refactor: VirtIO MMIO persistence logic

VirtIO MMIO restore logic activates the device the moment we restore the
device state, if the device was activated when snapshotted. Move the
activation responsibility to the logic the restores the MMIO transport.
The reason for this change is that that's how it will be done for the
PCI transport. Unifying this will allow us reusing the same types for
restoring the non-transport state of devices.

Note that we needed to change the way Net devices are saved/restored.
RxBuffer type of Net devices holds RX descriptors that we have parsed
from the Queue ahead of time. The way we restored this info was
manipulating the queue to re-parse the RX descriptors during the restore
phase. However, we need the device to be activated to do so, which now
isn't. So, instead of storing this info inside the snapshot make sure we
have flushed everything before taking the snapshot.

Also, simplify a bit the types that we use for serializing/deserializing
the state of a device.

Signed-off-by: Babis Chalios <[email protected]>

Author: bchalios

src/vmm/src/device_manager/mmio.rs

@@ -15,7 +15,6 @@ use kvm_ioctls::IoEventAddress;
 use linux_loader::cmdline as kernel_cmdline;
 #[cfg(target_arch = "x86_64")]
 use log::debug;
-use log::info;
 use serde::{Deserialize, Serialize};
 use vm_allocator::AllocPolicy;
 
@@ -27,14 +26,8 @@ use crate::arch::{RTC_MEM_START, SERIAL_MEM_START};
 #[cfg(target_arch = "aarch64")]
 use crate::devices::legacy::{RTCDevice, SerialDevice};
 use crate::devices::pseudo::BootTimer;
-use crate::devices::virtio::balloon::Balloon;
-use crate::devices::virtio::block::device::Block;
 use crate::devices::virtio::device::VirtioDevice;
-use crate::devices::virtio::net::Net;
-use crate::devices::virtio::rng::Entropy;
 use crate::devices::virtio::transport::mmio::MmioTransport;
-use crate::devices::virtio::vsock::{TYPE_VSOCK, Vsock, VsockUnixBackend};
-use crate::devices::virtio::{TYPE_BALLOON, TYPE_BLOCK, TYPE_NET, TYPE_RNG};
 #[cfg(target_arch = "x86_64")]
 use crate::vstate::memory::GuestAddress;
 
@@ -441,79 +434,6 @@ impl MMIODeviceManager {
         Ok(())
     }
 
-    /// Artificially kick devices as if they had external events.
-    pub fn kick_devices(&self) {
-        info!("Artificially kick devices.");
-        // We only kick virtio devices for now.
-        let _: Result<(), MmioError> = self.for_each_virtio_device(|virtio_type, id, device| {
-            let mmio_transport_locked = device.inner.lock().expect("Poisoned locked");
-            let mut virtio = mmio_transport_locked.locked_device();
-            match *virtio_type {
-                TYPE_BALLOON => {
-                    let balloon = virtio.as_mut_any().downcast_mut::<Balloon>().unwrap();
-                    // If device is activated, kick the balloon queue(s) to make up for any
-                    // pending or in-flight epoll events we may have not captured in snapshot.
-                    // Stats queue doesn't need kicking as it is notified via a `timer_fd`.
-                    if balloon.is_activated() {
-                        info!("kick balloon {}.", id);
-                        balloon.process_virtio_queues().unwrap();
-                    }
-                }
-                TYPE_BLOCK => {
-                    // We only care about kicking virtio block.
-                    // If we need to kick vhost-user-block we can do nothing.
-                    if let Some(block) = virtio.as_mut_any().downcast_mut::<Block>() {
-                        // If device is activated, kick the block queue(s) to make up for any
-                        // pending or in-flight epoll events we may have not captured in
-                        // snapshot. No need to kick Ratelimiters
-                        // because they are restored 'unblocked' so
-                        // any inflight `timer_fd` events can be safely discarded.
-                        if block.is_activated() {
-                            info!("kick block {}.", id);
-                            block.process_virtio_queues().unwrap();
-                        }
-                    }
-                }
-                TYPE_NET => {
-                    let net = virtio.as_mut_any().downcast_mut::<Net>().unwrap();
-                    // If device is activated, kick the net queue(s) to make up for any
-                    // pending or in-flight epoll events we may have not captured in snapshot.
-                    // No need to kick Ratelimiters because they are restored 'unblocked' so
-                    // any inflight `timer_fd` events can be safely discarded.
-                    if net.is_activated() {
-                        info!("kick net {}.", id);
-                        net.process_virtio_queues().unwrap();
-                    }
-                }
-                TYPE_VSOCK => {
-                    // Vsock has complicated protocol that isn't resilient to any packet loss,
-                    // so for Vsock we don't support connection persistence through snapshot.
-                    // Any in-flight packets or events are simply lost.
-                    // Vsock is restored 'empty'.
-                    // The only reason we still `kick` it is to make guest process
-                    // `TRANSPORT_RESET_EVENT` event we sent during snapshot creation.
-                    let vsock = virtio
-                        .as_mut_any()
-                        .downcast_mut::<Vsock<VsockUnixBackend>>()
-                        .unwrap();
-                    if vsock.is_activated() {
-                        info!("kick vsock {id}.");
-                        vsock.signal_used_queue(0).unwrap();
-                    }
-                }
-                TYPE_RNG => {
-                    let entropy = virtio.as_mut_any().downcast_mut::<Entropy>().unwrap();
-                    if entropy.is_activated() {
-                        info!("kick entropy {id}.");
-                        entropy.process_virtio_queues().unwrap();
-                    }
-                }
-                _ => (),
-            }
-            Ok(())
-        });
-    }
-
     #[cfg(target_arch = "aarch64")]
     pub fn virtio_device_info(&self) -> Vec<&MMIODeviceInfo> {
         let mut device_info = Vec::new();

