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| author | Mateusz Jończyk <mat.jonczyk@o2.pl> | 2022-11-29 22:50:08 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2022-12-02 14:28:52 +0100 |
| commit | e3998434da4f5b1f57f8d6a8a9f8502ee3723bae (patch) | |
| tree | 97acbd99b74a68cd72adb25ae0dc1183ed5e97df /arch/x86/Kconfig | |
| parent | Linux 6.1-rc7 (diff) | |
| download | linux-e3998434da4f5b1f57f8d6a8a9f8502ee3723bae.tar.xz linux-e3998434da4f5b1f57f8d6a8a9f8502ee3723bae.zip | |
x86/apic: Handle no CONFIG_X86_X2APIC on systems with x2APIC enabled by BIOS
A kernel that was compiled without CONFIG_X86_X2APIC was unable to boot on
platforms that have x2APIC already enabled in the BIOS before starting the
kernel.
The kernel was supposed to panic with an approprite error message in
validate_x2apic() due to the missing X2APIC support.
However, validate_x2apic() was run too late in the boot cycle, and the
kernel tried to initialize the APIC nonetheless. This resulted in an
earlier panic in setup_local_APIC() because the APIC was not registered.
In my experiments, a panic message in setup_local_APIC() was not visible
in the graphical console, which resulted in a hang with no indication
what has gone wrong.
Instead of calling panic(), disable the APIC, which results in a somewhat
working system with the PIC only (and no SMP). This way the user is able to
diagnose the problem more easily.
Disabling X2APIC mode is not an option because it's impossible on systems
with locked x2APIC.
The proper place to disable the APIC in this case is in check_x2apic(),
which is called early from setup_arch(). Doing this in
__apic_intr_mode_select() is too late.
Make check_x2apic() unconditionally available and remove the empty stub.
Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reported-by: Robert Elliott (Servers) <elliott@hpe.com>
Signed-off-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/lkml/d573ba1c-0dc4-3016-712a-cc23a8a33d42@molgen.mpg.de
Link: https://lore.kernel.org/lkml/20220911084711.13694-3-mat.jonczyk@o2.pl
Link: https://lore.kernel.org/all/20221129215008.7247-1-mat.jonczyk@o2.pl
Diffstat (limited to 'arch/x86/Kconfig')
| -rw-r--r-- | arch/x86/Kconfig | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 67745ceab0db..b2c0fce3f257 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -462,8 +462,8 @@ config X86_X2APIC Some Intel systems circa 2022 and later are locked into x2APIC mode and can not fall back to the legacy APIC modes if SGX or TDX are - enabled in the BIOS. They will be unable to boot without enabling - this option. + enabled in the BIOS. They will boot with very reduced functionality + without enabling this option. If you don't know what to do here, say N. |