From 50058d32a2700352019baafb6046fec5980f104c Mon Sep 17 00:00:00 2001
From: Timo Kreuzer <timo.kreuzer@reactos.org>
Date: Fri, 9 Sep 2011 21:10:07 +0000
Subject: [PATCH] [HAL] Add a hack to work around a bug in VBox: The APIC
 emulation requires an iret instruction following closely after writing the
 EOI register. Since we return from kernel mode traps with a jmp (yes you can
 return from an interrupt with a jmp!) the EOI is never triggered, making VBox
 believe we are still serving the interrupt and keeping the PPR on high level,
 preventing following interrupts. A small asm stub now does the work of both
 writing the EOI and doing an iret.

svn path=/trunk/; revision=53665
---
 reactos/hal/halx86/apic/apic.c     | 11 ++++++++---
 reactos/hal/halx86/apic/apictrap.S | 12 ++++++++++++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/reactos/hal/halx86/apic/apic.c b/reactos/hal/halx86/apic/apic.c
index 7b151be49ff..27f5e3de706 100644
--- a/reactos/hal/halx86/apic/apic.c
+++ b/reactos/hal/halx86/apic/apic.c
@@ -609,17 +609,22 @@ HalBeginSystemInterrupt(
     return TRUE;
 }
 
+void HackEoi(void);
+
 VOID
 NTAPI
 HalEndSystemInterrupt(
     IN KIRQL OldIrql,
     IN PKTRAP_FRAME TrapFrame)
 {
+    /* Write 0 to the EndOfInterruptRegister */
+    //ApicWrite(APIC_EOI, 0);
+
+    // HACK!
+    HackEoi();
+
     /* Restore the old IRQL */
     ApicSetCurrentIrql(OldIrql);
-
-    /* Write 0 to the EndOfInterruptRegister */
-    ApicWrite(APIC_EOI, 0);
 }
 
 
diff --git a/reactos/hal/halx86/apic/apictrap.S b/reactos/hal/halx86/apic/apictrap.S
index 3a4c1cde641..2bf34d86315 100644
--- a/reactos/hal/halx86/apic/apictrap.S
+++ b/reactos/hal/halx86/apic/apictrap.S
@@ -27,6 +27,18 @@ PUBLIC _ApicSpuriousService
 TRAP_ENTRY HalpTrap0D, 0
 TRAP_ENTRY HalpApcInterrupt, KI_PUSH_FAKE_ERROR_CODE
 TRAP_ENTRY HalpDispatchInterrupt, KI_PUSH_FAKE_ERROR_CODE
+
+// VBox APIC needs an iret more or less directly following the EOI
+PUBLIC _HackEoi
+_HackEoi:
+    pushfd
+    push cs
+    push offset OnlyOnePersonKnowsHowToHackAroundVBoxBugsAndThatIsNotYou // !!
+    mov dword ptr ds:[HEX(0FFFE00B0)], 0
+    iretd
+OnlyOnePersonKnowsHowToHackAroundVBoxBugsAndThatIsNotYou:
+    ret
+
 #endif
 TRAP_ENTRY HalpClockInterrupt, KI_PUSH_FAKE_ERROR_CODE
 TRAP_ENTRY HalpProfileInterrupt, KI_PUSH_FAKE_ERROR_CODE