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Tue, 5 Nov 2024 18:09:43 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id KF13MGdfKmeCZwAAD6G6ig (envelope-from ); Tue, 05 Nov 2024 18:09:43 +0000 From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: Peter Xu , Peter Maydell , =?utf-8?q?Daniel_P_=2E_Berrang=C3=A9?= , =?utf-8?q?Ale?= =?utf-8?q?x_Benn=C3=A9e?= Subject: [PATCH 22/22] docs: Add migration tests documentation Date: Tue, 5 Nov 2024 15:08:37 -0300 Message-Id: <20241105180837.5990-23-farosas@suse.de> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20241105180837.5990-1-farosas@suse.de> References: <20241105180837.5990-1-farosas@suse.de> MIME-Version: 1.0 X-Spam-Score: -2.80 X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; R_RATELIMIT(0.00)[to_ip_from(RL17uas3ff86ioo43146mh3mef)]; ARC_NA(0.00)[]; TO_DN_SOME(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_FIVE(0.00)[5]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,suse.de:email]; RCVD_TLS_ALL(0.00)[] Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:2; envelope-from=farosas@suse.de; helo=smtp-out2.suse.de X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Add documentation about how to write, run and debug migration tests. Signed-off-by: Fabiano Rosas --- docs/devel/testing/index.rst | 1 + docs/devel/testing/main.rst | 13 ++ docs/devel/testing/migration.rst | 261 +++++++++++++++++++++++++++++++ docs/devel/testing/qtest.rst | 1 + 4 files changed, 276 insertions(+) create mode 100644 docs/devel/testing/migration.rst diff --git a/docs/devel/testing/index.rst b/docs/devel/testing/index.rst index 1171f7db8f..32948a9889 100644 --- a/docs/devel/testing/index.rst +++ b/docs/devel/testing/index.rst @@ -9,6 +9,7 @@ testing infrastructure. main qtest + migration functional avocado acpi-bits diff --git a/docs/devel/testing/main.rst b/docs/devel/testing/main.rst index 91f4dc61fb..fca580ae7b 100644 --- a/docs/devel/testing/main.rst +++ b/docs/devel/testing/main.rst @@ -96,6 +96,19 @@ QTest cases can be executed with make check-qtest +Migration +~~~~~~~~~ + +Migration tests are part of QTest, but are run independently. Refer +to :doc:`migration` for more details. + +Migration test cases can be executed with + +.. code:: + + make check-qtest-migration + make check-qtest--migration + Writing portable test cases ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Both unit tests and qtests can run on POSIX hosts as well as Windows hosts. diff --git a/docs/devel/testing/migration.rst b/docs/devel/testing/migration.rst new file mode 100644 index 0000000000..aa6fd65af4 --- /dev/null +++ b/docs/devel/testing/migration.rst @@ -0,0 +1,261 @@ +.. _migration: + +Migration tests +=============== + +Migration tests are part of QTest, but have some particularities of +their own, such as: + +- Extended test time due to the need to exercise the iterative phase + of migration; +- Extra requirements on the QEMU binary being used due to + :ref:`cross-version migration `; +- The use of a custom binary for the guest code to test memory + integrity (see :ref:`guest-code`). + +Invocation +---------- + +Migration tests can be ran with: + +.. code:: + + make check-qtest + make check-qtest-migration + +or directly: + +.. code:: + + # all tests + QTEST_QEMU_BINARY=./qemu-system-x86_64 ./tests/qtest/migration-test -m thorough + + # single test + QTEST_QEMU_BINARY=./qemu-system-x86_64 ./tests/qtest/migration-test -m thorough -p /x86_64/migration/bad_dest + + # all tests under /multifd (note no trailing slash) + QTEST_QEMU_BINARY=./qemu-system-x86_64 ./tests/qtest/migration-test -m thorough -r /x86_64/migration/multifd + +for cross-version tests (see :ref:`cross-version-tests`): + +.. code:: + + # old QEMU -> new QEMU + QTEST_QEMU_BINARY=./qemu-system-x86_64 QTEST_QEMU_BINARY_SRC=./old/qemu-system-x86_64 -m thorough ./tests/qtest/migration-test + QTEST_QEMU_BINARY_DST=./qemu-system-x86_64 QTEST_QEMU_BINARY=./old/qemu-system-x86_64 -m thorough ./tests/qtest/migration-test + + # new QEMU -> old QEMU (backwards migration) + QTEST_QEMU_BINARY_SRC=./qemu-system-x86_64 QTEST_QEMU_BINARY=./old/qemu-system-x86_64 -m thorough ./tests/qtest/migration-test + QTEST_QEMU_BINARY=./qemu-system-x86_64 QTEST_QEMU_BINARY_DST=./old/qemu-system-x86_64 -m thorough ./tests/qtest/migration-test + + # both _SRC and _DST variants are supported for convenience + +.. _cross-version-tests: + +Cross-version tests +~~~~~~~~~~~~~~~~~~~ + +To detect compatibility issues between different QEMU versions, all +migration tests can be executed with two different QEMU versions. The +common machine type between the two versions is used. + +To setup cross-version tests, a previous build of QEMU must be kept, +e.g.: + +.. code:: + + # build current code + mkdir build + cd build + ../configure; make + + # build previous version + cd ../ + mkdir build-9.1 + git checkout v9.1.0 + cd build + ../configure; make + +To avoid issues with newly added features and new tests, it is highly +recommended to run the tests from the source directory of *older* +version being tested. + +.. code:: + + ./build/qemu-system-x86_64 --version + QEMU emulator version 9.1.50 + + ./build-9.1/qemu-system-x86_64 --version + QEMU emulator version 9.1.0 + + cd build-9.1 + QTEST_QEMU_BINARY=./qemu-system-x86_64 QTEST_QEMU_BINARY_DST=../build/qemu-system-x86_64 ./tests/qtest/migration-test -m thorough + + +How to write migration tests +---------------------------- + +Add a test function (prefixed with ``test_``) that gets registered +with QTest using the ``migration_test_add*()`` helpers. + +.. code:: + + migration_test_add("/migration/multifd/tcp/plain/cancel", test_multifd_tcp_cancel); + +There is no formal grammar for the definition of the test paths, but +an informal rule is followed for consistency. Usually: + +``/migration////`` + +Bear in mind that the path string affects test execution order and +filtering when using the ``-r`` flag. + +For simpler tests, the test function can setup the test arguments in +the ``MigrateCommon`` structure and call into a common test +routine. Currently there are two common test routines: + + - test_precopy_common - for generic precopy migration + - test_file_common - for migration using the file: URL + +The general structure of a test routine is: + +- call ``migrate_start()`` to initialize the two QEMU + instances. Usually named "from", for the source machine and "to" for + the destination machine; + +- define the migration duration, (roughly speaking either quick or + slow) by altering the convergence parameters with + ``migrate_ensure[_non]_converge()``; + +- wait for the machines to be in the desired state with the ``wait_for_*`` + helpers; + +- migrate with ``migrate_qmp()/migrate_incoming_qmp()/migrate_qmp_fail()``; + +- check that guest memory was not corrupted and clean up the QEMU + instances with ``migrate_end()``. + +If using the common test routines, the ``.start_hook`` and +``.end_hook`` callbacks can be used to perform test-specific tasks. + +.. _guest-code: + +About guest code +---------------- + +The tests all use a custom, architecture-specific binary as the guest +code. This code, known as a-b-kernel or a-b-bootblock, constantly +iterates over the guest memory, writing a number to the start of each +guest page, incrementing it as it loops around (i.e. a generation +count). This allows the tests to catch memory corruption errors that +occur during migration as every page's first byte must have the same +value, except at the point where the transition happens. + +Whenever guest memory is migrated incorrectly, the test will output +the address and amount of pages that present a value inconsistent with +the generation count, e.g.: + +.. code:: + + Memory content inconsistency at d53000 first_byte = 27 last_byte = 26 current = 27 hit_edge = 1 + Memory content inconsistency at d54000 first_byte = 27 last_byte = 26 current = 27 hit_edge = 1 + Memory content inconsistency at d55000 first_byte = 