From 82280e1435efd1a24e435f24cd487b5b2763563f Mon Sep 17 00:00:00 2001
From: Timo Kreuzer <timo.kreuzer@reactos.org>
Date: Wed, 6 Oct 2010 14:39:56 +0000
Subject: [PATCH] [NTOSKRNL] Alternative workaround for pentium lock errata:
 Instead of burdening the page fault handler, just mark the IDT page as
 Write-Through if the bug is present. According to
 http://www.rcollins.org/Errata/Dec97/F00FBug.html it shall prevent the lock
 up. Please test. Dedicated to elhoir.

svn path=/trunk/; revision=49018
---
 reactos/ntoskrnl/ke/amd64/cpu.c      |  1 -
 reactos/ntoskrnl/ke/i386/traphdlr.c  |  8 --------
 reactos/ntoskrnl/mm/ARM3/i386/init.c | 10 ++++++++++
 3 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/reactos/ntoskrnl/ke/amd64/cpu.c b/reactos/ntoskrnl/ke/amd64/cpu.c
index 90a6b2c0641..2e414ba3413 100644
--- a/reactos/ntoskrnl/ke/amd64/cpu.c
+++ b/reactos/ntoskrnl/ke/amd64/cpu.c
@@ -37,7 +37,6 @@ ULONG KeLargestCacheLine = 0x40;
 ULONG KiDmaIoCoherency = 0;
 CHAR KeNumberProcessors = 0;
 KAFFINITY KeActiveProcessors = 1;
-BOOLEAN KiI386PentiumLockErrataPresent;
 BOOLEAN KiSMTProcessorsPresent;
 
 /* Freeze data */
diff --git a/reactos/ntoskrnl/ke/i386/traphdlr.c b/reactos/ntoskrnl/ke/i386/traphdlr.c
index 2374bf40505..4822b71b8aa 100644
--- a/reactos/ntoskrnl/ke/i386/traphdlr.c
+++ b/reactos/ntoskrnl/ke/i386/traphdlr.c
@@ -1176,14 +1176,6 @@ KiTrap0EHandler(IN PKTRAP_FRAME TrapFrame)
     /* Save CR2 */
     Cr2 = __readcr2();
     
-    /* Check for Pentium LOCK errata */
-    if (KiI386PentiumLockErrataPresent)
-    {
-        /* Not yet implemented */
-        UNIMPLEMENTED;
-        while (TRUE);
-    }
-    
     /* HACK: Check if interrupts are disabled and enable them */
     if (!(TrapFrame->EFlags & EFLAGS_INTERRUPT_MASK))
     {
diff --git a/reactos/ntoskrnl/mm/ARM3/i386/init.c b/reactos/ntoskrnl/mm/ARM3/i386/init.c
index f561ab457db..cfb77c6e33c 100644
--- a/reactos/ntoskrnl/mm/ARM3/i386/init.c
+++ b/reactos/ntoskrnl/mm/ARM3/i386/init.c
@@ -567,6 +567,16 @@ MiInitMachineDependent(IN PLOADER_PARAMETER_BLOCK LoaderBlock)
     //
     MiFirstReservedZeroingPte->u.Hard.PageFrameNumber = MI_ZERO_PTES - 1;
     
+    /* Check for Pentium LOCK errata */
+    if (KiI386PentiumLockErrataPresent)
+    {
+        /* Mark the 1st IDT page as Write-Through to prevent a lockup
+           on a FOOF instruction. 
+           See http://www.rcollins.org/Errata/Dec97/F00FBug.html */
+        PointerPte = MiAddressToPte(KeGetPcr()->IDT);
+        PointerPte->u.Hard.WriteThrough = 1;
+    }
+
     return STATUS_SUCCESS;
 }