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authorThomas Gleixner <tglx@linutronix.de>2024-07-28 13:06:10 +0200
committerThomas Gleixner <tglx@linutronix.de>2024-08-09 14:34:16 +0200
commit838ba7733e4e3a94a928e8d0a058de1811a58621 (patch)
tree79a8ab458ac7bd3759904404735c7a28f39ca1a0 /arch/x86/purgatory
parent00e5bd44389145cd2f42be8e98cadb210731e72a (diff)
x86/apic: Remove logical destination mode for 64-bit
Logical destination mode of the local APIC is used for systems with up to 8 CPUs. It has an advantage over physical destination mode as it allows to target multiple CPUs at once with IPIs. That advantage was definitely worth it when systems with up to 8 CPUs were state of the art for servers and workstations, but that's history. Aside of that there are systems which fail to work with logical destination mode as the ACPI/DMI quirks show and there are AMD Zen1 systems out there which fail when interrupt remapping is enabled as reported by Rob and Christian. The latter problem can be cured by firmware updates, but not all OEMs distribute the required changes. Physical destination mode is guaranteed to work because it is the only way to get a CPU up and running via the INIT/INIT/STARTUP sequence. As the number of CPUs keeps increasing, logical destination mode becomes a less used code path so there is no real good reason to keep it around. Therefore remove logical destination mode support for 64-bit and default to physical destination mode. Reported-by: Rob Newcater <rob@durendal.co.uk> Reported-by: Christian Heusel <christian@heusel.eu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Borislav Petkov (AMD) <bp@alien8.de> Tested-by: Rob Newcater <rob@durendal.co.uk> Link: https://lore.kernel.org/all/877cd5u671.ffs@tglx
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