x86/topology: Handle the !APIC case gracefully

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If there is no local APIC enumerated and registered then the topology
bitmaps are empty. Therefore, topology_init_possible_cpus() will die with
a division by zero exception.

Prevent this by registering a fake APIC id to populate the topology
bitmap. This also allows to use all topology query interfaces
unconditionally. It does not affect the actual APIC code because either
the local APIC address was not registered or no local APIC could be
detected.

Fixes: f1f758a805 ("x86/topology: Add a mechanism to track topology via APIC IDs")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20240322185305.242709302@linutronix.de

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Thomas Gleixner 2024-03-22 19:56:38 +01:00 • committed by Borislav Petkov (AMD)

parent 7af541cee1

commit 5e25eb25da

1 changed files with 11 additions and 0 deletions

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arch/x86/kernel/cpu/topology.c

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