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docs/devel/migration.rst: Format literals correctly

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In rST markup, single backticks `like this` represent "interpreted
text", which can be handled as a bunch of different things if tagged
with a specific "role":
https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#interpreted-text
(the most common one for us is "reference to a URL, which gets
hyperlinked").

The default "role" if none is specified is "title_reference",
intended for references to book or article titles, and it renders
into the HTML as <cite>...</cite> (usually comes out as italics).

To format a literal (generally rendered as fixed-width font),
double-backticks are required.

Mostly migration.rst gets this right, but some places incorrectly use
single backticks where double backticks were intended; correct them.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: 20210726142338.31872-5-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2021-07-26 15:23:32 +01:00
parent f0d7b970ac
commit 4df3a7bf8f
1 changed files with 18 additions and 18 deletions
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36
docs/devel/migration.rst
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@ -53,7 +53,7 @@ savevm/loadvm functionality.
Debugging 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: Example usage:
@ -75,8 +75,8 @@ Common infrastructure
===================== =====================
The files, sockets or fd's that carry the migration stream are abstracted by 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 the ``QEMUFile`` type (see ``migration/qemu-file.h``). In most cases this
is connected to a subtype of ``QIOChannel`` (see `io/`). is connected to a subtype of ``QIOChannel`` (see ``io/``).
Saving the state of one device 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". 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: We registered this with:
.. code:: c .. code:: c
vmstate_register(NULL, 0, &vmstate_kbd, s); 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: init function:
.. code:: c .. code:: c
@ -210,9 +210,9 @@ another to load the state back.
SaveVMHandlers *ops, SaveVMHandlers *ops,
void *opaque); void *opaque);
Two functions in the ``ops`` structure are the `save_state` Two functions in the ``ops`` structure are the ``save_state``
and `load_state` functions. Notice that `load_state` receives a version_id and ``load_state`` functions. Notice that ``load_state`` receives a version_id
parameter to know what state format is receiving. `save_state` doesn't parameter to know what state format is receiving. ``save_state`` doesn't
have a version_id parameter because it always uses the latest version. 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 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 compatibility; in general most changes can be made by adding Subsections
(see above) or _TEST macros (see above) which won't break compatibility. (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 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 the state as the newer version. But ``load_state`` sometimes is able to
load state from an older version. load state from an older version.
You can see that there are several version fields: You can see that there are several version fields:
- `version_id`: the maximum version_id supported by VMState for that device. - ``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 - ``minimum_version_id``: the minimum version_id that VMState is able to understand
for that device. 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 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 VMState is able to read versions from minimum_version_id to
version_id. And the function ``load_state_old()`` (if present) is able 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 If you use memory API functions that update memory layout outside
initialization (i.e., in response to a guest action), this is a strong 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: Examples of such memory API functions are:
- memory_region_add_subregion() - 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 processes that share memory and from QEMU. There are restrictions on the type of
memory that userfault can support shared. memory that userfault can support shared.
The Linux kernel userfault support works on `/dev/shm` memory and on `hugetlbfs` 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)` (although the kernel doesn't provide an equivalent to ``madvise(MADV_DONTNEED)``
for hugetlbfs which may be a problem in some configurations). for hugetlbfs which may be a problem in some configurations).
The vhost-user code in QEMU supports clients that have Postcopy support, 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. to support postcopy.
The client needs to open a userfaultfd and register the areas The client needs to open a userfaultfd and register the areas