Changeset 27079 in vbox for trunk/src/VBox/Devices/Bus

Timestamp:

Mar 5, 2010 12:19:45 PM (15 years ago)

Author:

vboxsync

Message:

Added comments about PCI/ACPI/IOAPIC interrupt routing backdoor.

File:

• trunk/src/VBox/Devices/Bus/DevPCI.cpp (modified) (2 diffs)

trunk/src/VBox/Devices/Bus/DevPCI.cpp

@@ -653 +653 @@
     uint8_t    *pbCfg = pGlobals->PIIX3State.dev.config;
     const bool  fIsAcpiDevice = pPciDev->config[2] == 0x13 && pPciDev->config[3] == 0x71;
-    /* These two configuration space bytes enable a backdoor to trigger the irq directly on the io-apic; e.g. 64 bit Linux guests use it. */
+    /* If the two configuration space bytes at 0xde, 0xad are set to 0xbe, 0xef, a back door
+     * is opened to route PCI interrupts directly to the I/O APIC and bypass the PIC.
+     * See the \_SB_.PCI0._PRT method in vbox.dsl.
+     */
     const bool  fIsApicEnabled = pGlobals->fUseIoApic && pbCfg[0xde] == 0xbe && pbCfg[0xad] == 0xef;
     int pic_irq, pic_level;
@@ -662 +665 @@
         pPciDev->Int.s.uIrqPinState = (iLevel & PDM_IRQ_LEVEL_HIGH);
 
-        /* apic only */
+        /* Send interrupt to I/O APIC only. */
         if (fIsApicEnabled)
         {