Merge branch 'feat_inital_context_switching' into 'develop_ba'

Implement Context Switching

See merge request teachos/kernel!6

1 files changed, 31 insertions, 0 deletions

diff --git a/arch/x86_64/src/kernel/cpu/msr.cpp b/arch/x86_64/src/kernel/cpu/msr.cpp
new file mode 100644
index 0000000..9c474a1
--- /dev/null
+++ b/arch/x86_64/src/kernel/cpu/msr.cpp
@@ -0,0 +1,31 @@
+#include "arch/kernel/cpu/msr.hpp"
+
+namespace teachos::arch::kernel::cpu
+{
+  namespace
+  {
+    auto constexpr IA32_EFER_ADDRESS = 0xC0000080;
+  }
+
+  auto read_msr(uint32_t msr) -> uint64_t
+  {
+    uint32_t low, high;
+    asm volatile("rdmsr" : "=a"(low), "=d"(high) : "c"(msr));
+    return (static_cast<uint64_t>(high) << 32) | low;
+  }
+
+  auto write_msr(uint32_t msr, uint64_t value) -> void
+  {
+    uint32_t low = value;
+    uint32_t high = value >> 32;
+    asm volatile("wrmsr"
+                 : /* no output from call */
+                 : "c"(msr), "a"(low), "d"(high));
+  }
+
+  auto set_efer_bit(efer_flags flag) -> void
+  {
+    auto const efer = read_msr(IA32_EFER_ADDRESS);
+    write_msr(IA32_EFER_ADDRESS, static_cast<std::underlying_type<efer_flags>::type>(flag) | efer);
+  }
+}  // namespace teachos::arch::kernel::cpu