hv: add vm restart API

And export the API to DM. DM will do system reboot/S3 resume based
on this API.

Also add the pre-assumption description for some vm APIs.

Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

hypervisor/include/common/hypercall.h

@@ -76,6 +76,20 @@ int32_t hcall_create_vm(struct vm *vm, uint64_t param);
  */
 int32_t hcall_destroy_vm(uint16_t vmid);
 
+/**
+ * @brief reset virtual machine
+ *
+ * Reset a virtual machine, it will make target VM rerun from
+ * pre-defined entry. Comparing to start vm, this function reset
+ * each vcpu state and do some initialization for guest.
+ * The function will return -1 if the target VM does not exist.
+ *
+ * @param vmid ID of the VM
+ *
+ * @return 0 on success, non-zero on error.
+ */
+int32_t hcall_reset_vm(uint16_t vmid);
+
 /**
  * @brief start virtual machine
  *