Bug#1089569: Adding efi=runtime to kernel command line helps, but may cause latency spikes

From	Jan Dittberner <jandd@debian.org>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#1089569: Adding efi=runtime to kernel command line helps, but may cause latency spikes
Date	2026-10-01 17:30 +0200
Message-ID	<NJqTn-2W1U-1@gated-at.bofh.it> (permalink)
References	<JRCtr-f7B8-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Cross-posted to 2 groups.

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I just found out that you can add

efi=runtime

to the kernel command line if you need efivarfs using rt kernels. It is
documented in
https://docs.kernel.org/core-api/real-time/kernel-configuration.html that
CONFIG_PREEMPT_RT also sets CONFIG_EFI_DISABLE_RUNTIME because calling into
EFI can cause significant latency spikes.


Best regards
Jan

-- 
Jan Dittberner - Debian Developer
GPG-key: 4096R/0xA73E0055558FB8DD 2009-05-10
         B2FF 1D95 CE8F 7A22 DF4C  F09B A73E 0055 558F B8DD
https://portfolio.debian.net/ - https://people.debian.org/~jandd/

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Bug#1089569: Adding efi=runtime to kernel command line helps, but may cause latency spikes Jan Dittberner <jandd@debian.org> - 2026-10-01 17:30 +0200

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