virtio-devices: vhost_user: Consolidate device State into VhostUserState

Each vhost-user device type had near identical State structs.
Deduplicate those by introducing a new common struct (and parameterising
it when it needs to embed a config member.) This will make it easier to
reuse more code in the future and to add more struct members to handle
the requirements of snapshot/restore.

These changes have been designed to have no impact on the existing
snapshot/restore state.

Signed-off-by: Rob Bradford <rbradford@meta.com>

virtio-devices/src/vhost_user/blk.rs

@@ -9,7 +9,6 @@ use block::VirtioBlockConfig;
 use event_monitor::event;
 use log::{error, info};
 use seccompiler::SeccompAction;
-use serde::{Deserialize, Serialize};
 use vhost::vhost_user::message::{
     VhostUserConfigFlags, VhostUserProtocolFeatures, VhostUserVirtioFeatures,
 };
@@ -29,19 +28,12 @@ use super::vu_common_ctrl::{VhostUserConfig, VhostUserHandle};
 use super::{DEFAULT_VIRTIO_FEATURES, Error, Result};
 use crate::seccomp_filters::Thread;
 use crate::thread_helper::spawn_virtio_thread;
-use crate::vhost_user::VhostUserCommon;
+use crate::vhost_user::{VhostUserCommon, VhostUserState};
 use crate::{GuestMemoryMmap, GuestRegionMmap, VIRTIO_F_ACCESS_PLATFORM, VirtioInterrupt};
 
 const DEFAULT_QUEUE_NUMBER: usize = 1;
 
-#[derive(Serialize, Deserialize)]
-pub struct State {
-    pub avail_features: u64,
-    pub acked_features: u64,
-    pub config: VirtioBlockConfig,
-    pub acked_protocol_features: u64,
-    pub vu_num_queues: usize,
-}
+pub type State = VhostUserState<VirtioBlockConfig>;
 
 struct BackendReqHandler {}
 impl VhostUserFrontendReqHandler for BackendReqHandler {}
@@ -206,6 +198,7 @@ impl Blk {
             config: self.config,
             acked_protocol_features: self.vu_common.acked_protocol_features,
             vu_num_queues: self.vu_common.vu_num_queues,
+            ..Default::default()
         }
     }
 }

virtio-devices/src/vhost_user/fs.rs

@@ -22,7 +22,7 @@ use super::vu_common_ctrl::VhostUserHandle;
 use super::{DEFAULT_VIRTIO_FEATURES, Error, Result};
 use crate::seccomp_filters::Thread;
 use crate::thread_helper::spawn_virtio_thread;
-use crate::vhost_user::VhostUserCommon;
+use crate::vhost_user::{VhostUserCommon, VhostUserState};
 use crate::{
     ActivateResult, GuestMemoryMmap, GuestRegionMmap, MmapRegion, VIRTIO_F_ACCESS_PLATFORM,
     VirtioCommon, VirtioDevice, VirtioDeviceType, VirtioInterrupt, VirtioSharedMemoryList,
@@ -31,15 +31,7 @@ use crate::{
 const NUM_QUEUE_OFFSET: usize = 1;
 const DEFAULT_QUEUE_NUMBER: usize = 2;
 
-#[derive(Serialize, Deserialize)]
-pub struct State {
-    pub avail_features: u64,
-    pub acked_features: u64,
-    pub config: VirtioFsConfig,
-    pub acked_protocol_features: u64,
-    pub vu_num_queues: usize,
-    pub backend_req_support: bool,
-}
+pub type State = VhostUserState<VirtioFsConfig>;
 
 struct BackendReqHandler {}
 impl VhostUserFrontendReqHandler for BackendReqHandler {}
@@ -215,7 +207,7 @@ impl Fs {
             config: self.config,
             acked_protocol_features: self.vu_common.acked_protocol_features,
             vu_num_queues: self.vu_common.vu_num_queues,
-            backend_req_support: false,
+            ..Default::default()
         }
     }
 }

virtio-devices/src/vhost_user/generic_vhost_user.rs

@@ -9,7 +9,6 @@ use std::{result, thread};
 use event_monitor::event;
 use log::{error, info, warn};
 use seccompiler::SeccompAction;
-use serde::{Deserialize, Serialize};
 use vhost::vhost_user::message::{
     VhostUserConfigFlags, VhostUserProtocolFeatures, VhostUserVirtioFeatures,
 };
@@ -24,20 +23,13 @@ use super::vu_common_ctrl::VhostUserHandle;
 use super::{Error, Result};
 use crate::seccomp_filters::Thread;
 use crate::thread_helper::spawn_virtio_thread;
-use crate::vhost_user::VhostUserCommon;
+use crate::vhost_user::{VhostUserCommon, VhostUserState};
 use crate::{
     ActivateResult, GuestMemoryMmap, GuestRegionMmap, MmapRegion, VIRTIO_F_ACCESS_PLATFORM,
     VirtioCommon, VirtioDevice, VirtioInterrupt, VirtioSharedMemoryList,
 };
 
-#[derive(Serialize, Deserialize)]
-pub struct State {
-    pub avail_features: u64,
-    pub acked_features: u64,
-    pub acked_protocol_features: u64,
-    pub vu_num_queues: usize,
-    pub backend_req_support: bool,
-}
+pub type State = VhostUserState<()>;
 
 struct BackendReqHandler {}
 impl VhostUserFrontendReqHandler for BackendReqHandler {}
@@ -171,6 +163,7 @@ since the backend only supports {backend_num_queues}\n",
             acked_protocol_features: self.vu_common.acked_protocol_features,
             vu_num_queues: self.vu_common.vu_num_queues,
             backend_req_support: false,
+            ..Default::default()
         }
     }
 

virtio-devices/src/vhost_user/mod.rs

@@ -295,6 +295,22 @@ impl<S: VhostUserFrontendReqHandler> EpollHelperHandler for VhostUserEpollHandle
     }
 }
 
+/// Common snapshot state for all vhost-user device types.
+///
+/// Generic over `C` which is the device-specific config type
+/// (e.g. VirtioBlockConfig, VirtioFsConfig, VirtioNetConfig).
+/// Devices without a config type use `()`.
+#[derive(Default, Serialize, Deserialize)]
+pub struct VhostUserState<C> {
+    pub avail_features: u64,
+    pub acked_features: u64,
+    pub config: C,
+    pub acked_protocol_features: u64,
+    pub vu_num_queues: usize,
+    #[serde(default)]
+    pub backend_req_support: bool,
+}
+
 #[derive(Default)]
 pub struct VhostUserCommon {
     pub vu: Option<Arc<Mutex<VhostUserHandle>>>,
@@ -441,9 +457,9 @@ impl VhostUserCommon {
         Ok(())
     }
 
-    pub fn snapshot<'a, T>(&mut self, state: &T) -> std::result::Result<Snapshot, MigratableError>
+    pub fn snapshot<T>(&mut self, state: &T) -> std::result::Result<Snapshot, MigratableError>
     where
-        T: Serialize + Deserialize<'a>,
+        T: Serialize,
     {
         let snapshot = Snapshot::new_from_state(state)?;
 

virtio-devices/src/vhost_user/net.rs

@@ -9,7 +9,6 @@ use event_monitor::event;
 use log::{error, info};
 use net_util::{CtrlQueue, MacAddr, VirtioNetConfig, build_net_config_space};
 use seccompiler::SeccompAction;
-use serde::{Deserialize, Serialize};
 use vhost::vhost_user::message::{VhostUserProtocolFeatures, VhostUserVirtioFeatures};
 use vhost::vhost_user::{FrontendReqHandler, VhostUserFrontend, VhostUserFrontendReqHandler};
 use virtio_bindings::virtio_net::{
@@ -28,7 +27,7 @@ use vmm_sys_util::eventfd::EventFd;
 use crate::seccomp_filters::Thread;
 use crate::thread_helper::spawn_virtio_thread;
 use crate::vhost_user::vu_common_ctrl::{VhostUserConfig, VhostUserHandle};
-use crate::vhost_user::{DEFAULT_VIRTIO_FEATURES, Error, Result, VhostUserCommon};
+use crate::vhost_user::{DEFAULT_VIRTIO_FEATURES, Error, Result, VhostUserCommon, VhostUserState};
 use crate::{
     ActivateResult, GuestMemoryMmap, GuestRegionMmap, NetCtrlEpollHandler,
     VIRTIO_F_ACCESS_PLATFORM, VirtioCommon, VirtioDevice, VirtioDeviceType, VirtioInterrupt,
@@ -36,14 +35,7 @@ use crate::{
 
 const DEFAULT_QUEUE_NUMBER: usize = 2;
 
-#[derive(Serialize, Deserialize)]
-pub struct State {
-    pub avail_features: u64,
-    pub acked_features: u64,
-    pub config: VirtioNetConfig,
-    pub acked_protocol_features: u64,
-    pub vu_num_queues: usize,
-}
+pub type State = VhostUserState<VirtioNetConfig>;
 
 struct BackendReqHandler {}
 impl VhostUserFrontendReqHandler for BackendReqHandler {}
@@ -235,6 +227,7 @@ impl Net {
             config: self.config,
             acked_protocol_features: self.vu_common.acked_protocol_features,
             vu_num_queues: self.vu_common.vu_num_queues,
+            ..Default::default()
         }
     }
 }