From bfd302c6559a7bcf334e2170a8d70109ac63bcbc Mon Sep 17 00:00:00 2001
From: Stefan Lankes <slankes@eonerc.rwth-aachen.de>
Date: Wed, 8 Jul 2015 20:08:53 +0200
Subject: [PATCH] clear NW bit in CR0 because it is not allowed in long mode

---
 hermit/arch/x86/kernel/entry.asm | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/hermit/arch/x86/kernel/entry.asm b/hermit/arch/x86/kernel/entry.asm
index b6ed1035a..d6d4e5c38 100644
--- a/hermit/arch/x86/kernel/entry.asm
+++ b/hermit/arch/x86/kernel/entry.asm
@@ -302,20 +302,18 @@ Lno_remap:
     or eax, (1 << 0)        ; set present bit
     mov cr3, eax
 
-    ; Set CR4
+    ; Set CR4 (PAE is already set)
     mov eax, cr4
     and eax, 0xfffbf9ff     ; disable SSE
-    or eax, (1 << 4)        ; enable PSE
-    or eax, (1 << 5)        ; enable PAE
     or eax, (1 << 7)        ; enable PGE
     mov cr4, eax
 
-    ; Set CR0
+    ; Set CR0 (PM-bit is already set)
     mov eax, cr0
     and eax, ~(1 << 30)     ; enable caching
+    and eax, ~(1 << 29)     ; disable write through caching
     and eax, ~(1 << 16)     ; allow kernel write access to read-only pages
     or eax, (1 << 31)       ; enable paging
-    or eax, (1 << 0)        ; long mode also needs PM-bit set
     mov cr0, eax
 
     lgdt [GDT64.Pointer] ; Load the 64-bit global descriptor table.