kernel/x86_64: inline x86_{read, write}_msr()

This patch makes it possible to inline rdmsr and wrmsr instruction. The
performance impact shouldn't be significant since they are used relatively
rarely and wrmsr is usually a serializing instruction, but there is no reason
not to do so.

headers/private/kernel/arch/x86/64/cpu.h

@@ -9,6 +9,22 @@
 #include <arch_thread_types.h>
 
 
+static inline uint64_t
+x86_read_msr(uint32_t msr)
+{
+	uint64_t high, low;
+	asm volatile("rdmsr" : "=a" (low), "=d" (high) : "c" (msr));
+	return (high << 32) | low;
+}
+
+
+static inline void
+x86_write_msr(uint32_t msr, uint64_t value)
+{
+	asm volatile("wrmsr" : : "a" (value) , "d" (value >> 32), "c" (msr));
+}
+
+
 static inline void
 x86_context_switch(arch_thread* oldState, arch_thread* newState)
 {

headers/private/kernel/arch/x86/arch_cpu.h

@@ -461,8 +461,6 @@ void x86_fxrstor(const void* fpuState);
 void x86_noop_swap(void* oldFpuState, const void* newFpuState);
 void x86_fxsave_swap(void* oldFpuState, const void* newFpuState);
 addr_t x86_get_stack_frame();
-uint64 x86_read_msr(uint32 registerNumber);
-void x86_write_msr(uint32 registerNumber, uint64 value);
 uint32 x86_count_mtrrs(void);
 void x86_set_mtrr(uint32 index, uint64 base, uint64 length, uint8 type);
 status_t x86_get_mtrr(uint32 index, uint64* _base, uint64* _length,
@@ -481,6 +479,10 @@ void x86_hardware_interrupt(iframe* frame);
 void x86_page_fault_exception(iframe* iframe);
 
 #ifndef __x86_64__
+
+uint64 x86_read_msr(uint32 registerNumber);
+void x86_write_msr(uint32 registerNumber, uint64 value);
+
 void x86_context_switch(struct arch_thread* oldState,
 	struct arch_thread* newState);