feat: add configurable vhost option for monitors

[vinayakjeet]

Description

This change adds a configurable vhost option to monitors.
When enabled for QEMU, it allows the use of vhost-net to improve network performance.

Related issues

• Add configurable option for vhost #410

Fixes

• Fixes Add configurable option for vhost #410

How was this tested?

• make lint
• make test_ctr

LLM usage

Yes – LLMs were used for drafting code and clarifying implementation details.
All changes were reviewed and verified manually.

Checklist

• I have read the contribution guide.
• The linter passes locally (make lint).
• The e2e tests of at least one tool pass locally (make test_ctr).
• If LLMs were used: I have read the LLM policy.

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[vinayakjeet]

This PR does not modify any files under /docs, so the MkDocs CI job was skipped as expected due to no documentation changes.

Kindly requesting a review from @cmainas and @ananos when you have time. Thank you!

[cmainas]

Hello @vinayakjeet ,

thank you for your contribution. Please fill the PR template correctly and fully. Also, please test your changes before submitting a PR.

[vinayakjeet]

@cmainas

Testing

The following tests were run locally on WSL2 (Ubuntu 24.04, amd64):

• make lint — ✅ passed

I attempted to run make test_ctr, but the tests fail in WSL due to
containerd snapshotter and mount permission limitations
(e.g. devmapper snapshotter not loaded, operation not permitted),
which require a native Linux environment with full kernel support.

All setup steps (Docker, containerd, systemd) were verified locally.
Please let CI provide the authoritative result for test_ctr.

Let me know if you would like me to re-test this on a native Linux host.

[cmainas]

Hello @vinayakjeet ,

thank you for this PR, I have added a few initial comments. However, you can at least execute the tests that do not use devmapper and specifically check if the new option in the configuration does work as expected. In the e2e test cases you can see which are the ones that do not require devmapper https://github.com/urunc-dev/urunc/blob/main/tests/e2e/test_cases.go

You can run these tests with make test_ctr_{name_of_test}, same for any other tool

[cmainas]

Thank you @vinayakjeet for the changes.

A few comments:

• vhost can be enabled for virtio block too. Therefore, the block related cli options will need to get updated too
• Would it be possibly to check the value of vhost in more unit tests. The ones that check qemu, so we can also verify the default value.

[vinayakjeet]

@cmainas - Regarding vhost for block devices:
Which approach should I use?

1. vhost-blk-pci device , swap like network,
2. vhost-user-blk , backend socket setting might be require here
3. io_uring backend

also should this use the same vhost boolean flag to control both network and block devices?

[cmainas]

Hello @vinayakjeet ,

for the time being, vhost-blk-pci would be enough. We can later make the configuration more verbose.
Also yes, the same boolean flag can be used for both network and block.

[vinayakjeet]

@cmainas can you please review the changes, thanks.

[cmainas]

Hello @vinayakjeet ,

first of all, I apologize because I did not pay enough attention to the virtio block vhost. Unfortunately, there is a need for a helper program running alongside the monitor for vhost and block. Therefore, more changes are required which can be done in the future. We can keep the network part in this PR.

Moreover, I have added a few comments about the testing. Overall the qemu_test.go does not seem to test the code in qemu.go, but in vmm.go. Also, the tests in urunc config are fine, except the last one, which can be simplified and moved to TestUruncConfigMap

[vinayakjeet]

hi @cmainas can you please review the changes. Thanks

[cmainas]

Hello @vinayakjeet ,

the changes look ok. However, in the current form the unit tests in the hypervisor package will not be executed in CI or locally. Therefore, would it be possible to add a new target in the Makefile (see test_metrics for example https://github.com/urunc-dev/urunc/blob/main/Makefile#L234)

Also, please make sure to rebase over the main branch.

[vinayakjeet]

@cmainas can you please review the changes.Thanks

[cmainas]

Thank you @vinayakjeet .

The changes look good, Please rebase over main to resolve the conflicts, so we can merge it.

[vinayakjeet]

Hi @cmainas
Rebased — could you please review it. Thanks

[cmainas]

Hello @vinayakjeet , could you also please squash your commits?

[vinayakjeet]

hi @cmainas ,commits are squashed. Thanks

[cmainas]

Thank you @vinayakjeet for this addition.