[tip: x86/apic] iommu/hyper-v: Remove I/O-APIC ID check from hyperv_irq_remapping_select()

[tip-bot2 for Dexuan Cui]

The following commit has been merged into the x86/apic branch of tip:

Commit-ID:     26ab12bb9d96133b7880141d68b5e01a8783de9d
Gitweb:        https://git.kernel.org/tip/26ab12bb9d96133b7880141d68b5e01a8783de9d
Author:        Dexuan Cui <decui@xxxxxxxxxxxxx>
AuthorDate:    Tue, 01 Dec 2020 16:45:10 -08:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Wed, 02 Dec 2020 11:22:55 +01:00

iommu/hyper-v: Remove I/O-APIC ID check from hyperv_irq_remapping_select()

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@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20201202004510.1818-1-decui@xxxxxxxxxxxxx
---
 drivers/iommu/hyperv-iommu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c
index 9438daa..1d21a0b 100644
--- a/drivers/iommu/hyperv-iommu.c
+++ b/drivers/iommu/hyperv-iommu.c
@@ -105,8 +105,8 @@ static int hyperv_irq_remapping_select(struct irq_domain *d,
 				       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 = {