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Bug#1110565: EFI runtime services not available in RT kernel

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  Bug#1110565: EFI runtime services not available in RT kernel Information BravoSystems <info@bravosystems.es> - 2025-08-08 20:10 +0200
    Bug#1110565: EFI runtime services not available in RT kernel Salvatore Bonaccorso <carnil@debian.org> - 2025-08-08 21:10 +0200
    Processed: Re: Bug#1110565: EFI runtime services not available in  RT kernel "Debian Bug Tracking System" <owner@bugs.debian.org> - 2025-08-08 21:10 +0200

#88706 — Bug#1110565: EFI runtime services not available in RT kernel

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Package: linux-image-rt-amd64
Version: 6.12.38+deb13-rt
Severity: normal

EFI runtime services are not available when booting RT kernel,
causing applications that depend on EFI variables to fail.

Steps to reproduce:
1. Boot RT kernel
2. Check: ls /sys/firmware/efi/efivars/
3. Result: Empty

Expected: EFI variables should be accessible like in non-RT kernel

Additional info:
- Non-RT kernel works fine
- CONFIG_EFIVAR_FS=m in both kernels
- CONFIG_EFI_DISABLE_RUNTIME is not set in RT kernel
- Same hardware, different behavior

When comparing

grep -E "CONFIG_EFI*" /boot/config-6.12.38+deb13-rt-amd64

against to

grep -E "CONFIG_EFI*" /boot/config-6.12.38+deb13-amd64

The result is,

debian13:~$ diff config-efi-rt.txt config-efi-no-rt.txt
21c21
< CONFIG_EFI_DISABLE_RUNTIME=y
---
> # CONFIG_EFI_DISABLE_RUNTIME is not set

Conclusion, On RT kernels seems that CONFIG_EFI_DISABLE_RUNTIME is not set.

-- System Information:
Debian 13 RC3
amd64

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#88708

Control: reassign -1 src:linux
Control: forcemerge 956752 -1

On Fri, Aug 08, 2025 at 08:05:56PM +0200, Information BravoSystems wrote:
> Package: linux-image-rt-amd64
> Version: 6.12.38+deb13-rt
> Severity: normal
> 
> EFI runtime services are not available when booting RT kernel,
> causing applications that depend on EFI variables to fail.
> 
> Steps to reproduce:
> 1. Boot RT kernel
> 2. Check: ls /sys/firmware/efi/efivars/
> 3. Result: Empty
> 
> Expected: EFI variables should be accessible like in non-RT kernel
> 
> Additional info:
> - Non-RT kernel works fine
> - CONFIG_EFIVAR_FS=m in both kernels
> - CONFIG_EFI_DISABLE_RUNTIME is not set in RT kernel
> - Same hardware, different behavior
> 
> When comparing
> 
> grep -E "CONFIG_EFI*" /boot/config-6.12.38+deb13-rt-amd64
> 
> against to
> 
> grep -E "CONFIG_EFI*" /boot/config-6.12.38+deb13-amd64
> 
> The result is,
> 
> debian13:~$ diff config-efi-rt.txt config-efi-no-rt.txt
> 21c21
> < CONFIG_EFI_DISABLE_RUNTIME=y
> ---
> > # CONFIG_EFI_DISABLE_RUNTIME is not set
> 
> Conclusion, On RT kernels seems that CONFIG_EFI_DISABLE_RUNTIME is not set.

This should be the same as #956752 . There is a documented workaround
which you can try in https://bugs.debian.org/1021245#10 .

Regards,
Salvatore

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#88710 — Processed: Re: Bug#1110565: EFI runtime services not available in RT kernel

Processing control commands:

> reassign -1 src:linux
Bug #1110565 [linux-image-rt-amd64] EFI runtime services not available in RT kernel
Bug reassigned from package 'linux-image-rt-amd64' to 'src:linux'.
No longer marked as found in versions 6.12.38+deb13-rt.
Ignoring request to alter fixed versions of bug #1110565 to the same values previously set
> forcemerge 956752 -1
Bug #956752 [src:linux] linux-image-rt-amd64: No access to EFI variables possible with rt kernels
Bug #1021245 [src:linux] linux-image-5.10.0-18-rt-amd64: can't access EFIVARS when using rt version of kernel
Bug #1089569 [src:linux] efivarfs module can't find EFI Variable Filesystem on rt kernel
Bug #1110565 [src:linux] EFI runtime services not available in RT kernel
Severity set to 'important' from 'normal'
Marked as found in versions linux/6.12.3-1, linux/4.19.98-1, linux/5.10.113-1, linux/5.16.12-1, linux/5.15.5-2, linux/5.4.19-1, and linux/5.10.140-1.
Bug #1021245 [src:linux] linux-image-5.10.0-18-rt-amd64: can't access EFIVARS when using rt version of kernel
Bug #1089569 [src:linux] efivarfs module can't find EFI Variable Filesystem on rt kernel
Merged 956752 1021245 1089569 1110565

-- 
1021245: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1021245
1089569: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1089569
1110565: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1110565
956752: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=956752
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems

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