diff --git a/pci/src/device.rs b/pci/src/device.rs
index 99a4602b4..8f0b955fc 100644
--- a/pci/src/device.rs
+++ b/pci/src/device.rs
@@ -5,7 +5,7 @@
 use crate::configuration::{self, PciBarRegionType};
 use std::any::Any;
 use std::fmt::{self, Display};
-use std::sync::{Arc, Barrier};
+use std::sync::{Arc, Barrier, Mutex};
 use std::{self, io, result};
 use vm_allocator::{AddressAllocator, SystemAllocator};
 use vm_device::BusDevice;
@@ -51,7 +51,7 @@ pub trait PciDevice: BusDevice {
     /// returns an address. Returns a Vec of (GuestAddress, GuestUsize) tuples.
     fn allocate_bars(
         &mut self,
-        _allocator: &mut SystemAllocator,
+        _allocator: &Arc<Mutex<SystemAllocator>>,
         _mmio_allocator: &mut AddressAllocator,
     ) -> Result<Vec<(GuestAddress, GuestUsize, PciBarRegionType)>> {
         Ok(Vec::new())
diff --git a/pci/src/vfio.rs b/pci/src/vfio.rs
index 90a0d92b7..8b11b045b 100644
--- a/pci/src/vfio.rs
+++ b/pci/src/vfio.rs
@@ -15,7 +15,7 @@ use std::collections::BTreeMap;
 use std::io;
 use std::os::unix::io::AsRawFd;
 use std::ptr::null_mut;
-use std::sync::{Arc, Barrier};
+use std::sync::{Arc, Barrier, Mutex};
 use thiserror::Error;
 use vfio_bindings::bindings::vfio::*;
 use vfio_ioctls::{VfioContainer, VfioDevice, VfioIrq, VfioRegionInfoCap};
@@ -360,7 +360,7 @@ pub(crate) struct VfioCommon {
 impl VfioCommon {
     pub(crate) fn allocate_bars(
         &mut self,
-        allocator: &mut SystemAllocator,
+        allocator: &Arc<Mutex<SystemAllocator>>,
         mmio_allocator: &mut AddressAllocator,
         vfio_wrapper: &dyn Vfio,
     ) -> Result<Vec<(GuestAddress, GuestUsize, PciBarRegionType)>, PciDeviceError> {
@@ -430,6 +430,8 @@ impl VfioCommon {
 
                     // The address needs to be 4 bytes aligned.
                     bar_addr = allocator
+                        .lock()
+                        .unwrap()
                         .allocate_io_addresses(None, region_size, Some(0x4))
                         .ok_or(PciDeviceError::IoAllocationFailed(region_size))?;
                 }
@@ -476,6 +478,8 @@ impl VfioCommon {
 
                 // BAR allocation must be naturally aligned
                 bar_addr = allocator
+                    .lock()
+                    .unwrap()
                     .allocate_mmio_hole_addresses(None, region_size, Some(region_size))
                     .ok_or(PciDeviceError::IoAllocationFailed(region_size))?;
             }
@@ -1308,7 +1312,7 @@ const PCI_ROM_EXP_BAR_INDEX: usize = 12;
 impl PciDevice for VfioPciDevice {
     fn allocate_bars(
         &mut self,
-        allocator: &mut SystemAllocator,
+        allocator: &Arc<Mutex<SystemAllocator>>,
         mmio_allocator: &mut AddressAllocator,
     ) -> Result<Vec<(GuestAddress, GuestUsize, PciBarRegionType)>, PciDeviceError> {
         self.common
diff --git a/pci/src/vfio_user.rs b/pci/src/vfio_user.rs
index 56b48ac2f..cf619ec0a 100644
--- a/pci/src/vfio_user.rs
+++ b/pci/src/vfio_user.rs
@@ -389,7 +389,7 @@ impl Vfio for VfioUserClientWrapper {
 impl PciDevice for VfioUserPciDevice {
     fn allocate_bars(
         &mut self,
-        allocator: &mut SystemAllocator,
+        allocator: &Arc<Mutex<SystemAllocator>>,
         mmio_allocator: &mut AddressAllocator,
     ) -> Result<Vec<(GuestAddress, GuestUsize, PciBarRegionType)>, PciDeviceError> {
         self.common
diff --git a/virtio-devices/src/transport/pci_device.rs b/virtio-devices/src/transport/pci_device.rs
index 34f69ead2..7f3e2414d 100644
--- a/virtio-devices/src/transport/pci_device.rs
+++ b/virtio-devices/src/transport/pci_device.rs
@@ -841,7 +841,7 @@ impl PciDevice for VirtioPciDevice {
 
     fn allocate_bars(
         &mut self,
-        allocator: &mut SystemAllocator,
+        allocator: &Arc<Mutex<SystemAllocator>>,
         mmio_allocator: &mut AddressAllocator,
     ) -> std::result::Result<Vec<(GuestAddress, GuestUsize, PciBarRegionType)>, PciDeviceError>
     {
@@ -865,6 +865,8 @@ impl PciDevice for VirtioPciDevice {
         } else {
             let region_type = PciBarRegionType::Memory32BitRegion;
             let addr = allocator
+                .lock()
+                .unwrap()
                 .allocate_mmio_hole_addresses(
                     self.settings_bar_addr,
                     CAPABILITY_BAR_SIZE,
diff --git a/vmm/src/device_manager.rs b/vmm/src/device_manager.rs
index a92d5b15f..11d462feb 100644
--- a/vmm/src/device_manager.rs
+++ b/vmm/src/device_manager.rs
@@ -3088,7 +3088,7 @@ impl DeviceManager {
             .lock()
             .unwrap()
             .allocate_bars(
-                &mut self.address_manager.allocator.lock().unwrap(),
+                &self.address_manager.allocator,
                 &mut self.pci_segments[segment_id as usize]
                     .allocator
                     .lock()