src/arch/x86/init.c

@@ -29,6 +29,26 @@ static void x86_overwrite_pat()
     wrmsr(0x277, pat);
 }
 
+/*
+ * x86_enable_fpu - Enable Floating Point Unit
+ *
+ * This function enables the Floating Point Unit,
+ * which allows the CPU to do floating point
+ * operations.
+ *
+ * Here we do not check for FPU support but we
+ * should. However most processors support it.
+ */
+static void x86_enable_fpu()
+{
+    size_t cr4;
+	__asm__ volatile("mov %%cr4, %0" : "=r"(cr4));
+	cr4 |= 0x200;
+	__asm__ volatile("mov %0, %%cr4" :: "r"(cr4));
+    uint16_t cw = 0x37F;
+    asm volatile("fldcw %0" :: "m"(cw));
+}
+
 /*
  * x86_arch_init - Initialize x86 CPU structures
  *
@@ -42,6 +62,7 @@ static void x86_overwrite_pat()
 void x86_arch_init()
 {
     x86_overwrite_pat();
+    x86_enable_fpu();
     x86_cpu_identification();
     idt_init();
     gdt_init();