From: David Woodhouse In commit b643128b917 ("x86/ioapic: Use irq_find_matching_fwspec() to find remapping irqdomain") the I/OAPIC code was changed to find its parent irqdomain using irq_find_matching_fwspec(), but the key used for the lookup was wrong. It shouldn't use 'ioapic' which is the index into its own ioapics[] array. It should use the actual arbitration ID of the I/OAPIC in question, which is mpc_ioapic_id(ioapic). Fixes: b643128b917 ("x86/ioapic: Use irq_find_matching_fwspec() to find remapping irqdomain") Reported-by: lkp Signed-off-by: David Woodhouse --- The X2APIC_OPT_OUT bit was a red herring. Once I spotted and set up a repro case such that mpc_ioapic_id(N) != N I can see it here. arch/x86/kernel/apic/io_apic.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index 443d2c9086b9..0d68e7c286e2 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -2335,14 +2335,14 @@ static int mp_irqdomain_create(int ioapic) if (cfg->dev) { fn = of_node_to_fwnode(cfg->dev); } else { - fn = irq_domain_alloc_named_id_fwnode("IO-APIC", ioapic); + fn = irq_domain_alloc_named_id_fwnode("IO-APIC", mpc_ioapic_id(ioapic)); if (!fn) return -ENOMEM; } fwspec.fwnode = fn; fwspec.param_count = 1; - fwspec.param[0] = ioapic; + fwspec.param[0] = mpc_ioapic_id(ioapic); parent = irq_find_matching_fwspec(&fwspec, DOMAIN_BUS_ANY); if (!parent) { -- 2.17.1