Add initialize_cpu()

Rsconscript

@@ -159,7 +159,7 @@ task "run", desc: "Run HOS in QEMU" do
   Dir.mktmpdir do |tmpdir|
     img = hello_env.expand("^/HOS.img")
     FileUtils.cp(img, tmpdir)
-    sh %W[qemu-system-x86_64 -bios OVMF.fd -drive file=#{tmpdir}/HOS.img,format=raw -device qemu-xhci -device usb-tablet]
+    sh %W[qemu-system-x86_64 -cpu max -bios OVMF.fd -drive file=#{tmpdir}/HOS.img,format=raw -device qemu-xhci -device usb-tablet]
   end
 end
 

src/hulk/cpu.d

@@ -155,6 +155,11 @@ ulong read_cr0()
     return __asm!ulong("mov %cr0, %rax", "={rax}");
 }
 
+void write_cr0(ulong v)
+{
+    __asm("mov $0, %cr0", "r", v);
+}
+
 ulong read_cr2()
 {
     return __asm!ulong("mov %cr2, %rax", "={rax}");

src/hulk/hulk.d

@@ -33,12 +33,26 @@ private __gshared HulkHeader hulk_header = {
     HULK_VIRTUAL_FRAMEBUFFER_ADDRESS, /* virt_fb_buffer */
 };
 
+private void initialize_cpu()
+{
+    /* 1. Enable SSE. */
+    /* 1.a. Turn off CR0.EM and turn on CR0.MP. */
+    write_cr0((read_cr0() & ~CR0_EM) | CR0_MP);
+    /* 1.b. Set CR4.OSFXSR and CR4.OSXMMEXCPT. */
+    write_cr4(read_cr4() | CR4_OSFXSR | CR4_OSXMMEXCPT);
+    /* 2. Enable OSXSAVE. */
+ //   write_cr4(read_cr4() | CR4_OSXSAVE);
+    /* 3. Enable AVX. */
+//    xsetbv(0u, xgetbv(0u) | XCR0_X87 | XCR0_SSE | XCR0_AVX);
+}
+
 /**
  * HULK entry point.
  */
 void hulk_start()
 {
     cli();
+    initialize_cpu();
     gdt.initialize();
     idt.initialize();
     fb.initialize(cast(uint *)HULK_VIRTUAL_FRAMEBUFFER_ADDRESS, hulk_header.bootinfo.fb.width, hulk_header.bootinfo.fb.height, hulk_header.bootinfo.fb.stride);