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The example sets its own boot_args, which replace Firecracker's default kernel command line whole, including i8042.noaux, i8042.nomux and i8042.dumbkbd. The CI kernels the guide fetches are built with ci.config, which enables CONFIG_SERIO_I8042 and CONFIG_KEYBOARD_ATKBD, so the guest then probes the emulated i8042 for a keyboard. Nested on WSL2, with the 6.18.56 CI kernel, Firecracker v1.18.0 and a minimal root image, the guest reached /init 0.67 s after start with the guide's boot args and 0.22 s with the three parameters added (five boots each). A boot without them logged "probe of serio0 returned 0 after 513968 usecs". aarch64 has no i8042, so its branch stays as it was. Signed-off-by: Michael Kortstiege <[email protected]> Co-authored-by: Claude Opus 5.5 <[email protected]>
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Changes
The getting-started example adds
i8042.noaux i8042.nomux i8042.dumbkbdto its x86_64 boot args, with a comment on why.Reason
boot_argsreplace Firecracker's default kernel command line whole (DEFAULT_KERNEL_CMDLINE, documented indocs/kernel-policy.md), including its i8042 parameters. The CI kernels the guide downloads are built withresources/guest_configs/ci.config, which enablesCONFIG_SERIO_I8042andCONFIG_KEYBOARD_ATKBD, so with the guide's boot args the guest probes the emulated i8042 for a keyboard.Measured nested on WSL2 (Intel i7-12700H, WSL 2.7.11, kernel 6.18.33.2), with the 6.18.56 CI kernel, Firecracker v1.18.0 and a minimal root image, five boots each, uptime when
/initstarts:/initconsole=ttyS0 reboot=k panic=1)A boot without the parameters logged
probe of serio0 returned 0 after 513968 usecs.docs/api_requests/actions.mdputs the probe at "a few tens of milliseconds"; nested it took about half a second, so the effect may be smaller on bare metal, where I have not measured.aarch64 has no i8042, so its branch is unchanged.
i8042.nopnpis left out: #5074 dropped it from the default because, with ACPI, it kept Ctrl-Alt-Del from working.docs/FAQ.mdanddocs/initrd.mdshow boot args without them too; I can add them there as well if you like.License Acceptance
By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license. For more information on following Developer Certificate of Origin and signing off your commits, please check
CONTRIBUTING.md.PR Checklist
tools/devtool checkbuild --allto verify that the PR passes build checks on all supported architectures. (Documentation only; I have no Docker here to run devtool.)tools/devtool checkstyle --no-clippyto verify that the PR passes the automated style checks. (Not run, as above; the change is inside a code block.)CHANGELOG.md. (No user-facing change to Firecracker itself.)TODO. (NoTODO.)rust-vmm. (Not applicable.)Drafted with Claude Code, reviewed and submitted by me.