refactor(pci): move (de)allocation BAR methods out of PciDevice

PciDevice trait was defining (optional) methods to allocate and
deallocate BAR regions for devices. This logic is quite device specific
and when invoked we typically know what device it refers to exactly.
Currently, we only implement the allocate API for VirtIO devices (no
deallocation whatsoever).

Simplify things by dropping these APIs from the trait definition. Also,
remove the 32bit allocator argument from allocate_bars(); we always only
allocate a single 64-bit BAR for VirtIO devices.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Author: bchalios

src/pci/src/device.rs

@@ -8,8 +8,6 @@
 use std::sync::{Arc, Barrier};
 use std::{io, result};
 
-use vm_allocator::AddressAllocator;
-
 use crate::configuration::{self, PciBarRegionType};
 
 #[derive(Debug, thiserror::Error, displaydoc::Display)]
@@ -23,7 +21,6 @@ pub enum Error {
     /// Expected resource not found.
     MissingResource,
 }
-pub type Result<T> = std::result::Result<T, Error>;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub struct BarReprogrammingParams {
@@ -34,25 +31,6 @@ pub struct BarReprogrammingParams {
 }
 
 pub trait PciDevice: Send {
-    /// Allocates the needed PCI BARs space using the `allocate` function which takes a size and
-    /// returns an address. Returns a Vec of (GuestAddress, GuestUsize) tuples.
-    fn allocate_bars(
-        &mut self,
-        _mmio32_allocator: &mut AddressAllocator,
-        _mmio64_allocator: &mut AddressAllocator,
-    ) -> Result<()> {
-        Ok(())
-    }
-
-    /// Frees the PCI BARs previously allocated with a call to allocate_bars().
-    fn free_bars(
-        &mut self,
-        _mmio32_allocator: &mut AddressAllocator,
-        _mmio64_allocator: &mut AddressAllocator,
-    ) -> Result<()> {
-        Ok(())
-    }
-
     /// Sets a register in the configuration space.
     /// * `reg_idx` - The index of the config register to modify.
     /// * `offset` - Offset into the register.

src/vmm/src/device_manager/pci_mngr.rs

@@ -8,7 +8,7 @@ use std::sync::{Arc, Mutex};
 
 use event_manager::{MutEventSubscriber, SubscriberOps};
 use log::{debug, error, warn};
-use pci::{PciBarRegionType, PciDevice, PciDeviceError, PciRootError};
+use pci::{PciBarRegionType, PciDeviceError, PciRootError};
 use serde::{Deserialize, Serialize};
 use vm_device::BusError;
 
@@ -130,10 +130,7 @@ impl PciDevices {
         let mut resource_allocator_lock = vm.resource_allocator();
         let resource_allocator = resource_allocator_lock.deref_mut();
 
-        virtio_device.allocate_bars(
-            &mut resource_allocator.mmio32_memory,
-            &mut resource_allocator.mmio64_memory,
-        )?;
+        virtio_device.allocate_bars(&mut resource_allocator.mmio64_memory)?;
 
         let virtio_device = Arc::new(Mutex::new(virtio_device));
         pci_segment

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

@@ -359,6 +359,47 @@ impl VirtioPciDevice {
         Ok(msix_config)
     }
 
+    pub fn allocate_bars(
+        &mut self,
+        mmio64_allocator: &mut AddressAllocator,
+    ) -> std::result::Result<(), PciDeviceError> {
+        let device_clone = self.device.clone();
+        let device = device_clone.lock().unwrap();
+
+        // Allocate the virtio-pci capability BAR.
+        // See http://docs.oasis-open.org/virtio/virtio/v1.0/cs04/virtio-v1.0-cs04.html#x1-740004
+        let virtio_pci_bar_addr = mmio64_allocator
+            .allocate(
+                CAPABILITY_BAR_SIZE,
+                CAPABILITY_BAR_SIZE,
+                AllocPolicy::FirstMatch,
+            )
+            .unwrap()
+            .start();
+
+        let bar = PciBarConfiguration {
+            addr: virtio_pci_bar_addr,
+            size: CAPABILITY_BAR_SIZE,
+            idx: VIRTIO_COMMON_BAR_INDEX,
+            region_type: PciBarRegionType::Memory64BitRegion,
+            prefetchable: pci::PciBarPrefetchable::NotPrefetchable,
+        };
+
+        // The creation of the PCI BAR and its associated capabilities must
+        // happen only during the creation of a brand new VM. When a VM is
+        // restored from a known state, the BARs are already created with the
+        // right content, therefore we don't need to go through this codepath.
+        self.configuration
+            .add_pci_bar(&bar)
+            .map_err(|e| PciDeviceError::IoRegistrationFailed(virtio_pci_bar_addr, e))?;
+
+        // Once the BARs are allocated, the capabilities can be added to the PCI configuration.
+        self.add_pci_capabilities()?;
+        self.bar_region = bar;
+
+        Ok(())
+    }
+
     /// Constructs a new PCI transport for the given virtio device.
     pub fn new(
         id: String,
@@ -798,48 +839,6 @@ impl PciDevice for VirtioPciDevice {
         self.configuration.detect_bar_reprogramming(reg_idx, data)
     }
 
-    fn allocate_bars(
-        &mut self,
-        mmio32_allocator: &mut AddressAllocator,
-        mmio64_allocator: &mut AddressAllocator,
-    ) -> std::result::Result<(), PciDeviceError> {
-        let device_clone = self.device.clone();
-        let device = device_clone.lock().unwrap();
-
-        // Allocate the virtio-pci capability BAR.
-        // See http://docs.oasis-open.org/virtio/virtio/v1.0/cs04/virtio-v1.0-cs04.html#x1-740004
-        let virtio_pci_bar_addr = mmio64_allocator
-            .allocate(
-                CAPABILITY_BAR_SIZE,
-                CAPABILITY_BAR_SIZE,
-                AllocPolicy::FirstMatch,
-            )
-            .unwrap()
-            .start();
-
-        let bar = PciBarConfiguration {
-            addr: virtio_pci_bar_addr,
-            size: CAPABILITY_BAR_SIZE,
-            idx: VIRTIO_COMMON_BAR_INDEX,
-            region_type: PciBarRegionType::Memory64BitRegion,
-            prefetchable: pci::PciBarPrefetchable::NotPrefetchable,
-        };
-
-        // The creation of the PCI BAR and its associated capabilities must
-        // happen only during the creation of a brand new VM. When a VM is
-        // restored from a known state, the BARs are already created with the
-        // right content, therefore we don't need to go through this codepath.
-        self.configuration
-            .add_pci_bar(&bar)
-            .map_err(|e| PciDeviceError::IoRegistrationFailed(virtio_pci_bar_addr, e))?;
-
-        // Once the BARs are allocated, the capabilities can be added to the PCI configuration.
-        self.add_pci_capabilities()?;
-        self.bar_region = bar;
-
-        Ok(())
-    }
-
     fn move_bar(
         &mut self,
         old_base: u64,