nvme_driver: add admin pending command tracing

[gurasinghMS]

Adds some tracing only for pending commands on the admin queue and how long we have waited for them at the time of save.

[Copilot]

Pull request overview

Adds diagnostic tracing to the NVMe driver to help understand when admin-queue commands are still pending at save time (and for how long), plus a small test failure-message cleanup.

Changes:

• Track an issued_at timestamp for pending admin-queue commands.
• Emit tracing events for pending admin commands during QueueHandler::save().
• Update a vmm_test assertion message to avoid hard-coding a specific timeout value.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
vmm_tests/vmm_tests/tests/tests/multiarch/openhcl_servicing.rs	Updates an assertion message to reference the configured timeout rather than a specific duration.
vm/devices/storage/disk_nvme/nvme_driver/src/queue_pair.rs	Adds per-command timing for admin-queue pending commands and attempts to log pending durations at save time.

[alandau]

A few small comments, the main one being about the eager evaluation.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

[Copilot]

The elapsed field actually stores a submission timestamp (Instant), not an elapsed duration. This is confusing (especially with the inspect formatter computing elapsed() on it). Consider renaming the field to something like submitted_at/submitted_instant (or similar) and update the logging/inspect label accordingly so the name matches the stored value.

Suggested change

	#[inspect(with = "|x| x.map(|elapsed| elapsed.elapsed().as_secs_f64())")]
	elapsed: Option<Instant>,
	#[inspect(with = "|x| x.map(|instant| instant.elapsed().as_secs_f64())")]
	submitted_at: Option<Instant>,

[gurasinghMS]

@alandau on the topic of naming here: naming it "submitted_at" but having inspect log the elapsed time doesn't make much sense. What do you think?

[alandau]

We can call the field submitted_at, and rename the field only for inspect: #inspect[with = "....", rename = "elapsed"]. Good idea on printing elapsed rather than the instant.
BTW, I'm wary of using floats for time sensitive things (which might not be the case here, since we're doing this only for admin commands, but still). We can do e.g. .as_millis() as u64. A u64 millis should last for a bazillion years. Up to you.

[github-actions]

At least one Petri test failed.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

[alandau]

Looks good, thanks