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Diffstat (limited to 'src/arch/x86/ioapic.c')
-rw-r--r--src/arch/x86/ioapic.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/src/arch/x86/ioapic.c b/src/arch/x86/ioapic.c
index 84a4c7f7bc..04c852b4c2 100644
--- a/src/arch/x86/ioapic.c
+++ b/src/arch/x86/ioapic.c
@@ -147,7 +147,12 @@ static void set_ioapic_id(void *ioapic_base, u8 ioapic_id)
u8 get_ioapic_id(void *ioapic_base)
{
- return (io_apic_read(ioapic_base, 0x00) >> 24) & 0x0f;
+ /*
+ * According to 82093AA I/O ADVANCED PROGRAMMABLE INTERRUPT CONTROLLER (IOAPIC)
+ * only 4 bits (24:27) are used for the ID. In practice the upper bits are either
+ * always 0 or used for larger IDs.
+ */
+ return (io_apic_read(ioapic_base, 0x00) >> 24) & 0xff;
}
u8 get_ioapic_version(void *ioapic_base)