[Patch Part1 V2 09/29] x86, ACPI, irq: fix possible eror in GSI to IRQ mapping for legacy IRQ

[Jiang Liu]

A default identity mapping between GSI and IRQ is built for legacy IRQs.
So when overriding the default identity mapping for legacy IRQs,
we should also invalidate isa_irq_to_gsi[gsi] when setting
isa_irq_to_gsi[irq] = gsi.  Otherwise there may be two entries with the
same GSI in the isa_irq_to_gsi array, and acpi_isa_irq_to_gsi() may give
wrong result.

Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/acpi/boot.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 8b8ff786af12..dccf9e88db30 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -508,7 +508,8 @@ EXPORT_SYMBOL_GPL(acpi_gsi_to_irq);
 
 int acpi_isa_irq_to_gsi(unsigned isa_irq, u32 *gsi)
 {
-	if (isa_irq < NR_IRQS_LEGACY) {
+	if (isa_irq < NR_IRQS_LEGACY &&
+	    isa_irq_to_gsi[isa_irq] != ACPI_INVALID_GSI) {
 		*gsi = isa_irq_to_gsi[isa_irq];
 		return 0;
 	}
@@ -913,6 +914,13 @@ static void __init mp_override_legacy_irq(u8 bus_irq, u8 polarity, u8 trigger,
 
 	mp_save_irq(&mp_irq);
 
+	/*
+	 * Reset default identity mapping if gsi is also an legacy IRQ,
+	 * otherwise there will be more than one entry with the same GSI
+	 * and acpi_isa_irq_to_gsi() may give wrong result.
+	 */
+	if (gsi < NR_IRQS_LEGACY && isa_irq_to_gsi[gsi] == gsi)
+		isa_irq_to_gsi[gsi] = ACPI_INVALID_GSI;
 	isa_irq_to_gsi[bus_irq] = gsi;
 }
 
-- 
1.7.10.4

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