devices: schedule PostMigrationAnnouncer of all devices

After this change switches in a network should find the new location of
a VM quicker.

On-behalf-of: SAP [email protected]
Signed-off-by: Sebastian Eydam <[email protected]>

Author: amphi

virtio-devices/src/lib.rs

@@ -42,8 +42,8 @@ pub use self::balloon::Balloon;
 pub use self::block::{Block, BlockState};
 pub use self::console::{Console, ConsoleResizer, Endpoint};
 pub use self::device::{
-    DmaRemapping, VirtioCommon, VirtioDevice, VirtioInterrupt, VirtioInterruptType,
-    VirtioSharedMemoryList,
+    DmaRemapping, PostMigrationAnnouncer, VirtioCommon, VirtioDevice, VirtioInterrupt,
+    VirtioInterruptType, VirtioSharedMemoryList,
 };
 pub use self::epoll_helper::{
     EPOLL_HELPER_EVENT_LAST, EpollHelper, EpollHelperError, EpollHelperHandler,

vmm/src/device_manager.rs

@@ -16,10 +16,11 @@ use std::num::Wrapping;
 use std::os::unix::fs::OpenOptionsExt;
 use std::os::unix::io::{AsRawFd, FromRawFd};
 use std::path::{Path, PathBuf};
-use std::result;
 use std::sync::{Arc, Mutex};
+use std::time::Duration;
 #[cfg(not(target_arch = "riscv64"))]
 use std::time::Instant;
+use std::{result, thread};
 
 use acpi_tables::sdt::GenericAddress;
 use acpi_tables::{Aml, aml};
@@ -90,8 +91,8 @@ use vfio_ioctls::{VfioContainer, VfioDevice, VfioDeviceFd};
 use virtio_devices::transport::{VirtioPciDevice, VirtioPciDeviceActivator, VirtioTransport};
 use virtio_devices::vhost_user::VhostUserConfig;
 use virtio_devices::{
-    AccessPlatformMapping, ActivateError, Block, Endpoint, IommuMapping, VdpaDmaMapping,
-    VirtioMemMappingSource,
+    AccessPlatformMapping, ActivateError, Block, Endpoint, IommuMapping, PostMigrationAnnouncer,
+    VdpaDmaMapping, VirtioMemMappingSource,
 };
 use vm_allocator::{AddressAllocator, SystemAllocator};
 use vm_device::dma_mapping::ExternalDmaMapping;
@@ -5063,6 +5064,48 @@ impl DeviceManager {
             self.vfio_container = None;
         }
     }
+
+    // Calls the PostMigrationAnnouncers of each device that has one, and schedules
+    // periodic announcements. Currently only network devices use this to announce
+    // the new location of the VM to the network.
+    pub fn post_migration_announce(&self) {
+        let mut announcers: Vec<Box<dyn PostMigrationAnnouncer>> = self
+            .virtio_devices
+            .iter()
+            .filter_map(|dev| dev.virtio_device.lock().unwrap().post_migration_announcer())
+            .collect();
+
+        announcers.iter_mut().for_each(|a| a.announce_once());
+        schedule_post_migration_announces(announcers, 4, 50, 100, 450);
+    }
+}
+
+// We could make this announcer configurable.
+fn schedule_post_migration_announces(
+    mut announcers: Vec<Box<dyn PostMigrationAnnouncer>>,
+    rounds: u32,
+    initial_ms: u64,
+    step_ms: u64,
+    max_ms: u64,
+) {
+    if announcers.is_empty() || rounds == 0 {
+        return;
+    }
+
+    let _ = thread::Builder::new()
+        .name("post-migration-announcers".to_string())
+        .spawn(move || {
+            for round in 0..rounds {
+                // The first announce is done synchronous, thus we sleep at the
+                // start of the loop.
+
+                let delay = (initial_ms + (round as u64) * step_ms).min(max_ms);
+                let delay = Duration::from_millis(delay);
+                thread::sleep(delay);
+
+                announcers.iter_mut().for_each(|a| a.announce_once());
+            }
+        });
 }
 
 #[cfg(feature = "ivshmem")]
@@ -5406,6 +5449,10 @@ impl Pausable for DeviceManager {
     }
 
     fn resume(&mut self) -> result::Result<(), MigratableError> {
+        // Before resuming the devices, we active the post migration announcers
+        // of devices that have one.
+        self.post_migration_announce();
+
         for (_, device_node) in self.device_tree.lock().unwrap().iter() {
             if let Some(migratable) = &device_node.migratable {
                 migratable.lock().unwrap().resume()?;