vmm: Refactor reset func to use ResetError

Signed-off-by: Adam Jensen <adam@acj.sh>

Author: acj

src/vmm/src/devices/virtio/device.rs

@@ -11,7 +11,7 @@ use std::sync::atomic::{AtomicU32, Ordering};
 
 use vmm_sys_util::eventfd::EventFd;
 
-use super::ActivateError;
+use super::{ActivateError, ResetError};
 use super::mmio::{VIRTIO_MMIO_INT_CONFIG, VIRTIO_MMIO_INT_VRING};
 use super::queue::{Queue, QueueError};
 use crate::devices::virtio::AsAny;
@@ -175,10 +175,9 @@ pub trait VirtioDevice: AsAny + Send {
     /// Checks if the resources of this device are activated.
     fn is_activated(&self) -> bool;
 
-    /// Optionally deactivates this device and returns ownership of the guest memory map, interrupt
-    /// event, and queue events.
-    fn reset(&mut self) -> Option<(EventFd, Vec<EventFd>)> {
-        None
+    /// Optionally deactivates this device.
+    fn reset(&mut self) -> Result<(), ResetError> {
+        Err(ResetError::NotImplemented)
     }
 
     /// Mark pages used by queues as dirty.

src/vmm/src/devices/virtio/mmio.rs

@@ -204,8 +204,12 @@ impl MmioTransport {
                     let mut device_status = self.device_status;
                     let reset_result = self.locked_device().reset();
                     match reset_result {
-                        Some((_interrupt_evt, mut _queue_evts)) => {}
-                        None => {
+                        Ok(_) => {
+                            // The device MUST initialize device status to 0 upon reset.
+                            device_status = INIT;
+                        }
+                        Err(e) => {
+                            warn!("failed to reset virtio device: {:?}", e);
                             device_status |= FAILED;
                         }
                     }
@@ -471,7 +475,7 @@ pub(crate) mod tests {
         let m = single_region_mem(0x1000);
         let mut dummy = DummyDevice::new();
         // Validate reset is no-op.
-        assert!(dummy.reset().is_none());
+        assert!(dummy.reset().is_err());
         let mut d = MmioTransport::new(m, Arc::new(Mutex::new(dummy)), false);
 
         // We just make sure here that the implementation of a mmio device behaves as we expect,