27 last_byte = 26 current = 27 hit_edge = 1 + and in another 4929 pages + +In the scenario above, + +``first_byte`` shows that the current generation number is 27, therefore +all pages should have 27 as their first byte. Since ``hit_edge=1``, that +means the transition point was found, i.e. the guest was stopped for +migration while not all pages had yet been updated to the new +generation count. So 26 is also a valid byte to find in some pages. + +The inconsistency here is that ``last_byte``, i.e. the previous +generation count is smaller than the ``current`` byte, which should not +be possible. This would indicate a memory layout such as: + +.. code:: + + 0xb00000 | 27 00 00 ... + ... + 0xc00000 | 27 00 00 ... + ... + 0xd00000 | 27 00 00 ... + 0x?????? | 26 00 00 ... <-- pages around this addr weren't migrated correctly + ... + 0xd53000 | 27 00 00 ... + 0xd54000 | 27 00 00 ... + 0xd55000 | 27 00 00 ... + ... + +The a-b code is located at ``tests/qtest/migration/``. + +Troubleshooting +--------------- + +Migration tests usually run as part of make check, which is most +likely to not have been using the verbose flag, so the first thing to +check is the test log from meson (``meson-logs/testlog.txt``). + +There, look for the last "Running" entry, which will be the current +test. Notice whether the failing program is one of the QEMU instances +or the migration-test-* themselves. + +E.g.: + +.. code:: + + # Running /s390x/migration/precopy/unix/plain + # Using machine type: s390-ccw-virtio-9.2 + # starting QEMU: exec ./qemu-system-s390x -qtest ... + # starting QEMU: exec ./qemu-system-s390x -qtest ... + ----------------------------------- stderr ----------------------------------- + migration-test: ../tests/qtest/migration-test.c:1712: test_precopy_common: Assertion `0' failed. + + (test program exited with status code -6) + +.. code:: + + # Running /x86_64/migration/bad_dest + # Using machine type: pc-q35-9.2 + # starting QEMU: exec ./qemu-system-x86_64 -qtest ... + # starting QEMU: exec ./qemu-system-x86_64 -qtest ... + ----------------------------------- stderr ----------------------------------- + Broken pipe + ../tests/qtest/libqtest.c:205: kill_qemu() detected QEMU death from signal 6 (Aborted) (core dumped) + + (test program exited with status code -6) + +The above is usually not enough to determine what happened, so +re-running the test directly is helpful: + +.. code:: + + QTEST_QEMU_BINARY=./qemu-system-x86_64 ./tests/qtest/migration-test -m thorough -p /x86_64/migration/bad_dest + +There are also the QTEST_LOG and QTEST_TRACE variables for increased +logging and tracing. + +The QTEST_QEMU_BINARY environment variable can be abused to hook GDB +or valgrind into the invocation: + +.. code:: + + QTEST_QEMU_BINARY='gdb -q --ex "set pagination off" --ex "set print thread-events off" \ + --ex "handle SIGUSR1 noprint" --ex "break " --ex "run" --ex "quit \$_exitcode" \ + --args ./qemu-system-x86_64' ./tests/qtest/migration-test -m thorough -p /x86_64/migration/multifd/file/mapped-ram/fdset/dio + +.. code:: + + QTEST_QEMU_BINARY='valgrind -q --leak-check=full --show-leak-kinds=definite,indirect \ + ./qemu-system-x86_64' ./tests/qtest/migration-test -m thorough -r /x86_64/migration + +Whenever a test fails, it will leave behind a temporary +directory. This is useful for file migrations to inspect the generated +migration file: + +.. code:: + + $ file /tmp/migration-test-X496U2/migfile + /tmp/migration-test-X496U2/migfile: QEMU suspend to disk image + $ hexdump -C /tmp/migration-test-X496U2/migfile | less diff --git a/docs/devel/testing/qtest.rst b/docs/devel/testing/qtest.rst index c5b8546b3e..4665c160b6 100644 --- a/docs/devel/testing/qtest.rst +++ b/docs/devel/testing/qtest.rst @@ -5,6 +5,7 @@ QTest Device Emulation Testing Framework .. toctree:: qgraph + migration QTest is a device emulation testing framework. It can be very useful to test device models; it could also control certain aspects of QEMU (such as virtual