From f835a75f3165281a653b891f6bb1a502cc60f65b Mon Sep 17 00:00:00 2001
From: Michael Lotz <mmlr@mlotz.ch>
Date: Sat, 13 Jun 2009 11:40:05 +0000
Subject: [PATCH] Make two runs of MTRR setting when setting memory ranges to
 write-back. At the first run only set up uncacheable MTRRs and in the second
 run set the write-back ones up. If this order is not followed, we could set
 too large ranges to cacheable first and then limit it back to uncacheable
 later. On systems with enough physical memory this would lead to a temporary
 situation in which areas become cacheable that must not be, resulting in
 system hangs or other unexpected behaviour. Fixes last part of #4018.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@31027 a95241bf-73f2-0310-859d-f6bbb57e9c96
---
 src/system/kernel/arch/x86/arch_vm.cpp | 63 ++++++++++++++++----------
 1 file changed, 39 insertions(+), 24 deletions(-)

diff --git a/src/system/kernel/arch/x86/arch_vm.cpp b/src/system/kernel/arch/x86/arch_vm.cpp
index f1c42c441b..71058a1efd 100644
--- a/src/system/kernel/arch/x86/arch_vm.cpp
+++ b/src/system/kernel/arch/x86/arch_vm.cpp
@@ -272,33 +272,48 @@ set_memory_write_back(int32 id, uint64 base, uint64 length)
 
 #ifdef TRACE_MTRR
 	dprintf("solutions: ");
-	for (int i=0; i<sSolutionCount; i++) {
-                dprintf("0x%Lx ", sSolutions[i]);
-        }
-        dprintf("\n");
+	for (int i=0; i<sSolutionCount; i++)
+		dprintf("0x%Lx ", sSolutions[i]);
+	dprintf("\n");
 #endif
 
-	bool nextDown = false;
-	for (int i = 0; i < sSolutionCount; i++) {
-		if (sSolutions[i] < 0) {
-			if (nextDown)
-				base += sSolutions[i];
-			err = set_memory_type(id, base, -sSolutions[i], nextDown ? B_MTR_UC : B_MTR_WB);
-			if (err != B_OK) {
-				dprintf("set_memory_type returned %s (0x%lx)\n", strerror(err), err);
+	for (int run = 0; run < 2; run++) {
+		bool nextDown = false;
+		uint64 newBase = base;
+
+		for (int i = 0; i < sSolutionCount; i++) {
+			if (sSolutions[i] < 0) {
+				if (nextDown)
+					newBase += sSolutions[i];
+
+				if ((run == 0) == nextDown) {
+					err = set_memory_type(id, newBase, -sSolutions[i],
+						nextDown ? B_MTR_UC : B_MTR_WB);
+					if (err != B_OK) {
+						dprintf("set_memory_type returned %s (0x%lx)\n",
+							strerror(err), err);
+					}
+				}
+
+				if (!nextDown)
+					newBase -= sSolutions[i];
+				nextDown = !nextDown;
+			} else {
+				if (nextDown)
+					newBase -= sSolutions[i];
+
+				if ((run == 0) == nextDown) {
+					err = set_memory_type(id, newBase, sSolutions[i],
+						nextDown ? B_MTR_UC : B_MTR_WB);
+					if (err != B_OK) {
+						dprintf("set_memory_type returned %s (0x%lx)\n",
+							strerror(err), err);
+					}
+				}
+
+				if (!nextDown)
+					newBase += sSolutions[i];
 			}
-			if (!nextDown)
-				base -= sSolutions[i];
-			nextDown = !nextDown;
-		} else {
-			if (nextDown)
-				base -= sSolutions[i];
-			err = set_memory_type(id, base, sSolutions[i], nextDown ? B_MTR_UC : B_MTR_WB);
-			if (err != B_OK) {
-				dprintf("set_memory_type returned %s (0x%lx)\n", strerror(err), err);
-			}
-			if (!nextDown)
-				base += sSolutions[i];
 		}
 	}
 }