@@ -397,6 +397,119 @@ list is in the ``make docker`` help text. The frequently used ones are:
* ``DEBUG=1``: enables debug. See the previous "Debugging a Docker test
failure" section.
+Thread Sanitizer
+================
+
+Thread Sanitizer (TSan) is a tool which can detect data races. QEMU supports
+building and testing with this tool.
+
+For more information on TSan:
+
+https://github.com/google/sanitizers/wiki/ThreadSanitizerCppManual
+
+Thread Sanitizer in Docker
+---------------------------
+TSan is currently supported in the ubuntu2004 docker.
+
+Just add the TSAN=1 argument to use TSan
+
+.. code::
+
+ make docker-test-build@ubuntu2004 TSAN=1
+
+or
+
+.. code::
+
+ make docker-test-quick@ubuntu2004 TSAN=1
+
+TSan warnings under docker are placed in files located at build/tsan/.
+
+We recommend using DEBUG=1 to allow launching the test from inside the docker,
+and to allow review of the warnings generated by TSan.
+
+Building and Testing with TSan
+------------------------------
+
+It is possible to build and test with TSan, with a few additional steps.
+These steps are normally done automatically in the docker.
+
+There is a one time patch needed in clang-9 or clang-10 at this time:
+
+.. code::
+
+ sed -i 's/^const/static const/g' \
+ /usr/lib/llvm-10/lib/clang/10.0.0/include/sanitizer/tsan_interface.h
+
+To configure the build for TSan:
+
+.. code::
+
+ ../configure --enable-tsan --cc=clang-10 --cxx=clang++-10 \
+ --disable-werror --extra-cflags="-O0"
+
+The runtime behavior of TSAN is controlled by the TSAN_OPTIONS environment
+variable.
+
+More information on the TSAN_OPTIONS can be found here:
+
+https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags
+
+For example:
+
+.. code::
+
+ export TSAN_OPTIONS=suppressions=<path to qemu>/tests/tsan/suppressions.tsan \
+ detect_deadlocks=false history_size=7 exitcode=0 \
+ log_path=<build path>/tsan/tsan_warnings.txt
+
+The above exitcode=0 has TSan continue without error if any warnings are found.
+This allows for running the test and then checking the warnings afterwards.
+If you want TSan to stop and exit with error on warnings, use exitcode=66.
+
+TSan Suppressions
+-----------------
+Keep in mind that for any data race warning, although there might be a data race
+detected by TSan, there might be no actual bug here. TSan provides several
+different mechanisms for suppressing warnings. In general it is recommended
+to fix the code if possible to eliminate the data race rather than suppress
+the warning.
+
+A few important files for suppressing warnings are:
+
+tests/tsan/suppressions.tsan - Has TSan warnings we wish to suppress at runtime.
+The comment on each supression will typically indicate why we are
+suppressing it. More information on the file format can be found here:
+
+https://github.com/google/sanitizers/wiki/ThreadSanitizerSuppressions
+
+tests/tsan/blacklist.tsan - Has TSan warnings we wish to disable
+at compile time for test or debug.
+Add flags to configure to enable:
+
+"--extra-cflags=-fsanitize-blacklist=<src path>/tests/tsan/blacklist.tsan"
+
+More information on the file format can be found here under "Blacklist Format":
+
+https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags
+
+TSan Annotations
+----------------
+include/qemu/tsan.h defines annotations. See this file for more descriptions
+of the annotations themselves. Annotations can be used to suppress
+TSan warnings or give TSan more information so that it can detect proper
+relationships between accesses of data.
+
+Annotation examples can be found here:
+
+https://github.com/llvm/llvm-project/tree/master/compiler-rt/test/tsan/
+
+Good files to start with are: annotate_happens_before.cpp and ignore_race.cpp
+
+The full set of annotations can be found here:
+
+https://github.com/llvm/llvm-project/blob/master/compiler-rt/lib/tsan/rtl/tsan_interface_ann.cpp
+
VM testing
==========