linux-kernel - [PATCH] x86/ioapic: Use I/OAPIC ID for finding irqdomain, not index

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Date:   Tue, 03 Nov 2020 16:36:22 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>, lkp <oliver.sang@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        lkp@...ts.01.org, lkp@...el.com
Subject: [PATCH] x86/ioapic: Use I/OAPIC ID for finding irqdomain, not index

From: David Woodhouse <dwmw@...zon.co.uk>

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 <oliver.sang@...el.com>
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
---

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


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