DM: add acrn_timer api for timer emulation

We will use timerfd and epoll mechanism to emulate kinds of timers like
PIT/RTC/WDT/PMTIMER/... in device model under Linux. The api is unified
in this patch.

Compare with sigevent mechanism, timerfd has a advantage that it could
avoid race condition on resource accessing in the async sigev thread.

change log:
	v1 -> v2: add NULL pointer check for function parameter;
	v2 -> v3: rename file name of vtimer.* to timer.*;
		  rename structure name of vtimer to acrn_timer;
		  add read() in timer handler to consume I/O event;
	v3 -> v4: replace bool clock_realtime with int clockid;
		  close acrn_timer->fd properly;

Tracked-On: #1489
Signed-off-by: Victor Sun <victor.sun@intel.com>
Reviewed-by: Jian Jun Chen <jian.jun.chen@intel.com>
Acked-by: Yin Fengwei <fengwei.yin@intel.com>

devicemodel/Makefile

@@ -122,6 +122,7 @@ SRCS += core/mptbl.c
 SRCS += core/main.c
 SRCS += core/hugetlb.c
 SRCS += core/vrpmb.c
+SRCS += core/timer.c
 
 # arch
 SRCS += arch/x86/pm.c

devicemodel/core/timer.c

@@ -0,0 +1,122 @@
+/*
+ * Copyright (C) <2018> Intel Corporation
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include <sys/timerfd.h>
+
+#include "vmmapi.h"
+#include "mevent.h"
+#include "timer.h"
+
+/* We can use timerfd and epoll mechanism to emulate kinds of timers like
+ * PIT/RTC/WDT/PMTIMER/... in device model under Linux.
+ * Compare with sigevent mechanism, timerfd has a advantage that it could
+ * avoid race condition on resource accessing in the async sigev thread.
+ *
+ * Please note timerfd and epoll are all Linux specific. If the code need to be
+ * ported to other OS, we can modify the api with POSIX timers and sigevent
+ * mechanism.
+ */
+
+static void
+timer_handler(int fd __attribute__((unused)),
+		  enum ev_type t __attribute__((unused)),
+		  void *arg)
+{
+	struct acrn_timer *timer = arg;
+	uint64_t buf;
+	int32_t size;
+
+	if (timer == NULL) {
+		return;
+	}
+
+	/* Consume I/O event for default EPOLLLT type.
+	 * Here is a temporary solution, the processing could be moved to
+	 * mevent.c once EVF_TIMER is supported.
+	 */
+	size = read(timer->fd, &buf, sizeof(buf));
+	if (size < 1) {
+		fprintf(stderr, "acrn_timer read timerfd error!");
+		return;
+	}
+
+	if (timer->callback != NULL) {
+		(*timer->callback)(timer->callback_param);
+	}
+}
+
+int32_t
+acrn_timer_init(struct acrn_timer *timer, void (*cb)(void *), void *param)
+{
+	if ((timer == NULL) || (cb == NULL)) {
+		return -1;
+	}
+
+	timer->fd = -1;
+	if ((timer->clockid == CLOCK_REALTIME) ||
+			(timer->clockid == CLOCK_MONOTONIC)) {
+		timer->fd = timerfd_create(timer->clockid,
+					TFD_NONBLOCK | TFD_CLOEXEC);
+	} else {
+		perror("acrn_timer clockid is not supported.\n");
+	}
+
+	if (timer->fd <= 0) {
+		perror("acrn_timer create failed.\n");
+		return -1;
+	}
+
+	timer->mevp = mevent_add(timer->fd, EVF_READ, timer_handler, timer);
+	if (timer->mevp == NULL) {
+		close(timer->fd);
+		perror("acrn_timer mevent add failed.\n");
+		return -1;
+	}
+
+	timer->callback = cb;
+	timer->callback_param = param;
+
+	return 0;
+}
+
+void
+acrn_timer_deinit(struct acrn_timer *timer)
+{
+	if (timer == NULL) {
+		return;
+	}
+
+	if (timer->mevp != NULL) {
+		mevent_delete_close(timer->mevp);
+		timer->mevp = NULL;
+	}
+
+	timer->fd = -1;
+	timer->callback = NULL;
+	timer->callback_param = NULL;
+}
+
+int32_t
+acrn_timer_settime(struct acrn_timer *timer, struct itimerspec *new_value)
+{
+	if (timer == NULL) {
+		return -1;
+	}
+
+	return timerfd_settime(timer->fd, 0, new_value, NULL);
+}
+
+int32_t
+acrn_timer_gettime(struct acrn_timer *timer, struct itimerspec *cur_value)
+{
+	if (timer == NULL) {
+		return -1;
+	}
+
+	return timerfd_gettime(timer->fd, cur_value);
+}

devicemodel/include/timer.h

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) <2018> Intel Corporation
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef _TIMER_H_
+#define _TIMER_H_
+
+struct acrn_timer {
+	int32_t fd;
+	int32_t clockid;
+	struct mevent *mevp;
+	void (*callback)(void *);
+	void *callback_param;
+};
+
+int32_t
+acrn_timer_init(struct acrn_timer *timer, void (*cb)(void *), void *param);
+void
+acrn_timer_deinit(struct acrn_timer *timer);
+int32_t
+acrn_timer_settime(struct acrn_timer *timer, struct itimerspec *new_value);
+int32_t
+acrn_timer_gettime(struct acrn_timer *timer, struct itimerspec *cur_value);
+
+#endif /* _VTIMER_ */