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-rw-r--r--src/arch/x86/lib/ioapic.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/src/arch/x86/lib/ioapic.c b/src/arch/x86/lib/ioapic.c
index 57b99e283e..018a42c173 100644
--- a/src/arch/x86/lib/ioapic.c
+++ b/src/arch/x86/lib/ioapic.c
@@ -85,8 +85,11 @@ void setup_ioapic(u32 ioapic_base, u8 ioapic_id)
/* Read the available number of interrupts. */
ioapic_interrupts = (io_apic_read(ioapic_base, 0x01) >> 16) & 0xff;
- if (!ioapic_interrupts || ioapic_interrupts == 0xff)
- ioapic_interrupts = 24;
+ if (ioapic_interrupts == 0xff)
+ ioapic_interrupts = 23;
+ ioapic_interrupts += 1; /* Bits 23-16 specify the maximum redirection
+ entry, which is the number of interrupts
+ minus 1. */
printk(BIOS_DEBUG, "IOAPIC: %d interrupts\n", ioapic_interrupts);
#if CONFIG_IOAPIC_INTERRUPTS_ON_FSB