[Zion] Enable SSE instructions at the start of boot.

These aren't ready to be used yet as we need to save them on task
switch.

zion/CMakeLists.txt

@@ -2,6 +2,7 @@ add_executable(zion
   boot/acpi.cpp
   boot/boot_info.cpp
   capability/capability_table.cpp
+  common/cpu.cpp
   common/gdt.cpp
   common/load_gdt.s
   common/msr.cpp

zion/common/cpu.cpp

@@ -0,0 +1,30 @@
+#include "common/cpu.h"
+
+#include <cpuid.h>
+
+#include "debug/debug.h"
+
+void ProbeCpuAndEnableFeatures() {
+  dbgln("CPUID");
+  uint32_t eax, ebx, ecx, edx;
+  __get_cpuid(1, &eax, &ebx, &ecx, &edx);
+
+  if (!(edx & (0x3 << 25))) {
+    panic("SSE & SSE2 not available.");
+  }
+
+  if (!(ecx & (0x1 | (0x1 << 9)))) {
+    panic("SSE3, SSSE3 not available.");
+  }
+
+  dbgln("Setting SSE");
+  asm volatile(
+      "mov %%cr0, %%rax;"
+      "and $0xFFFB, %%ax;"  // Clear EM
+      "or $0x2, %%ax;"      // Set MP
+      "mov %%rax, %%cr0;"
+      "mov %%cr4, %%rax;"
+      "or $0x600, %%ax;"  // Set OSFXSR, OSXMMEXCPT
+      "mov %%rax, %%cr4;" ::
+          : "rax");
+}

zion/common/cpu.h

@@ -0,0 +1,3 @@
+#pragma once
+
+void ProbeCpuAndEnableFeatures();

zion/zion.cpp

@@ -1,6 +1,7 @@
 #include <stdint.h>
 
 #include "boot/acpi.h"
+#include "common/cpu.h"
 #include "common/gdt.h"
 #include "debug/debug.h"
 #include "interrupt/apic.h"
@@ -22,6 +23,8 @@ extern "C" void zion() {
   InitGdt();
   InitIdt();
 
+  ProbeCpuAndEnableFeatures();
+
   dbgln("[boot] Init Physical Memory Manager.");
   phys_mem::InitBootstrapPageAllocation();