Linux 6.17 EFI Stub Will Try To Maintain a Cleaner Boot Experience
The EFI code updates were merged today for the nearly-over Linux 6.17 kernel with two changes worth mentioning.
First up, the EFI pull landed the OVMF debug log driver to help with analyzing UEFI VM boot issues. Open Virtual Machine Firmware (OVMF) since edk2-stable202508 supports writing their debug log to a memory buffer. The new "ovmf-debug-log" driver in Linux 6.17 allows exposing that debug log memory buffer to Linux user-space via sysfs. Thus system administrators trying to debug QEMU+KVM boot issues can read the debug log conveniently now via /sys/firmware/efi/ovmf_debug_log.
The other change is the EFI stub "efistub" code has lowered the default log level. The commit elaborates:
With the lower default log level for the EFI stub, the hope is it will now avoid corrupting/overwriting splash screens with unimportant diagnostic outputs that aren't really useful or important for the vast majority of users. So keeping to a clean boot splash screen without any superfluous debug messages for a cleaner boot experience.
See the EFI merge for more details on these changes in Linux 6.17.
First up, the EFI pull landed the OVMF debug log driver to help with analyzing UEFI VM boot issues. Open Virtual Machine Firmware (OVMF) since edk2-stable202508 supports writing their debug log to a memory buffer. The new "ovmf-debug-log" driver in Linux 6.17 allows exposing that debug log memory buffer to Linux user-space via sysfs. Thus system administrators trying to debug QEMU+KVM boot issues can read the debug log conveniently now via /sys/firmware/efi/ovmf_debug_log.
The other change is the EFI stub "efistub" code has lowered the default log level. The commit elaborates:
"Some uefi implementations will write the efistub logs to the display over a splash image. This is not desirable for debug and info logs, so lower the default efi log level to exclude them."
With the lower default log level for the EFI stub, the hope is it will now avoid corrupting/overwriting splash screens with unimportant diagnostic outputs that aren't really useful or important for the vast majority of users. So keeping to a clean boot splash screen without any superfluous debug messages for a cleaner boot experience.
See the EFI merge for more details on these changes in Linux 6.17.