virt: acrn: Do hcall_destroy_vm() before resource release

The ACRN hypervisor has scenarios which could run a real-time guest VM.
The real-time guest VM occupies dedicated CPU cores, be assigned with
dedicated PCI devices. It can run without the Service VM after boot up.
hcall_destroy_vm() returns failure when a real-time guest VM refuses.
The clearing of flag ACRN_VM_FLAG_DESTROYED causes some kernel resource
double-freed in a later acrn_vm_destroy().

Do hcall_destroy_vm() before resource release to drop this chance to
destroy the VM if hypercall fails.

Fixes: 9c5137a ("virt: acrn: Introduce VM management interfaces")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Shuo Liu <shuo.a.liu@intel.com>
Signed-off-by: Fei Li <fei1.li@intel.com>
Link: https://lore.kernel.org/r/20210722062736.15050-1-fei1.li@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Shuo Liu

drivers/virt/acrn/vm.c

@@ -64,6 +64,14 @@ int acrn_vm_destroy(struct acrn_vm *vm)
 	    test_and_set_bit(ACRN_VM_FLAG_DESTROYED, &vm->flags))
 		return 0;
 
+	ret = hcall_destroy_vm(vm->vmid);
+	if (ret < 0) {
+		dev_err(acrn_dev.this_device,
+			"Failed to destroy VM %u\n", vm->vmid);
+		clear_bit(ACRN_VM_FLAG_DESTROYED, &vm->flags);
+		return ret;
+	}
+
 	/* Remove from global VM list */
 	write_lock_bh(&acrn_vm_list_lock);
 	list_del_init(&vm->list);
@@ -78,14 +86,6 @@ int acrn_vm_destroy(struct acrn_vm *vm)
 		vm->monitor_page = NULL;
 	}
 
-	ret = hcall_destroy_vm(vm->vmid);
-	if (ret < 0) {
-		dev_err(acrn_dev.this_device,
-			"Failed to destroy VM %u\n", vm->vmid);
-		clear_bit(ACRN_VM_FLAG_DESTROYED, &vm->flags);
-		return ret;
-	}
-
 	acrn_vm_all_ram_unmap(vm);
 
 	dev_dbg(acrn_dev.this_device, "VM %u destroyed.\n", vm->vmid);