some subtests or add a new 120 test that belongs to a test suite not already present in this directory. To 121 do this, please clone the bits source from 122 https://gitlab.com/qemu-project/biosbits-bits/-/tree/qemu-bits. 123 Note that this is the "qemu-bits" branch and not the "bits" branch of the 124 repository. "qemu-bits" is the branch where we have made all the QEMU 125 specific enhancements and we must use the source from this branch only. 126 Copy the test suite/script that needs modification (addition of new tests 127 or disabling them) from python directory into this directory. For 128 example, in order to change cpuid related tests, copy the following 129 file into this directory and rename it with .py2 extension: 130 https://gitlab.com/qemu-project/biosbits-bits/-/blob/qemu-bits/python/testcpuid.py 131 Then make your additions and changes here. Therefore, the steps are: 132 133 (a) Copy unmodified test script to this directory from bits source. 134 (b) Add a SPDX license header. 135 (c) Perform modifications to the test. 136 137 Commits (a), (b) and (c) preferably should go under separate commits so that 138 the original test script and the changes we have made are separated and 139 clear. (a) and (b) can sometimes be combined into a single step. 140 141 The test framework will then use your modified test script to run the test. 142 No further changes would be needed. Please check the logs to make sure that 143 appropriate changes have taken effect. 144 145 The tests have an extension .py2 in order to indicate that: 146 147 (a) They are python2.7 based scripts and not python 3 scripts. 148 (b) They are run from within the bios bits VM and is not subjected to QEMU 149 build/test python script maintenance and dependency resolutions. 150 (c) They need not be loaded by the test framework by accident when running 151 tests. 152 153 154Author: Ani Sinha <anisinha@redhat.com> 155 156