[v3,00/22] qga: clean up command source locations and conditionals

Message

Daniel P. Berrangé July 12, 2024, 1:24 p.m. UTC

This series is a side effect of other work I started, to attempt to
make the QGA safe to use in confidential VMs by automatically
restricting the permitted commands. Since this cleanup stands on
its own, I'm sending it now.

The QGA codebase has a very complicated maze of #ifdefs to create
stubs for the various commands that cannot be implemented on certain
platforms. It then has further logic to dynamically disable the stub
commands at runtime, except this is not consistently applied, so
some commands remain enabled despite being merely stubs.

The resulting code is hard to follow, when trying to understand exactly
what commands are available under what circumstances, and when changing
impls it is easy to get the #ifdefs wrong, resulting in stubs getting
missed on platforms without a real impl. In some cases, we have multiple
stubs for the same command, due to the maze of #ifdefs.

The QAPI schema language has support for many years for expressing
conditions against commands when declaring them. This results in the
QAPI code generator omitting their implementation entirely at build
time. This has mutliple benefits

 * The unsupported commands are guaranteed to not exist at runtime
 * No stubs need ever be defined in the code
 * The generated QAPI reference manual documents the build conditions

This series is broadly split into three parts

 * Moving tonnes of Linux only commands out of commands-posix.c
   into commands-linux.c to remove many #ifdefs.
 * Adding 'if' conditions in the QAPI schema to reflect the
   build conditions, removing many more #ifdefs
 * Sanitizing the logic for disabling/enabling commands at
   runtime to guarantee consistency

Changed in v3:

 - Fix missing --help output for new -c / --config arg
 - Fix typos
 - Avoid repeated qmp_command_is_enabled call

Changed in v2:

 - Make FSFreeze error reporting distinguish inability to enable
   VSS from user config choice

 - Fully remove ga_command_init_blockedrpcs() methods. No more
   special case disabling of commands. Either they're disabled
   at build time, or disabled by user config, or by well defined
   rule ie not permitted during FS freeze.

 - Apply rules later in startup to avoid crash from NULL config
   pointer

 - Document changed error messages in commit messages

 - Add -c / --config command line parameter

 - Fix mistaken enabling of fsfreeze hooks on win32

Daniel P. Berrangé (22):
  qga: drop blocking of guest-get-memory-block-size command
  qga: move linux vcpu command impls to commands-linux.c
  qga: move linux suspend command impls to commands-linux.c
  qga: move linux fs/disk command impls to commands-linux.c
  qga: move linux disk/cpu stats command impls to commands-linux.c
  qga: move linux memory block command impls to commands-linux.c
  qga: move CONFIG_FSFREEZE/TRIM to be meson defined options
  qga: conditionalize schema for commands unsupported on Windows
  qga: conditionalize schema for commands unsupported on non-Linux POSIX
  qga: conditionalize schema for commands requiring getifaddrs
  qga: conditionalize schema for commands requiring linux/win32
  qga: conditionalize schema for commands only supported on Windows
  qga: conditionalize schema for commands requiring fsfreeze
  qga: conditionalize schema for commands requiring fstrim
  qga: conditionalize schema for commands requiring libudev
  qga: conditionalize schema for commands requiring utmpx
  qga: conditionalize schema for commands not supported on other UNIX
  qga: don't disable fsfreeze commands if vss_init fails
  qga: move declare of QGAConfig struct to top of file
  qga: remove pointless 'blockrpcs_key' variable
  qga: allow configuration file path via the cli
  qga: centralize logic for disabling/enabling commands

 docs/interop/qemu-ga.rst |   19 +
 meson.build              |   16 +
 qga/commands-bsd.c       |   24 -
 qga/commands-common.h    |    9 -
 qga/commands-linux.c     | 1805 +++++++++++++++++++++++++++++
 qga/commands-posix.c     | 2373 +++-----------------------------------
 qga/commands-win32.c     |   78 +-
 qga/main.c               |  224 ++--
 qga/qapi-schema.json     |  153 ++-
 9 files changed, 2240 insertions(+), 2461 deletions(-)