hv: vmcall: fix "goto detected" violations

Remove the goto by split the function into two,
dispatch_hypercall and vmcall_vmexit_handler.

Tracked-On: #861
Signed-off-by: Huihuang Shi <huihuang.shi@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

Author: Shawnshh

hypervisor/arch/x86/guest/vmcall.c

@@ -11,35 +11,18 @@ static spinlock_t vmm_hypercall_lock = {
 	.head = 0U,
 	.tail = 0U,
 };
-/*
- * Pass return value to SOS by register rax.
- * This function should always return 0 since we shouldn't
- * deal with hypercall error in hypervisor.
- */
-int32_t vmcall_vmexit_handler(struct acrn_vcpu *vcpu)
+
+static int32_t dispatch_hypercall(struct acrn_vcpu *vcpu)
 {
-	int32_t ret = -EACCES;
 	struct acrn_vm *vm = vcpu->vm;
 	/* hypercall ID from guest*/
 	uint64_t hypcall_id = vcpu_get_gpreg(vcpu, CPU_REG_R8);
 	/* hypercall param1 from guest*/
 	uint64_t param1 = vcpu_get_gpreg(vcpu, CPU_REG_RDI);
 	/* hypercall param2 from guest*/
 	uint64_t param2 = vcpu_get_gpreg(vcpu, CPU_REG_RSI);
+	int32_t ret;
 
-	if (!is_hypercall_from_ring0()) {
-		pr_err("hypercall is only allowed from RING-0!\n");
-		goto out;
-	}
-
-	if (!is_vm0(vm) && (hypcall_id != HC_WORLD_SWITCH) &&
-		(hypcall_id != HC_INITIALIZE_TRUSTY) &&
-		(hypcall_id != HC_SAVE_RESTORE_SWORLD_CTX)) {
-		pr_err("hypercall %d is only allowed from VM0!\n", hypcall_id);
-		goto out;
-	}
-
-	/* Dispatch the hypercall handler */
 	switch (hypcall_id) {
 	case HC_SOS_OFFLINE_CPU:
 		spinlock_obtain(&vmm_hypercall_lock);
@@ -194,7 +177,34 @@ int32_t vmcall_vmexit_handler(struct acrn_vcpu *vcpu)
 		break;
 	}
 
-out:
+	return ret;
+}
+
+/*
+ * Pass return value to SOS by register rax.
+ * This function should always return 0 since we shouldn't
+ * deal with hypercall error in hypervisor.
+ */
+int32_t vmcall_vmexit_handler(struct acrn_vcpu *vcpu)
+{
+	int32_t ret;
+	struct acrn_vm *vm = vcpu->vm;
+	/* hypercall ID from guest*/
+	uint64_t hypcall_id = vcpu_get_gpreg(vcpu, CPU_REG_R8);
+
+	if (!is_hypercall_from_ring0()) {
+		pr_err("hypercall is only allowed from RING-0!\n");
+	        ret = -EACCES;
+	} else if (!is_vm0(vm) && (hypcall_id != HC_WORLD_SWITCH) &&
+		(hypcall_id != HC_INITIALIZE_TRUSTY) &&
+		(hypcall_id != HC_SAVE_RESTORE_SWORLD_CTX)) {
+		pr_err("hypercall %d is only allowed from VM0!\n", hypcall_id);
+	        ret = -EACCES;
+	} else {
+		/* Dispatch the hypercall handler */
+		ret = dispatch_hypercall(vcpu);
+	}
+
 	vcpu_set_gpreg(vcpu, CPU_REG_RAX, (uint64_t)ret);
 
 	TRACE_2L(TRACE_VMEXIT_VMCALL, vm->vm_id, hypcall_id);