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phi-nguyendp · 2026-04-25T08:01:57Z

This extends migration to support paused VMs, preserving the paused state on the destination.

Changes:

Add CompletePaused protocol command that finalizes migration without resuming the VM on the destination
Skip the pause step during migration if the VM is already paused
On migration failure, only restore the running state if the VM was originally running (not paused)

Closes #7815.

phip1611

Thanks for your contribution!

Using a dedicated Migration Protocol command to decide whether the VM should be resumed on the destination is a neat and simple solution to the underlying problem. That said, I have a couple of questions and requests.

Could you please elaborate on your use case and motivation for migrating paused VMs? I’m slightly concerned that this change may be AI-assisted without being grounded in active work on live migration. Apologies if that assumption is wrong. Given the times we live in, reviewers need to be more aware and cautious about this. If you used AI/LLMs while preparing this contribution, please make sure you follow our CONTRIBUTING.md guidelines.

Also, a change like this needs integration test coverage. Please add an integration test for it. I think you can extend the existing migration helper with a paused: bool flag.

PS: Converted to draft as non-trivial parts (such as an integration tests) are missing.

phip1611 · 2026-04-27T06:26:37Z

You will need to update the mermaid diagram please:

phip1611 · 2026-04-27T06:28:00Z

@@ -979,11 +979,16 @@ impl Vmm {
            StateReceived {
                state_receive_begin,
            } => match req.command() {
-                Command::Complete => {
+                cmd @ (Command::Complete | Command::CompletePaused) => {


this combined match arm doesn't make sense! For example, we still log Migration (incoming): resume:{}ms when we do not resume the VM.

That's right, I separated them into two different arms

phi-nguyendp · 2026-04-28T13:40:18Z

Thanks for your contribution!

Using a dedicated Migration Protocol command to decide whether the VM should be resumed on the destination is a neat and simple solution to the underlying problem. That said, I have a couple of questions and requests.

Could you please elaborate on your use case and motivation for migrating paused VMs? I’m slightly concerned that this change may be AI-assisted without being grounded in active work on live migration. Apologies if that assumption is wrong. Given the times we live in, reviewers need to be more aware and cautious about this. If you used AI/LLMs while preparing this contribution, please make sure you follow our CONTRIBUTING.md guidelines.

No, I didn't use AI to write this code, although I used AI to write the commit message (not a native speaker).
When we do host maintenance, we don't want to reach out to each VM owner and ask them if we can resume/destroy their VMs before migrating them to another host. We did use the same approach for our QEMU VMs.
Real use case for cloud-hypervisor: not really, we do not have many cloud-hypervisor VMs yet.
My company started using cloud-hypervisor recently, so I want to explore how the migration feature in cloud-hypervisor works. I see this issue when reading code, and I guess it is not complicated, so I'm giving it a try.

Also, a change like this needs integration test coverage. Please add an integration test for it. I think you can extend the existing migration helper with a paused: bool flag.

I'll try to add it

PS: Converted to draft as non-trivial parts (such as an integration tests) are missing.

phip1611 · 2026-04-28T13:46:26Z

Perfect - thanks! :)

phi-nguyendp · 2026-05-01T07:46:41Z

Added integration tests

rbradford

Some tests also got accidentally deleted

rbradford · 2026-05-01T13:44:15Z

@@ -103,6 +103,7 @@ use crate::bitpos_iterator::BitposIteratorExt;
 ///     Configured --> Configured: Memory
 ///     Configured --> StateReceived: State
 ///     StateReceived --> Completed: Complete
+///     StateReceived --> PausedVMCompleted: CompletePaused


I don't see PausedVMCompleted mentioned anywhere else?

I misunderstood how the diagram was constructed, so I’ve updated it again.

rbradford · 2026-05-01T13:45:52Z

    }

    #[test]
    #[ignore = "See #5532"]
    #[cfg(target_arch = "x86_64")]
    #[cfg(not(feature = "mshv"))]
    fn test_live_upgrade_ovs_dpdk_local() {
-        _test_live_migration_ovs_dpdk(true, true);
+        _test_live_migration_ovs_dpdk(true, true, true);


Did you intend to turn it on for paused here?

