From: Dexuan Cui <decui@microsoft.com>
Date: Tue, 1 Dec 2020 16:45:10 -0800
Subject: iommu/hyper-v: Remove I/O-APIC ID check from
 hyperv_irq_remapping_select()
Git-commit: 26ab12bb9d96133b7880141d68b5e01a8783de9d
Patch-mainline: v5.11-rc1
References: jsc#SLE-16823

commit a491bb19f728 ("iommu/hyper-v: Implement select() method on remapping
irqdomain") restricted the irq_domain_ops::select() callback to match on
I/O-APIC index 0, which was correct until the parameter was changed to
carry the I/O APIC ID in commit f36a74b9345a.

If the ID is not 0 then the match fails. Therefore I/O-APIC init fails to
retrieve the parent irqdomain for the I/O-APIC resulting in a boot panic:

    kernel BUG at arch/x86/kernel/apic/io_apic.c:2408!

Fix it by matching the I/O-APIC independent of the ID as there is only one
I/O APIC emulated by Hyper-V.

[ tglx: Amended changelog ]

Fixes: f36a74b9345a ("x86/ioapic: Use I/O-APIC ID for finding irqdomain, not index")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/20201202004510.1818-1-decui@microsoft.com
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/iommu/hyperv-iommu.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/iommu/hyperv-iommu.c
+++ b/drivers/iommu/hyperv-iommu.c
@@ -105,8 +105,8 @@ static int hyperv_irq_remapping_select(s
 				       struct irq_fwspec *fwspec,
 				       enum irq_domain_bus_token bus_token)
 {
-	/* Claim only the first (and only) I/OAPIC */
-	return x86_fwspec_is_ioapic(fwspec) && fwspec->param[0] == 0;
+	/* Claim the only I/O APIC emulated by Hyper-V */
+	return x86_fwspec_is_ioapic(fwspec);
 }
 
 static const struct irq_domain_ops hyperv_ir_domain_ops = {