hv: sched: add yield support

Add yield support for schedule, which can give up pcpu proactively.

Tracked-On: #4178
Signed-off-by: Jason Chen CJ <jason.cj.chen@intel.com>
Signed-off-by: Yu Wang <yu1.wang@intel.com>
Signed-off-by: Shuo A Liu <shuo.a.liu@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

Author: Shuo A Liu

hypervisor/common/schedule.c

@@ -240,6 +240,11 @@ void kick_thread(const struct thread_object *obj)
 	release_schedule_lock(pcpu_id, rflag);
 }
 
+void yield_current(void)
+{
+	make_reschedule_request(get_pcpu_id(), DEL_MODE_IPI);
+}
+
 void run_thread(struct thread_object *obj)
 {
 	uint64_t rflag;

hypervisor/include/common/schedule.h

@@ -109,6 +109,7 @@ void run_thread(struct thread_object *obj);
 void sleep_thread(struct thread_object *obj);
 void wake_thread(struct thread_object *obj);
 void kick_thread(const struct thread_object *obj);
+void yield_current(void);
 void schedule(void);
 
 void arch_switch_to(void *prev_sp, void *next_sp);