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author | Richard Henderson <richard.henderson@linaro.org> | 2023-04-27 16:46:17 +0100 |
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committer | Richard Henderson <richard.henderson@linaro.org> | 2023-04-27 16:46:17 +0100 |
commit | cc5ee50fff9dbac0aac32cd892a7163c7babcca1 (patch) | |
tree | beec35b1dcd68057c21fce9401d66421e0004521 /docs/devel | |
parent | 1eb95e1baef852d0971a1dd62a3293cd68f1ec35 (diff) | |
parent | ef46ae67ba9a785cf0cce58b5fc5a36ed3c6c7b9 (diff) | |
download | qemu-cc5ee50fff9dbac0aac32cd892a7163c7babcca1.zip qemu-cc5ee50fff9dbac0aac32cd892a7163c7babcca1.tar.gz qemu-cc5ee50fff9dbac0aac32cd892a7163c7babcca1.tar.bz2 |
Merge tag 'pull-testing-docs-270423-1' of https://gitlab.com/stsquad/qemu into staging
Testing and documentation updates:
- bump avocado to 101.0
- use snapshots for tuxrun baseline tests
- add sbda-ref test to avocado
- avoid spurious re-configure in gitlab
- better description of blockdev options
- drop FreeBSD 12 from Cirrus CI
- fix up the ast2[56]00 tests to be more stable
- improve coverage of ppc64 tests in tuxrun baselines
- limit plugin tests to just the generic multiarch binaries
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* tag 'pull-testing-docs-270423-1' of https://gitlab.com/stsquad/qemu:
docs/style: call out the use of GUARD macros
docs/devel: mention the spacing requirement for QOM
docs/devel: make a statement about includes
docs/system: remove excessive punctuation from guest-loader docs
qemu-options.hx: Update descriptions of memory options for NUMA node
tests/tcg: limit the scope of the plugin tests
tests/avocado/tuxrun_baselines.py: improve code coverage for ppc64
avocado_qemu/__init__.py: factor out the qemu-img finding
MAINTAINERS: Cover tests/avocado/machine_aspeed.py
tests/avocado/machine_aspeed: Fix the broken ast2[56]00_evb_sdk tests
tests/avocado: Make ssh_command_output_contains() globally available
.gitlab-ci.d/cirrus: Drop the CI job for compiling with FreeBSD 12
qemu-options: finesse the recommendations around -blockdev
scripts/device-crash-test: Add a parameter to run with TCG only
gitlab-ci: Avoid to re-run "configure" in the device-crash-test jobs
tests/avocado: Add set of boot tests on SBSA-ref
tests/avocado: use the new snapshots for testing
tests/requirements.txt: bump up avocado-framework version to 101.0
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Diffstat (limited to 'docs/devel')
-rw-r--r-- | docs/devel/qom.rst | 2 | ||||
-rw-r--r-- | docs/devel/style.rst | 105 |
2 files changed, 107 insertions, 0 deletions
diff --git a/docs/devel/qom.rst b/docs/devel/qom.rst index 3e34b07..c923795 100644 --- a/docs/devel/qom.rst +++ b/docs/devel/qom.rst @@ -1,3 +1,5 @@ +.. _qom: + =========================== The QEMU Object Model (QOM) =========================== diff --git a/docs/devel/style.rst b/docs/devel/style.rst index 68aa776..aa5e083 100644 --- a/docs/devel/style.rst +++ b/docs/devel/style.rst @@ -300,6 +300,20 @@ putting those into qemu/typedefs.h instead of including the header. Cyclic inclusion is forbidden. +Generative Includes +------------------- + +QEMU makes fairly extensive use of the macro pre-processor to +instantiate multiple similar functions. While such abuse of the macro +processor isn't discouraged it can make debugging and code navigation +harder. You should consider carefully if the same effect can be +achieved by making it easy for the compiler to constant fold or using +python scripting to generate grep friendly code. + +If you do use template header files they should be named with the +``.c.inc`` or ``.h.inc`` suffix to make it clear they are being +included for expansion. + C types ======= @@ -614,6 +628,97 @@ are still some caveats to beware of QEMU Specific Idioms ******************** +QEMU Object Model Declarations +============================== + +The QEMU Object Model (QOM) provides a framework for handling objects +in the base C language. The first declaration of a storage or class +structure should always be the parent and leave a visual space between +that declaration and the new code. It is also useful to separate +backing for properties (options driven by the user) and internal state +to make navigation easier. + +For a storage structure the first declaration should always be called +"parent_obj" and for a class structure the first member should always +be called "parent_class" as below: + +.. code-block:: c + + struct MyDeviceState { + DeviceState parent_obj; + + /* Properties */ + int prop_a; + char *prop_b; + /* Other stuff */ + int internal_state; + }; + + struct MyDeviceClass { + DeviceClass parent_class; + + void (*new_fn1)(void); + bool (*new_fn2)(CPUState *); + }; + +Note that there is no need to provide typedefs for QOM structures +since these are generated automatically by the QOM declaration macros. +See :ref:`qom` for more details. + +QEMU GUARD macros +================= + +QEMU provides a number of ``_GUARD`` macros intended to make the +handling of multiple exit paths easier. For example using +``QEMU_LOCK_GUARD`` to take a lock will ensure the lock is released on +exit from the function. + +.. code-block:: c + + static int my_critical_function(SomeState *s, void *data) + { + QEMU_LOCK_GUARD(&s->lock); + do_thing1(data); + if (check_state2(data)) { + return -1; + } + do_thing3(data); + return 0; + } + +will ensure s->lock is released however the function is exited. The +equivalent code without _GUARD macro makes us to carefully put +qemu_mutex_unlock() on all exit points: + +.. code-block:: c + + static int my_critical_function(SomeState *s, void *data) + { + qemu_mutex_lock(&s->lock); + do_thing1(data); + if (check_state2(data)) { + qemu_mutex_unlock(&s->lock); + return -1; + } + do_thing3(data); + qemu_mutex_unlock(&s->lock); + return 0; + } + +There are often ``WITH_`` forms of macros which more easily wrap +around a block inside a function. + +.. code-block:: c + + WITH_RCU_READ_LOCK_GUARD() { + QTAILQ_FOREACH_RCU(kid, &bus->children, sibling) { + err = do_the_thing(kid->child); + if (err < 0) { + return err; + } + } + } + Error handling and reporting ============================ |