hv: add function to return to VM0

Emulate VM0 resume from S3 state:
 - reset BSP of VM0
 - set the BSP entry to saved VM0 wakeup vec and set BSP to real mode
 - start BSP

To match trampoline_spinlock release on ACRN Sx resume path, acquire
trampoline_spinlock if ACRN Sx enter fails.

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

Author: fyin1

hypervisor/arch/x86/guest/vm.c

@@ -285,6 +285,28 @@ void resume_vm(struct vm *vm)
 	vm->state = VM_STARTED;
 }
 
+/* Resume vm from S3 state
+ *
+ * To resume vm after guest enter S3 state:
+ * - reset BSP
+ * - BSP will be put to real mode with entry set as wakeup_vec
+ * - init_vmcs BSP. We could call init_vmcs here because we know current
+ *   pcpu is mapped to BSP of vm.
+ */
+void resume_vm_from_s3(struct vm *vm, uint32_t wakeup_vec)
+{
+	struct vcpu *bsp = vcpu_from_vid(vm, 0);
+
+	vm->state = VM_STARTED;
+
+	reset_vcpu(bsp);
+	bsp->entry_addr = (void *)(uint64_t)wakeup_vec;
+	bsp->arch_vcpu.cpu_mode = CPU_MODE_REAL;
+	init_vmcs(bsp);
+
+	schedule_vcpu(bsp);
+}
+
 /* Create vm/vcpu for vm0 */
 int prepare_vm0(void)
 {

hypervisor/arch/x86/pm.c

@@ -72,6 +72,7 @@ int enter_s3(struct vm *vm, uint32_t pm1a_cnt_val,
 {
 	uint32_t pcpu_id;
 	uint64_t pmain_entry_saved;
+	uint32_t guest_wakeup_vec32;
 	uint64_t *pmain_entry;
 
 	if (vm->pm.sx_state_data == NULL) {
@@ -83,6 +84,15 @@ int enter_s3(struct vm *vm, uint32_t pm1a_cnt_val,
 
 	pcpu_id = get_cpu_id();
 
+	/* Save the wakeup vec set by guest. Will return to guest
+	 * with this wakeup vec as entry.
+	 */
+	guest_wakeup_vec32 = *vm->pm.sx_state_data->wake_vector_32;
+
+	/* set ACRN wakeup vec instead */
+	*vm->pm.sx_state_data->wake_vector_32 =
+		(uint32_t) trampoline_start16_paddr;
+
 	/* offline all APs */
 	stop_cpus();
 
@@ -128,5 +138,8 @@ int enter_s3(struct vm *vm, uint32_t pm1a_cnt_val,
 	/* online all APs again */
 	start_cpus();
 
+	/* jump back to vm */
+	resume_vm_from_s3(vm, guest_wakeup_vec32);
+
 	return 0;
 }

hypervisor/include/arch/x86/guest/vm.h

@@ -172,6 +172,7 @@ struct vm_description {
 int shutdown_vm(struct vm *vm);
 void pause_vm(struct vm *vm);
 void resume_vm(struct vm *vm);
+void resume_vm_from_s3(struct vm *vm, uint32_t wakeup_vec);
 int start_vm(struct vm *vm);
 int create_vm(struct vm_description *vm_desc, struct vm **vm);
 int prepare_vm0(void);