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| -rw-r--r-- | docs/devel/migration.rst | 36 |
1 files changed, 18 insertions, 18 deletions
diff --git a/docs/devel/migration.rst b/docs/devel/migration.rst index 19c3d4f3ea..2401253482 100644 --- a/docs/devel/migration.rst +++ b/docs/devel/migration.rst @@ -53,7 +53,7 @@ savevm/loadvm functionality. Debugging ========= -The migration stream can be analyzed thanks to `scripts/analyze-migration.py`. +The migration stream can be analyzed thanks to ``scripts/analyze-migration.py``. Example usage: @@ -75,8 +75,8 @@ Common infrastructure ===================== The files, sockets or fd's that carry the migration stream are abstracted by -the ``QEMUFile`` type (see `migration/qemu-file.h`). In most cases this -is connected to a subtype of ``QIOChannel`` (see `io/`). +the ``QEMUFile`` type (see ``migration/qemu-file.h``). In most cases this +is connected to a subtype of ``QIOChannel`` (see ``io/``). Saving the state of one device @@ -166,14 +166,14 @@ An example (from hw/input/pckbd.c) }; We are declaring the state with name "pckbd". -The `version_id` is 3, and the fields are 4 uint8_t in a KBDState structure. +The ``version_id`` is 3, and the fields are 4 uint8_t in a KBDState structure. We registered this with: .. code:: c vmstate_register(NULL, 0, &vmstate_kbd, s); -For devices that are `qdev` based, we can register the device in the class +For devices that are ``qdev`` based, we can register the device in the class init function: .. code:: c @@ -210,9 +210,9 @@ another to load the state back. SaveVMHandlers *ops, void *opaque); -Two functions in the ``ops`` structure are the `save_state` -and `load_state` functions. Notice that `load_state` receives a version_id -parameter to know what state format is receiving. `save_state` doesn't +Two functions in the ``ops`` structure are the ``save_state`` +and ``load_state`` functions. Notice that ``load_state`` receives a version_id +parameter to know what state format is receiving. ``save_state`` doesn't have a version_id parameter because it always uses the latest version. Note that because the VMState macros still save the data in a raw @@ -385,18 +385,18 @@ migration of a device, and using them breaks backward-migration compatibility; in general most changes can be made by adding Subsections (see above) or _TEST macros (see above) which won't break compatibility. -Each version is associated with a series of fields saved. The `save_state` always saves -the state as the newer version. But `load_state` sometimes is able to +Each version is associated with a series of fields saved. The ``save_state`` always saves +the state as the newer version. But ``load_state`` sometimes is able to load state from an older version. You can see that there are several version fields: -- `version_id`: the maximum version_id supported by VMState for that device. -- `minimum_version_id`: the minimum version_id that VMState is able to understand +- ``version_id``: the maximum version_id supported by VMState for that device. +- ``minimum_version_id``: the minimum version_id that VMState is able to understand for that device. -- `minimum_version_id_old`: For devices that were not able to port to vmstate, we can +- ``minimum_version_id_old``: For devices that were not able to port to vmstate, we can assign a function that knows how to read this old state. This field is - ignored if there is no `load_state_old` handler. + ignored if there is no ``load_state_old`` handler. VMState is able to read versions from minimum_version_id to version_id. And the function ``load_state_old()`` (if present) is able to @@ -454,7 +454,7 @@ data and then transferred to the main structure. If you use memory API functions that update memory layout outside initialization (i.e., in response to a guest action), this is a strong -indication that you need to call these functions in a `post_load` callback. +indication that you need to call these functions in a ``post_load`` callback. Examples of such memory API functions are: - memory_region_add_subregion() @@ -823,12 +823,12 @@ Postcopy migration with shared memory needs explicit support from the other processes that share memory and from QEMU. There are restrictions on the type of memory that userfault can support shared. -The Linux kernel userfault support works on `/dev/shm` memory and on `hugetlbfs` -(although the kernel doesn't provide an equivalent to `madvise(MADV_DONTNEED)` +The Linux kernel userfault support works on ``/dev/shm`` memory and on ``hugetlbfs`` +(although the kernel doesn't provide an equivalent to ``madvise(MADV_DONTNEED)`` for hugetlbfs which may be a problem in some configurations). The vhost-user code in QEMU supports clients that have Postcopy support, -and the `vhost-user-bridge` (in `tests/`) and the DPDK package have changes +and the ``vhost-user-bridge`` (in ``tests/``) and the DPDK package have changes to support postcopy. The client needs to open a userfaultfd and register the areas |