kernel: implement cpu IDs and per-cpu variables

arch/x86_64/cpu_ctrl.S

@@ -6,3 +6,35 @@ ml_halt_cpu:
 1:	cli
 	hlt
 	jmp 1b
+
+
+	.global ml_this_cpu
+	.type ml_this_cpu, @function
+
+ml_this_cpu:
+	movq %gs:0, %rax
+	ret
+
+
+	.global rdmsr
+	.type rdmsr, @function
+
+rdmsr:
+	mov %rdi, %rcx
+	rdmsr
+	shl $32, %rdx
+	orq %rax, %rdx
+	ret
+
+	.global wrmsr
+	.type wrmsr, @function
+
+wrmsr:
+	mov %rdi, %rcx
+	mov %rsi, %rax
+	mov %rsi, %rdx
+	shr $32, %rdx
+
+	wrmsr
+
+	ret