Added snapshot feature for vhost-device-vsock.

[WeiChungHsu]

Added snapshot feature for vhost-device-vsock. There is a hang issue during snapshot disable vring, my solution is to check vring enable/disable status but it requires a new function get_enabled from vring. The vring new function get_enabled PR is here: https://github.com/rust-vmm/vhost/pull/284

More detailed explain the hang issue: When the Vring is disabled (and queue set to not ready), the vhu_vsock_thread.rs still try to iterate and read RX queue, therefore, it hang at this line: https://github.com/rust-vmm/vhost-device/blob/main/vhost-device-vsock/src/vhu_vsock_thread.rs#L591-L594

Furthermore, it hang because this Queue iter() operation return error at this line: https://github.com/rust-vmm/vm-virtio/blob/main/virtio-queue/src/queue.rs#L592-L597

Requirements

Before submitting your PR, please make sure you addressed the following requirements:

• [ ] All commits in this PR have Signed-Off-By trailers (with git commit -s), and the commit message has max 60 characters for the summary and max 75 characters for each description line.
• [ ] All added/changed functionality has a corresponding unit/integration test.
• [ ] All added/changed public-facing functionality has entries in the "Upcoming Release" section of CHANGELOG.md (if no such section exists, please create one).
• [ ] Any newly added unsafe code is properly documented.

[stefano-garzarella]

@WeiChungHsu CI is failing, please fix it.

[stefano-garzarella]

The vring new function get_enabled PR is here: https://github.com/rust-vmm/vhost/pull/284

We can't merge code that depends on ongoing work, so I mark this as draft. Please also temporary change the vhost crate dep to a git repo that contains the change, so the CI can test this code. When the changes to vhost will be merged, we can remove that and mark this as ready.

[WeiChungHsu]

@WeiChungHsu CI is failing, please fix it.

Sorry, I am fixing and working on it now.

[WeiChungHsu]

Also, the commit message is all on one line. Please put a short descriptive commit title and use the commit message body for longer text.

Fixed the commit message with sign-off. Thanks!

[WeiChungHsu]

I fixed the most of CI failures, but the this failure is based on another PR in vhost crate: "error[E0599]: no method named get_enabled found". Therefore, I have to wait that PR merged first. The pending PR in vhost crate is: https://github.com/rust-vmm/vhost/pull/291

[stefano-garzarella]

I fixed the most of CI failures, but the this failure is based on another PR in vhost crate: "error[E0599]: no method named get_enabled found". Therefore, I have to wait that PR merged first. The pending PR in vhost crate is: rust-vmm/vhost#284

As I mentioned here https://github.com/rust-vmm/vhost-device/pull/827#issuecomment-2732414521 can you change Cargo.toml to point to your branch used for https://github.com/rust-vmm/vhost/pull/284 ?

In this way we can test also this PR. When that PR will be merged and a new vhost-user-backend released, we can remove that change and mark this PR ready to be merged.

[stefano-garzarella]

@WeiChungHsu also, instead of clicking on "Update branch", you can go to the arrow and do "Update with rebase" (maybe I should see if I can enable it by default)