src/vmm/src/device_manager/mod.rs

@@ -5,6 +5,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the THIRD-PARTY file.
 
+use std::convert::Infallible;
 use std::fmt::Debug;
 use std::sync::{Arc, Mutex};
 
@@ -13,7 +14,7 @@ use event_manager::{MutEventSubscriber, SubscriberOps};
 #[cfg(target_arch = "x86_64")]
 use legacy::{LegacyDeviceError, PortIODeviceManager};
 use linux_loader::loader::Cmdline;
-use log::error;
+use log::{error, info};
 use mmio::{MMIODeviceManager, MmioError};
 use pci_mngr::{PciDevices, PciDevicesConstructorArgs, PciManagerError};
 use persist::{ACPIDeviceManagerConstructorArgs, MMIODevManagerConstructorArgs};
@@ -30,8 +31,14 @@ use crate::devices::legacy::RTCDevice;
 use crate::devices::legacy::serial::SerialOut;
 use crate::devices::legacy::{IER_RDA_BIT, IER_RDA_OFFSET, SerialDevice};
 use crate::devices::pseudo::BootTimer;
+use crate::devices::virtio::balloon::Balloon;
+use crate::devices::virtio::block::device::Block;
 use crate::devices::virtio::device::VirtioDevice;
+use crate::devices::virtio::net::Net;
+use crate::devices::virtio::rng::Entropy;
 use crate::devices::virtio::transport::mmio::{IrqTrigger, MmioTransport};
+use crate::devices::virtio::vsock::{TYPE_VSOCK, Vsock, VsockUnixBackend};
+use crate::devices::virtio::{TYPE_BALLOON, TYPE_BLOCK, TYPE_NET, TYPE_RNG};
 use crate::resources::VmResources;
 use crate::snapshot::Persist;
 use crate::vstate::memory::GuestMemoryMmap;
@@ -274,6 +281,106 @@ impl DeviceManager {
         self.pci_devices
             .attach_pci_segment(&self.resource_allocator)
     }
+
+    fn do_kick_device(virtio_device: Arc<Mutex<dyn VirtioDevice>>) {
+        let mut device = virtio_device.lock().expect("Poisoned lock");
+        match device.device_type() {
+            TYPE_BALLOON => {
+                let balloon = device.as_mut_any().downcast_mut::<Balloon>().unwrap();
+                // If device is activated, kick the balloon queue(s) to make up for any
+                // pending or in-flight epoll events we may have not captured in snapshot.
+                // Stats queue doesn't need kicking as it is notified via a `timer_fd`.
+                if balloon.is_activated() {
+                    info!("kick balloon {}.", balloon.id());
+                    balloon.process_virtio_queues().unwrap();
+                }
+            }
+            TYPE_BLOCK => {
+                // We only care about kicking virtio block.
+                // If we need to kick vhost-user-block we can do nothing.
+                if let Some(block) = device.as_mut_any().downcast_mut::<Block>() {
+                    // If device is activated, kick the block queue(s) to make up for any
+                    // pending or in-flight epoll events we may have not captured in
+                    // snapshot. No need to kick Ratelimiters
+                    // because they are restored 'unblocked' so
+                    // any inflight `timer_fd` events can be safely discarded.
+                    if block.is_activated() {
+                        info!("kick block {}.", block.id());
+                        block.process_virtio_queues().unwrap();
+                    }
+                }
+            }
+            TYPE_NET => {
+                let net = device.as_mut_any().downcast_mut::<Net>().unwrap();
