From 72a38457f00ece16725c7308729654bfd5b39bb1 Mon Sep 17 00:00:00 2001
From: Fupan Li <fupan.lfp@antgroup.com>
Date: Thu, 3 Jul 2025 11:54:26 +0800
Subject: [PATCH] dragonball: make the resize_vcpu api support sync

Let dragonball's resize_vcpu api support synchronization, and only
return after the hot-plug of the CPU is successfully executed in the
guest kernel. This ensures that the subsequent device hot-plug operation
can also proceed smoothly.

Signed-off-by: Fupan Li <fupan.lfp@antgroup.com>
---
 src/dragonball/src/api/v1/vmm_action.rs             | 13 ++++++++-----
 .../src/device_manager/vfio_dev_mgr/mod.rs          |  2 +-
 src/dragonball/src/vcpu/vcpu_manager.rs             |  8 +++++---
 src/dragonball/src/vm/mod.rs                        |  2 +-
 4 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/src/dragonball/src/api/v1/vmm_action.rs b/src/dragonball/src/api/v1/vmm_action.rs
index e687bc1dfc..a0a070dd37 100644
--- a/src/dragonball/src/api/v1/vmm_action.rs
+++ b/src/dragonball/src/api/v1/vmm_action.rs
@@ -9,8 +9,9 @@
 use std::fs::File;
 use std::sync::{Arc, Mutex};
 
-use crossbeam_channel::{unbounded, Receiver, Sender, TryRecvError};
+use crossbeam_channel::{Receiver, Sender, TryRecvError};
 use log::{debug, error, info, warn};
+use std::sync::mpsc;
 use tracing::instrument;
 
 use crate::error::{Result, StartMicroVmError, StopMicrovmError};
@@ -284,7 +285,7 @@ pub enum VmmData {
     /// Return vfio device's slot number in guest.
     VfioDeviceData(Option<u8>),
     /// Sync Hotplug
-    SyncHotplug((Sender<Option<i32>>, Receiver<Option<i32>>)),
+    SyncHotplug((mpsc::Sender<Option<i32>>, mpsc::Receiver<Option<i32>>)),
 }
 
 /// Request data type used to communicate between the API and the VMM.
@@ -900,7 +901,7 @@ impl VmmService {
             }
         })?;
 
-        let (sender, receiver) = unbounded();
+        let (sender, receiver) = mpsc::channel();
 
         // It is safe because we don't expect poison lock.
         let vfio_manager = vm.device_manager.vfio_manager.lock().unwrap();
@@ -965,15 +966,17 @@ impl VmmService {
             ));
         }
 
+        let (sender, revceiver) = mpsc::channel();
+
         #[cfg(feature = "dbs-upcall")]
-        vm.resize_vcpu(config, None).map_err(|e| {
+        vm.resize_vcpu(config, Some(sender.clone())).map_err(|e| {
             if let VcpuResizeError::UpcallServerNotReady = e {
                 return VmmActionError::UpcallServerNotReady;
             }
             VmmActionError::ResizeVcpu(e)
         })?;
 
-        Ok(VmmData::Empty)
+        Ok(VmmData::SyncHotplug((sender, revceiver)))
     }
 
     #[cfg(feature = "virtio-mem")]
diff --git a/src/dragonball/src/device_manager/vfio_dev_mgr/mod.rs b/src/dragonball/src/device_manager/vfio_dev_mgr/mod.rs
index 893788c401..c3318ebb9a 100644
--- a/src/dragonball/src/device_manager/vfio_dev_mgr/mod.rs
+++ b/src/dragonball/src/device_manager/vfio_dev_mgr/mod.rs
@@ -16,9 +16,9 @@ use std::collections::HashMap;
 use std::ops::Deref;
 use std::os::fd::RawFd;
 use std::path::Path;
+use std::sync::mpsc::Sender;
 use std::sync::{Arc, Weak};
 
-use crossbeam_channel::Sender;
 use dbs_device::resources::Resource::LegacyIrq;
 use dbs_device::resources::{DeviceResources, Resource, ResourceConstraint};
 use dbs_device::DeviceIo;
diff --git a/src/dragonball/src/vcpu/vcpu_manager.rs b/src/dragonball/src/vcpu/vcpu_manager.rs
index 2d6f915981..4072d413ee 100644
--- a/src/dragonball/src/vcpu/vcpu_manager.rs
+++ b/src/dragonball/src/vcpu/vcpu_manager.rs
@@ -225,7 +225,7 @@ pub struct VcpuManager {
     vm_as: GuestAddressSpaceImpl,
     pub(crate) vm_fd: Arc<VmFd>,
 
-    action_sycn_tx: Option<Sender<bool>>,
+    action_sycn_tx: Option<Sender<Option<i32>>>,
     vcpus_in_action: (VcpuAction, Vec<u8>),
     pub(crate) reset_event_fd: Option<EventFd>,
 
@@ -756,7 +756,9 @@ impl VcpuManager {
 
     fn sync_action_finish(&mut self, got_error: bool) {
         if let Some(tx) = self.action_sycn_tx.take() {
-            if let Err(e) = tx.send(got_error) {
+            let result = if got_error { 0 } else { -1 };
+
+            if let Err(e) = tx.send(Some(result)) {
                 debug!("cpu sync action send to closed channel {}", e);
             }
         }
@@ -856,7 +858,7 @@ mod hotplug {
         pub fn resize_vcpu(
             &mut self,
             vcpu_count: u8,
-            sync_tx: Option<Sender<bool>>,
+            sync_tx: Option<Sender<Option<i32>>>,
         ) -> std::result::Result<(), VcpuResizeError> {
             if self.get_vcpus_action() != VcpuAction::None {
                 return Err(VcpuResizeError::VcpuIsHotplugging);
diff --git a/src/dragonball/src/vm/mod.rs b/src/dragonball/src/vm/mod.rs
index 37e9f408fb..7de8d52fb3 100644
--- a/src/dragonball/src/vm/mod.rs
+++ b/src/dragonball/src/vm/mod.rs
@@ -832,7 +832,7 @@ impl Vm {
     pub fn resize_vcpu(
         &mut self,
         config: VcpuResizeInfo,
-        sync_tx: Option<Sender<bool>>,
+        sync_tx: Option<Sender<Option<i32>>>,
     ) -> std::result::Result<(), VcpuResizeError> {
         if self.upcall_client().is_none() {
             Err(VcpuResizeError::UpcallClientMissing)