vmm: api: Be more specific on "Still pending remove vcpu" errors

fidencio · likebreath · commit d0225fe68fd1 · 2025-04-28T16:24:10.000Z
Although the CPU manager gives us a quite descriptive error, on the application side (the part calling Cloud Hypervisor) we have absolutely no way to distinguish such error from any other error that may happen when resizing a VM. With this in mind, let's be more specific and return a TooManyRequests (429) error, allowing the caller to have a chance to decide whether they want to retry the operation or not. https://datatracker.ietf.org/doc/html/rfc6585#section-4 Signed-off-by: Fabiano Fidêncio <fidencio@northflank.com>
diff --git a/vmm/src/api/http/http_endpoint.rs b/vmm/src/api/http/http_endpoint.rs
@@ -15,12 +15,14 @@ use crate::api::http::{error_response, EndpointHandler, HttpError};
 #[cfg(all(target_arch = "x86_64", feature = "guest_debug"))]
 use crate::api::VmCoredump;
 use crate::api::{
-    AddDisk, ApiAction, ApiRequest, NetConfig, VmAddDevice, VmAddFs, VmAddNet, VmAddPmem,
+    AddDisk, ApiAction, ApiError, ApiRequest, NetConfig, VmAddDevice, VmAddFs, VmAddNet, VmAddPmem,
     VmAddUserDevice, VmAddVdpa, VmAddVsock, VmBoot, VmConfig, VmCounters, VmDelete, VmNmi, VmPause,
     VmPowerButton, VmReboot, VmReceiveMigration, VmRemoveDevice, VmResize, VmResizeZone, VmRestore,
     VmResume, VmSendMigration, VmShutdown, VmSnapshot,
 };
 use crate::config::RestoreConfig;
+use crate::cpu::Error as CpuError;
+use crate::vm::Error as VmError;
 
 // /api/v1/vm.create handler
 pub struct VmCreate {}
@@ -183,7 +185,6 @@ vm_action_put_handler_body!(VmAddVdpa);
 vm_action_put_handler_body!(VmAddVsock);
 vm_action_put_handler_body!(VmAddUserDevice);
 vm_action_put_handler_body!(VmRemoveDevice);
-vm_action_put_handler_body!(VmResize);
 vm_action_put_handler_body!(VmResizeZone);
 vm_action_put_handler_body!(VmSnapshot);
 vm_action_put_handler_body!(VmReceiveMigration);
@@ -220,6 +221,34 @@ impl PutHandler for VmAddNet {
 
 impl GetHandler for VmAddNet {}
 
+impl PutHandler for VmResize {
+    fn handle_request(
+        &'static self,
+        api_notifier: EventFd,
+        api_sender: Sender<ApiRequest>,
+        body: &Option<Body>,
+        _files: Vec<File>,
+    ) -> std::result::Result<Option<Body>, HttpError> {
+        if let Some(body) = body {
+            self.send(
+                api_notifier,
+                api_sender,
+                serde_json::from_slice(body.raw())?,
+            )
+            .map_err(|e| match e {
+                ApiError::VmResize(VmError::CpuManager(CpuError::VcpuPendingRemovedVcpu)) => {
+                    HttpError::TooManyRequests
+                }
+                _ => HttpError::ApiError(e),
+            })
+        } else {
+            Err(HttpError::BadRequest)
+        }
+    }
+}
+
+impl GetHandler for VmResize {}
+
 impl PutHandler for VmRestore {
     fn handle_request(
         &'static self,
diff --git a/vmm/src/api/http/mod.rs b/vmm/src/api/http/mod.rs
@@ -52,6 +52,9 @@ pub enum HttpError {
     /// Undefined endpoints
     NotFound,
 
+    /// Too many requests
+    TooManyRequests,
+
     /// Internal Server Error
     InternalServerError,
 
@@ -65,6 +68,7 @@ impl Display for HttpError {
         match self {
             BadRequest => write!(f, "Bad Request"),
             NotFound => write!(f, "Not Found"),
+            TooManyRequests => write!(f, "Too Many Requests"),
             InternalServerError => write!(f, "Internal Server Error"),
             SerdeJsonDeserialize(serde_error) => write!(f, "{}", serde_error),
             ApiError(api_error) => write!(f, "{}", api_error),
@@ -125,6 +129,7 @@ pub trait EndpointHandler {
             Err(e @ HttpError::SerdeJsonDeserialize(_)) => {
                 error_response(e, StatusCode::BadRequest)
             }
+            Err(e @ HttpError::TooManyRequests) => error_response(e, StatusCode::TooManyRequests),
             Err(e) => error_response(e, StatusCode::InternalServerError),
         }
     }
diff --git a/vmm/src/api/openapi/cloud-hypervisor.yaml b/vmm/src/api/openapi/cloud-hypervisor.yaml
@@ -160,6 +160,8 @@ paths:
           description: The VM instance was successfully resized.
         404:
           description: The VM instance could not be resized because it is not created.
+        429:
+          description: The VM instance could not be resized because a cpu removal is still pending.
 
   /vm.resize-zone:
     put:
