tree 5f193c0923b404b7fab7fd2026c3969eeb30ac44
parent 7a593ab0bb6ad33db39d49745a07b382996cc4e9
author Felix Held <felix-coreboot@felixheld.de> 1706868160 +0100
committer Felix Held <felix-coreboot@felixheld.de> 1707236922 +0000

arch/x86/ioapic: always write IOAPIC ID in set_ioapic_id

Back in the days of the APIC bus, the IOAPIC IDs mustn't overlap with
the LAPIC IDs (0 to CONFIG_MAX_CPUS - 1), but since the IOAPIC and LAPIC
nowadays talk to each other via the system bus, an IOAPIC ID of 0 is
valid. When set_ioapic_id gets called with an IOAPIC ID of 0, it skipped
writing the IOAPIC ID to the corresponding IOAPIC register, so the code
was relying of the register having the expected default value of the
IOAPIC IO 0 for things to work as expected. The case of the IOAPIC ID
being 0 is the most common case in coreboot, since that's what
register_new_ioapic_gsi0 will end up doing. Fix this issue by not making
the io_apic_write call conditional on ioapic_id being non-zero. The only
southbridge that doesn't call register_new_ioapic_gsi0, calls
set_ioapic_id with the IOAPIC ID 2 for which this won't cause any
changes in behavior.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: Ic8538f82a6b10f16eeb228669db197dc8e326ffd
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80330
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>