From 3e819ac797729998cf6ec83a61eabfb642aaeac8 Mon Sep 17 00:00:00 2001
From: Sebastien Boeuf <sebastien.boeuf@intel.com>
Date: Mon, 28 Oct 2019 14:29:18 -0700
Subject: [PATCH] pci: Use a weak reference to the AddressManager

Storing a strong reference to the AddressManager behind the
DeviceRelocation trait results in a cyclic reference count.
Use a weak reference to break that dependency.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
---
 pci/src/bus.rs            | 11 +++++------
 vmm/src/device_manager.rs |  7 ++++++-
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/pci/src/bus.rs b/pci/src/bus.rs
index 1519474d5..4e7db0d95 100644
--- a/pci/src/bus.rs
+++ b/pci/src/bus.rs
@@ -10,8 +10,7 @@ use byteorder::{ByteOrder, LittleEndian};
 use devices::BusDevice;
 use std;
 use std::ops::DerefMut;
-use std::sync::Arc;
-use std::sync::Mutex;
+use std::sync::{Arc, Mutex, Weak};
 use vm_memory::{Address, GuestAddress, GuestUsize};
 
 const VENDOR_ID_INTEL: u16 = 0x8086;
@@ -76,11 +75,11 @@ pub struct PciBus {
     /// Devices attached to this bus.
     /// Device 0 is host bridge.
     devices: Vec<Arc<Mutex<dyn PciDevice>>>,
-    device_reloc: Arc<dyn DeviceRelocation>,
+    device_reloc: Weak<dyn DeviceRelocation>,
 }
 
 impl PciBus {
-    pub fn new(pci_root: PciRoot, device_reloc: Arc<dyn DeviceRelocation>) -> Self {
+    pub fn new(pci_root: PciRoot, device_reloc: Weak<dyn DeviceRelocation>) -> Self {
         let mut devices: Vec<Arc<Mutex<dyn PciDevice>>> = Vec::new();
 
         devices.push(Arc::new(Mutex::new(pci_root)));
@@ -198,7 +197,7 @@ impl PciConfigIo {
 
             // Reprogram the BAR if needed
             if let Some(params) = bar_reprog_params {
-                pci_bus.device_reloc.move_bar(
+                pci_bus.device_reloc.upgrade().unwrap().move_bar(
                     params.old_base,
                     params.new_base,
                     params.len,
@@ -314,7 +313,7 @@ impl PciConfigMmio {
 
             // Reprogram the BAR if needed
             if let Some(params) = bar_reprog_params {
-                pci_bus.device_reloc.move_bar(
+                pci_bus.device_reloc.upgrade().unwrap().move_bar(
                     params.old_base,
                     params.new_base,
                     params.len,
diff --git a/vmm/src/device_manager.rs b/vmm/src/device_manager.rs
index 2926c4d1b..b710578f2 100644
--- a/vmm/src/device_manager.rs
+++ b/vmm/src/device_manager.rs
@@ -34,6 +34,8 @@ use std::os::unix::fs::OpenOptionsExt;
 use std::os::unix::io::AsRawFd;
 use std::ptr::null_mut;
 use std::result;
+#[cfg(feature = "pci_support")]
+use std::sync::Weak;
 use std::sync::{Arc, Mutex, RwLock};
 #[cfg(feature = "pci_support")]
 use vfio::{VfioDevice, VfioDmaMapping, VfioPciDevice, VfioPciError};
@@ -536,7 +538,10 @@ impl DeviceManager {
             #[cfg(feature = "pci_support")]
             {
                 let pci_root = PciRoot::new(None);
-                let mut pci_bus = PciBus::new(pci_root, address_manager.clone());
+                let mut pci_bus = PciBus::new(
+                    pci_root,
+                    Arc::downgrade(&address_manager) as Weak<dyn DeviceRelocation>,
+                );
 
                 let (mut iommu_device, iommu_mapping) = if vm_info.vm_cfg.iommu {
                     let (device, mapping) =