hw_x86_64_muen: Implement paravirt timer driver

The driver uses the timer page containing a vector and timer value to
implement the start_one_shot() and value() functions. The timer value
designates the absolute tick count of the next event.

The address of the time page is acquired using the get_memregion_info
Sinfo API function.

repos/base-hw/src/core/include/spec/x86_64_muen/timer.h

@@ -14,7 +14,11 @@
 #ifndef _TIMER_H_
 #define _TIMER_H_
 
-#include <base/stdint.h>
+#include <base/printf.h>
+
+/* core includes */
+#include <board.h>
+#include <sinfo.h>
 
 namespace Genode
 {
@@ -26,18 +30,75 @@ namespace Genode
 
 class Genode::Timer
 {
+	private:
+
+		enum {
+			TIMER_DISABLED = ~0ULL,
+		};
+
+		uint64_t _tics_per_ms;
+
+		struct Subject_timer
+		{
+			uint64_t value;
+			uint8_t  vector;
+		} __attribute__((packed));
+
+		struct Subject_timer * _timer_page;
+
+		inline uint64_t rdtsc()
+		{
+			uint32_t lo, hi;
+			asm volatile("rdtsc" : "=a" (lo), "=d" (hi));
+			return (uint64_t)hi << 32 | lo;
+		}
+
+		class Invalid_region {};
+
 	public:
 
-		Timer() { }
+		Timer() : _tics_per_ms(Sinfo::get_tsc_khz())
+		{
+			struct Sinfo::Memregion_info region;
+			if (!Sinfo::get_memregion_info("timer", &region)) {
+				PERR("muen-timer: Unable to retrieve time memory region");
+				throw Invalid_region();
+			}
 
-		static unsigned interrupt_id(int) { return 0; }
+			_timer_page = (Subject_timer *)region.address;
+			_timer_page->vector = Board::TIMER_VECTOR_KERNEL;
+			PINF("muen-timer: page @0x%llx, frequency %llu kHz, vector %u",
+					region.address, _tics_per_ms, _timer_page->vector);
+		}
 
-		inline void start_one_shot(uint32_t const tics, unsigned) { }
+		static unsigned interrupt_id(int)
+		{
+			return Board::TIMER_VECTOR_KERNEL;
+		}
 
-		uint32_t ms_to_tics(unsigned const ms) { return 1000; }
+		inline void start_one_shot(uint32_t const tics, unsigned)
+		{
+			_timer_page->value = rdtsc() + tics;
+		}
 
-		unsigned value(unsigned) { return 0; }
+		uint32_t ms_to_tics(unsigned const ms)
+		{
+			return ms * _tics_per_ms;
+		}
 
+		unsigned value(unsigned)
+		{
+			const uint64_t now = rdtsc();
+			if (_timer_page->value != TIMER_DISABLED
+					&& _timer_page->value > now) {
+				return _timer_page->value - now;
+			}
+			return 0;
+		}
+
+		/*
+		 * Dummies
+		 */
 		static void disable_pit(void) { }
 };