Add an --ondemand flag to the offload daemon's restore subcommand to
support the post-copy mechanism from the live migration protocol.
In on-demand mode, the daemon creates empty memfds to back the guest
memory and sends them over to the VMM. This lets the VM start quickly,
right after the memfds are mapped into CH's address space.
At runtime, when the guest accesses a page (or the prefault handler
requests it), the daemon faults it in by copying the page content into
its shared memory mapping, then replies to the PageFault request so the
VMM can consider the page present.
Signed-off-by: Sebastien Boeuf <sboeuf@meta.com>
Assisted-by: Claude:claude-opus-4-7
Extending the snapshot/restore documentation so that it explains what
are the goals behind this offloaded snapshot/restore feature, how to use
it in practice, and also by documenting the protocol used by the offload
daemon so that anyone could write its own daemon.
By relying on the existing local live migration support and reusing the
semantics and the protocol associated with it, we intend to provide a
way for snapshotting and restoring a VM to/from a dedicated process that
we can call the offload daemon.
By allowing an external process to perform the snapshot/restore actions
on behalf of Cloud Hypervisor, we give our users the opportunity to
implement their own offloaded daemon. The goal is to avoid bloating
Cloud Hypervisor with numerous features related to snapshot/restore, and
let the user decide how to perform the snapshot/restore actions. One
example is that we can decide to encrypt the guest RAM on the fly in
order to avoid writing an unencrypted version to local disk. Another
example is to be able to send guest RAM and associated state/config data
over the network without having to persist the data first to local
storage.
There might be other reasons to choose going with an offloaded daemon to
perform the snapshot/restore of the VM, but in every case, this empowers
the user to make their own choice.
Signed-off-by: Sebastien Boeuf <sboeuf@meta.com>
Assisted-by: Claude:claude-opus-4-7
Add an option that can be used when restoring to resume the VM. This is
particularly useful when restoring the VM via the direct VMM command
line, when you might not want/have an API socket configured.
Signed-off-by: Rob Bradford <rbradford@meta.com>
Add a MemoryRestoreMode enum (Copy | OnDemand) to RestoreConfig so
the restore path can be selected at restore time. Copy preserves the
existing eager read-copy behavior. OnDemand enables userfaultfd-based
demand paging and fails restore if the kernel does not support it.
Validate that prefault=on is not combined with OnDemand mode.
Update the OpenAPI spec with the new enum field.
Signed-off-by: Shayon Mukherjee <shayonj@gmail.com>
This commit removes the SGX support from cloud hypervisor. SGX support
was deprecated in May as part of #7090.
Signed-off-by: Shubham Chakrawar <schakrawar@crusoe.ai>
Add a section about restoring VM with new Net FDs explicitly passed to
ch-remote via 'net_fds' parameter
Signed-off-by: Purna Pavan Chandra <paekkaladevi@linux.microsoft.com>
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>
Remove the bits about this feature being experimental, as well as
limitations around virtio-mem and vhost-user devices.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The proper way to refer to the project is "Cloud Hypervisor" without the
hyphen in the middle. On the other hand, if one refers to the binary
name, it is "cloud-hypervisor".
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Add some documentation regarding the snapshot/restore feature which was
introduced earlier, explaining how the feature works and how to use it
properly.
Fixes#1490
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