+                // If device is activated, kick the net queue(s) to make up for any
+                // pending or in-flight epoll events we may have not captured in snapshot.
+                // No need to kick Ratelimiters because they are restored 'unblocked' so
+                // any inflight `timer_fd` events can be safely discarded.
+                if net.is_activated() {
+                    info!("kick net {}.", net.id());
+                    net.process_virtio_queues().unwrap();
+                }
+            }
+            TYPE_VSOCK => {
+                // Vsock has complicated protocol that isn't resilient to any packet loss,
+                // so for Vsock we don't support connection persistence through snapshot.
+                // Any in-flight packets or events are simply lost.
+                // Vsock is restored 'empty'.
+                // The only reason we still `kick` it is to make guest process
+                // `TRANSPORT_RESET_EVENT` event we sent during snapshot creation.
+                let vsock = device
+                    .as_mut_any()
+                    .downcast_mut::<Vsock<VsockUnixBackend>>()
+                    .unwrap();
+                if vsock.is_activated() {
+                    info!("kick vsock {}.", vsock.id());
+                    vsock.signal_used_queue(0).unwrap();
+                }
+            }
+            TYPE_RNG => {
+                let entropy = device.as_mut_any().downcast_mut::<Entropy>().unwrap();
+                if entropy.is_activated() {
+                    info!("kick entropy {}.", entropy.id());
+                    entropy.process_virtio_queues().unwrap();
+                }
+            }
+            _ => (),
+        }
+    }
+
+    /// Artificially kick VirtIO devices as if they had external events.
+    pub fn kick_virtio_devices(&self) {
+        info!("Artificially kick devices");
+        // Go through MMIO VirtIO devices
+        let _: Result<(), MmioError> = self.mmio_devices.for_each_virtio_device(|_, _, device| {
+            let mmio_transport_locked = device.inner.lock().expect("Poisoned lock");
+            Self::do_kick_device(mmio_transport_locked.device());
+            Ok(())
+        });
+    }
+
+    fn do_mark_virtio_queue_memory_dirty(
+        device: Arc<Mutex<dyn VirtioDevice>>,
+        mem: &GuestMemoryMmap,
+    ) {
+        // SAFETY:
+        // This should never fail as we mark pages only if device has already been activated,
+        // and the address validation was already performed on device activation.
+        let mut locked_device = device.lock().expect("Poisoned lock");
+        if locked_device.is_activated() {
+            locked_device.mark_queue_memory_dirty(mem).unwrap()
+        }
+    }
+
+    /// Mark queue memory dirty for activated VirtIO devices
+    pub fn mark_virtio_queue_memory_dirty(&self, mem: &GuestMemoryMmap) {
+        // Go through MMIO VirtIO devices
+        let _: Result<(), Infallible> = self.mmio_devices.for_each_virtio_device(|_, _, device| {
+            let mmio_transport_locked = device.inner.lock().expect("Poisoned locked");
+            Self::do_mark_virtio_queue_memory_dirty(mmio_transport_locked.device(), mem);
+            Ok(())
+        });
+    }
 }
 
 #[derive(Debug, Default, Clone, Serialize, Deserialize)]