What is EFI_ALREADY_STARTED?

Quick note explaining EFI_ALREADY_STARTED for BIOS/UEFI and embedded firmware readers.

October 8, 2023 2 min read

EFI_ALREADY_STARTED is a firmware-debugging concept used to understand return status, logs, commands, or failure points.

Why it matters

Makes UEFI return values easier to interpret.
Helps write safer error handling in drivers and applications.
Useful when following service-call failures in debug logs.

Practical example

Example: do not use output parameters after a UEFI API returns an error. Check EFI_STATUS first, then decide whether to retry, allocate a larger buffer, or fail cleanly.

Quick checklist

What API returned this status?
Are input parameters, buffer size, and phase valid?
Should the caller retry, allocate more memory, or fail cleanly?

Quick takeaway

EFI_ALREADY_STARTED is a small concept, but it often becomes important when reading logs or debugging real firmware.

How I usually read it

I try not to treat EFI_ALREADY_STARTED as a dictionary entry. I read it as part of a firmware path: who produces it, who consumes it, and what symptom appears when it is wrong. That habit makes the note useful during debugging, not only during study.

Where it shows up

In real debugging, more logs do not automatically mean more clarity. I usually mark the last confirmed-good point first, then move forward one boundary at a time. EFI_ALREADY_STARTED is useful when it helps identify that boundary in the log or shell output.

In a real debugging session

EFI_ALREADY_STARTED is most useful when treated as a checkpoint in the log. Instead of asking only what it means, ask what condition creates it, which module returns it, and whether the firmware retries, falls back, or stops after it.

A small log at the right boundary is often better than noisy logs everywhere. Log the input, state before the API call, return status, and the branch taken afterward.

Public references

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