Splash

src/arch/x86/cpuid.c

@@ -5,14 +5,15 @@
  */
 
 #include <stdint.h>
+#include <stddef.h>
 
 /*
  * cpuid - Wrapper for CPUID instruction
- * @leaf: Requested leaf
- * @eax: EAX register value
- * @ebx: EBX register value
- * @ecx: ECX register value
- * @edx: EDX register value
+ * @leaf: Requested leaf (input EAX)
+ * @eax: EAX register value (output)
+ * @ebx: EBX register value (output)
+ * @ecx: ECX register value (output)
+ * @edx: EDX register value (output)
 */
 void cpuid(uint32_t leaf, uint32_t* eax, uint32_t* ebx, uint32_t* ecx, uint32_t* edx)
 {

src/arch/x86/init.c

@@ -4,10 +4,30 @@
  * @license GPL-3.0-only
  */
 
+#include <mem/gdt.h>
 #include <stdint.h>
 #include <arch/x86.h>
 #include <kernel.h>
 
+/*
+ * x86_overwrite_pat - Set PAT to WC
+ *
+ * This function overwrites the 1st Page Attribute
+ * Table entry, to enable the Write-Combining property
+ * when we map memory regions later on.
+ * The framebuffer will be mapped with WC, which makes
+ * memory access significantly faster by using burst
+ * operations. 
+*/
+
+static void x86_overwrite_pat()
+{
+    uint64_t pat = rdmsr(0x277);
+    pat &= ~(0xFFULL << 8); // Clear PAT1
+    pat |= (0x01ULL << 8); // PAT1 = 0x01 (WC)
+    wrmsr(0x277, pat);
+}
+
 /*
  * x86_arch_init - Initialize x86 CPU structures
  *
@@ -20,9 +40,7 @@
  */
 void x86_arch_init()
 {
-    uint64_t pat = rdmsr(0x277);
-    pat &= ~(0xFFULL << 8); // Clear PAT1
-    pat |= (0x01ULL << 8); // PAT1 = 0x01 (WC)
-    wrmsr(0x277, pat);
-    DEBUG("Overrode PAT1 entry to set up Write-Combining");
+    x86_overwrite_pat();
+    idt_init();
+    gdt_init();
 }