How is the interrupt vector SCI - system management?

Question

According to the ACPI specification, the FADT table (fixed ACPI table) contains a field that tells the OS the SCI interrupt number for the OS. The field is defined as follows:

I reset the FADT table on the Intel x86 platform and saw that the SCI interrupt was due to the number 9:

But according to Intel guidelines, 0-31are reserved vectors for IA-architecturally defined interrupts. In particular, it 9is defined as:

, , 9 I386. , 9I SCI. x86- ACPI.

?

ADD 1

, - . .

Answer 1

ACPI , , (GSI).
GSI 5.2.13 " " 6.1 ACPI, ¹.

ACPI Plug and Play IRQ.
  ASL, .

GSI.
, GSI 9 9.
, , , "" "" " ", Intel.

GSI, IRQ.
x86:

• 8259A PIC ^{[datasheet] [OSDev wiki]}
  IO- PIC, (IR 0-7).
  IRQ 0-7.
  IRQ 8-15, IR2 ².

• IO APIC ^{[datasheet] [OSDev wiki]}.
  _{IO APIC LAPIC.}
   
  IO APIC, ( ) , INTINx.
  , IO APIC , INTIN0-15 IRQ0-15, .

• ^{[ OSDev]}
  (, ), . PIC , IO APIC , MSI - .
  , , .
  x86 PCI (e) LAPIC ³.

LAPIC, IRQ .
PIC

IRQ 0-7  -> INT 08h - 0fh  
IRQ 8-15 -> INT 70h - 77h  

, IRQ 08h IBM (Intel 32 ).

- IRQ, INT, , ( ACPI), .

IRQ (, ) , , , ACPI GSI .

, GSI ( ACPI, ) IRQ, , PIC GSI ( ) IO APIC - GSI .

---

, , , SCI_INT:

SCI 8259. , 8259, SCI.

, , - , , , " SCI".

SCI, , GSI, 9, , IRQ 9 ⁴. IRQ 9 INT 71h, , ACPI, IRQ , , .

, 9 , ( ACPI).

     GSI        <---->   IRQ     <---->           INT
System vector                                Interrupt vector

---

¹ .
² , 8259A .
³ LAPIC, , , SMP, QPI.
⁴ , , APIC GSI 9 IO APIC, IRQ ISA.