I've removed this test case.

rbradford · 2026-05-01T13:49:13Z

    }

    #[test]
    #[cfg(not(feature = "mshv"))]
    fn test_live_upgrade_watchdog_local() {
-        _test_live_migration_watchdog(true, true);
+        _test_live_migration_watchdog(true, true, false);


I don't think we need all these variants.

Just one live migration and one live upgrade test with paused should be sufficient. This will consume too much CI time.

I’ve uploaded a new version. There will only be two test cases for live migration—one basic case and one local variant. For live update, since the integration tests rely on the released cloud-hypervisor-static binary, I assume I can only add new tests once scripts/run_integration_tests_x86_64.sh is updated to the new version.

phip1611 · 2026-05-04T04:17:58Z

Will review it this week.

phip1611

Thanks, LGTM! We don't do merge main into feature branch-style git histories. Instead, we use rebases. Although I think the MQ would resolve this automatically, please adapt your branch.

This extends migration to also support paused VMs, preserving the paused state on the destination. Changes: - Add CompletePaused protocol command that finalizes migration without resuming the VM on the destination - Skip the pause step during migration if the VM is already paused - On migration failure, only restore the running state if the VM was originally running (not paused) Signed-off-by: Nguyen Dinh Phi <[email protected]>

Adding a paused flag to live_migration() tests; when this flag is set, the VM will be paused before migration is performed. Signed-off-by: Nguyen Dinh Phi <[email protected]>

phi-nguyendp · 2026-05-04T08:52:15Z

Thanks, LGTM! We don't do merge main into feature branch-style git histories. Instead, we use rebases. Although I think the MQ would resolve this automatically, please adapt your branch.

I've rebased it.

phip1611 · 2026-05-04T09:14:04Z

thanks! Test coverage is looking solid. Happy to have this in the Merge Queue soon

phi-nguyendp requested a review from a team as a code owner April 25, 2026 08:01

phi-nguyendp force-pushed the phi.nguyendp/migrate-paused-vm branch 2 times, most recently from 383ed1e to a9e69d3 Compare April 25, 2026 11:11

phip1611 self-requested a review April 25, 2026 11:57

phip1611 linked an issue Apr 25, 2026 that may be closed by this pull request

migration: add support for migrating paused VMs #7815

Closed

phip1611 requested changes Apr 27, 2026

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phip1611 marked this pull request as draft April 27, 2026 08:32

phi-nguyendp force-pushed the phi.nguyendp/migrate-paused-vm branch 3 times, most recently from 72d11d7 to 39e180b Compare May 1, 2026 01:23

rbradford force-pushed the phi.nguyendp/migrate-paused-vm branch from 6b765ba to f0245b3 Compare May 1, 2026 13:38

rbradford requested changes May 1, 2026

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phi-nguyendp force-pushed the phi.nguyendp/migrate-paused-vm branch from f0245b3 to 155346a Compare May 2, 2026 05:25

rbradford approved these changes May 3, 2026

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phi-nguyendp marked this pull request as ready for review May 4, 2026 02:23

phip1611 approved these changes May 4, 2026

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phi-nguyendp added 2 commits May 4, 2026 15:35

tests: Adding integration tests for migration of paused VM

c29900e

Adding a paused flag to live_migration() tests; when this flag is set, the VM will be paused before migration is performed. Signed-off-by: Nguyen Dinh Phi <[email protected]>

phi-nguyendp force-pushed the phi.nguyendp/migrate-paused-vm branch from 622d34b to c29900e Compare May 4, 2026 07:35

rbradford approved these changes May 4, 2026

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rbradford added this pull request to the merge queue May 4, 2026

Merged via the queue into cloud-hypervisor:main with commit c595125 May 4, 2026
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likebreath added this to Cloud Hypervisor Roadmap May 14, 2026

github-project-automation Bot moved this from 🆕 New to ✅ Done in Cloud Hypervisor Roadmap May 14, 2026

github-project-automation Bot moved this to 🆕 New in Cloud Hypervisor Roadmap May 14, 2026

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phi-nguyendp commented Apr 25, 2026 • edited by phip1611 Loading Uh oh! There was an error while loading. Please reload this page.

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phi-nguyendp commented Apr 25, 2026 •

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