This patch extends the inventory image with a `plugins` field that
contains an array of plugins which were used during checkpoint,
for example, to save GPU state. In particular, the CUDA and AMDGPU
plugins are added to this field only when the checkpoint contains
GPU state. This allows to disable unnecessary plugins during restore,
show appropriate error messages if required CRIU plugin are missing,
and migrate a process that does not use GPU from a GPU-enabled system
to CPU-only environment.
We use the `optional plugins_entry` for backwards compatibility. This
entry allows us to distinguish between *unset* and *missing* field:
- When the field is missing, it indicates that the checkpoint was
created with a previous version of CRIU, and all plugins should be
*enabled* during restore.
- When the field is empty, it indicates that no plugins were used during
checkpointing. Thus, all plugins can be *disabled* during restore.
Signed-off-by: Radostin Stoyanov <rstoyanov@fedoraproject.org>
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