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vmm: Split VM config and VM state for snapshot/restore

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In order to allow for human readable output for the VM configuration, we
pull it out of the snapshot, which becomes effectively the list of
states from the VM. The configuration is stored through a dedicated file
in JSON format (not including any binary output).

Having the ability to read and modify the VM configuration manually
between the snapshot and restore phases makes debugging easier, as well
as empowers users for extending the use cases relying on the
snapshot/restore feature.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
This commit is contained in:
Sebastien Boeuf
2022-02-08 11:32:19 +01:00
committed by Rob Bradford
parent 6717ac0cf2
commit 10676b74dc
4 changed files with 79 additions and 37 deletions
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17
docs/snapshot_restore.md
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@@ -43,17 +43,22 @@ ll /home/foo/snapshot/
total 4194536
drwxrwxr-x 2 foo bar 4096 Jul 22 11:50 ./
drwxr-xr-x 47 foo bar 4096 Jul 22 11:47 ../
-rw------- 1 foo bar 1084 Jul 22 11:19 config.json
-rw------- 1 foo bar 4294967296 Jul 22 11:19 memory-ranges
-rw------- 1 foo bar 217853 Jul 22 11:19 vm.json
-rw------- 1 foo bar 217853 Jul 22 11:19 state.json
```
`config.json` contains the virtual machine configuration. It is used to create
a similar virtual machine with the correct amount of CPUs, RAM, and other
expected devices. It is stored in a human readable format so that it could be
modified between the snapshot and restore phases to achieve some very special
use cases. But for most cases, manually modifying the configuration should not
be needed.
`memory-ranges` stores the content of the guest RAM.
`vm.json` gathers all information related to the virtual machine configuration
and state. The configuration bits are used to create a similar virtual machine
with the correct amount of CPUs, RAM, and other expected devices. The state
bits are used to restore each component in the state it was left before the
snapshot occurred.
`state.json` contains the virtual machine state. It is used to restore each
component in the state it was left before the snapshot occurred.
## Restore a Cloud Hypervisor VM