vm-virtio: Create new VirtioTransport trait to abstract ioeventfds

In order to group together some functions that can be shared across
virtio transport layers, this commit introduces a new trait called
VirtioTransport.

The first function of this trait being ioeventfds() as it is needed from
both virtio-mmio and virtio-pci devices, represented by MmioDevice and
VirtioPciDevice structures respectively.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vm-virtio/src/transport/mmio.rs

@@ -8,6 +8,7 @@ use std::sync::{Arc, RwLock};
 use byteorder::{ByteOrder, LittleEndian};
 use libc::EFD_NONBLOCK;
 
+use crate::transport::{VirtioTransport, NOTIFY_REG_OFFSET};
 use crate::{
     Queue, VirtioDevice, VirtioInterrupt, VirtioInterruptType, DEVICE_ACKNOWLEDGE, DEVICE_DRIVER,
     DEVICE_DRIVER_OK, DEVICE_FAILED, DEVICE_FEATURES_OK, DEVICE_INIT,
@@ -86,7 +87,7 @@ impl MmioDevice {
     /// Gets the list of queue events that must be triggered whenever the VM writes to
     /// `virtio::NOTIFY_REG_OFFSET` past the MMIO base. Each event must be triggered when the
     /// value being written equals the index of the event in this list.
-    pub fn queue_evts(&self) -> &[EventFd] {
+    fn queue_evts(&self) -> &[EventFd] {
         self.queue_evts.as_slice()
     }
 
@@ -140,6 +141,16 @@ impl MmioDevice {
     }
 }
 
+impl VirtioTransport for MmioDevice {
+    fn ioeventfds(&self, base_addr: u64) -> Vec<(&EventFd, u64)> {
+        let notify_base = base_addr + u64::from(NOTIFY_REG_OFFSET);
+        self.queue_evts()
+            .iter()
+            .map(|event| (event, notify_base))
+            .collect()
+    }
+}
+
 impl BusDevice for MmioDevice {
     fn read(&mut self, _base: u64, offset: u64, data: &mut [u8]) {
         match offset {

vm-virtio/src/transport/mod.rs

@@ -2,6 +2,7 @@
 //
 // SPDX-License-Identifier: Apache-2.0
 
+use vmm_sys_util::eventfd::EventFd;
 #[cfg(feature = "pci_support")]
 mod pci_common_config;
 #[cfg(feature = "pci_support")]
@@ -17,3 +18,7 @@ mod mmio;
 pub use mmio::MmioDevice;
 #[cfg(feature = "mmio_support")]
 pub const NOTIFY_REG_OFFSET: u32 = 0x50;
+
+pub trait VirtioTransport {
+    fn ioeventfds(&self, base_addr: u64) -> Vec<(&EventFd, u64)>;
+}

vm-virtio/src/transport/pci_device.rs

@@ -30,6 +30,7 @@ use vm_memory::{Address, ByteValued, GuestAddress, GuestMemoryMmap, GuestUsize,
 use vmm_sys_util::{errno::Result, eventfd::EventFd};
 
 use super::VirtioPciCommonConfig;
+use crate::transport::VirtioTransport;
 use crate::{
     Queue, VirtioDevice, VirtioDeviceType, VirtioInterrupt, VirtioInterruptType,
     VirtioIommuRemapping, DEVICE_ACKNOWLEDGE, DEVICE_DRIVER, DEVICE_DRIVER_OK, DEVICE_FAILED,
@@ -338,7 +339,7 @@ impl VirtioPciDevice {
     /// Gets the list of queue events that must be triggered whenever the VM writes to
     /// `virtio::NOTIFY_REG_OFFSET` past the MMIO base. Each event must be triggered when the
     /// value being written equals the index of the event in this list.
-    pub fn queue_evts(&self) -> &[EventFd] {
+    fn queue_evts(&self) -> &[EventFd] {
         self.queue_evts.as_slice()
     }
 
@@ -366,21 +367,6 @@ impl VirtioPciDevice {
         self.configuration.get_bar_addr(self.settings_bar as usize)
     }
 
-    pub fn ioeventfds(&self, bar_addr: u64) -> Vec<(&EventFd, u64, u64)> {
-        let notify_base = bar_addr + NOTIFICATION_BAR_OFFSET;
-        self.queue_evts()
-            .iter()
-            .enumerate()
-            .map(|(i, event)| {
-                (
-                    event,
-                    notify_base + i as u64 * u64::from(NOTIFY_OFF_MULTIPLIER),
-                    i as u64,
-                )
-            })
-            .collect()
-    }
-
     fn add_pci_capabilities(
         &mut self,
         settings_bar: u8,
@@ -452,6 +438,22 @@ impl VirtioPciDevice {
     }
 }
 
+impl VirtioTransport for VirtioPciDevice {
+    fn ioeventfds(&self, base_addr: u64) -> Vec<(&EventFd, u64)> {
+        let notify_base = base_addr + NOTIFICATION_BAR_OFFSET;
+        self.queue_evts()
+            .iter()
+            .enumerate()
+            .map(|(i, event)| {
+                (
+                    event,
+                    notify_base + i as u64 * u64::from(NOTIFY_OFF_MULTIPLIER),
+                )
+            })
+            .collect()
+    }
+}
+
 impl PciDevice for VirtioPciDevice {
     fn assign_pin_irq(
         &mut self,