vmm: Share the guest memory instead of cloning it

The VMM guest memory was cloned (copied) everywhere the code needed to
have ownership of it. In order to clean the code, and in anticipation
for future support of modifying this guest memory instance at runtime,
it is important that every part of the code share the same instance.

Because VirtioDevice implementations need to have access to it from
different threads, that's why Arc must be used in this case.

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

vfio/src/vfio_device.rs

@@ -513,14 +513,18 @@ pub struct VfioDevice {
     group: VfioGroup,
     regions: Vec<VfioRegion>,
     irqs: HashMap<u32, VfioIrq>,
-    mem: GuestMemoryMmap,
+    mem: Arc<GuestMemoryMmap>,
 }
 
 impl VfioDevice {
     /// Create a new vfio device, then guest read/write on this device could be
     /// transfered into kernel vfio.
     /// sysfspath specify the vfio device path in sys file system.
-    pub fn new(sysfspath: &Path, device_fd: Arc<DeviceFd>, mem: GuestMemoryMmap) -> Result<Self> {
+    pub fn new(
+        sysfspath: &Path,
+        device_fd: Arc<DeviceFd>,
+        mem: Arc<GuestMemoryMmap>,
+    ) -> Result<Self> {
         let uuid_path: PathBuf = [sysfspath, Path::new("iommu_group")].iter().collect();
         let group_path = uuid_path.read_link().map_err(|_| VfioError::InvalidPath)?;
         let group_osstr = group_path.file_name().ok_or(VfioError::InvalidPath)?;

vm-virtio/src/block.rs

@@ -321,7 +321,7 @@ impl Request {
 
 struct BlockEpollHandler<T: DiskFile> {
     queues: Vec<Queue>,
-    mem: GuestMemoryMmap,
+    mem: Arc<GuestMemoryMmap>,
     disk_image: T,
     disk_nsectors: u64,
     interrupt_cb: Arc<VirtioInterrupt>,
@@ -610,7 +610,7 @@ impl<T: 'static + DiskFile + Send> VirtioDevice for Block<T> {
 
     fn activate(
         &mut self,
-        mem: GuestMemoryMmap,
+        mem: Arc<GuestMemoryMmap>,
         interrupt_cb: Arc<VirtioInterrupt>,
         queues: Vec<Queue>,
         mut queue_evts: Vec<EventFd>,

vm-virtio/src/console.rs

@@ -54,7 +54,7 @@ unsafe impl ByteValued for VirtioConsoleConfig {}
 
 struct ConsoleEpollHandler {
     queues: Vec<Queue>,
-    mem: GuestMemoryMmap,
+    mem: Arc<GuestMemoryMmap>,
     interrupt_cb: Arc<VirtioInterrupt>,
     in_buffer: Arc<Mutex<VecDeque<u8>>>,
     out: Box<dyn io::Write + Send>,
@@ -432,7 +432,7 @@ impl VirtioDevice for Console {
 
     fn activate(
         &mut self,
-        mem: GuestMemoryMmap,
+        mem: Arc<GuestMemoryMmap>,
         interrupt_cb: Arc<VirtioInterrupt>,
         queues: Vec<Queue>,
         mut queue_evts: Vec<EventFd>,

vm-virtio/src/device.rs

@@ -67,7 +67,7 @@ pub trait VirtioDevice: Send {
     /// Activates this device for real usage.
     fn activate(
         &mut self,
-        mem: GuestMemoryMmap,
+        mem: Arc<GuestMemoryMmap>,
         interrupt_evt: Arc<VirtioInterrupt>,
         queues: Vec<Queue>,
         queue_evts: Vec<EventFd>,

vm-virtio/src/fs.rs

@@ -368,7 +368,7 @@ impl Fs {
 
     fn setup_vu(
         &mut self,
-        mem: &GuestMemoryMmap,
+        mem: &Arc<GuestMemoryMmap>,
         queues: Vec<Queue>,
         queue_evts: Vec<EventFd>,
     ) -> Result<Vec<(EventFd, Queue)>> {
@@ -527,7 +527,7 @@ impl VirtioDevice for Fs {
 
     fn activate(
         &mut self,
-        mem: GuestMemoryMmap,
+        mem: Arc<GuestMemoryMmap>,
         interrupt_cb: Arc<VirtioInterrupt>,
         queues: Vec<Queue>,
         queue_evts: Vec<EventFd>,

vm-virtio/src/net.rs

@@ -115,7 +115,7 @@ fn vnet_hdr_len() -> usize {
 }
 
 struct NetEpollHandler {
-    mem: GuestMemoryMmap,
+    mem: Arc<GuestMemoryMmap>,
     tap: Tap,
     rx: RxVirtio,
     tx: TxVirtio,
@@ -572,7 +572,7 @@ impl VirtioDevice for Net {
 
     fn activate(
         &mut self,
-        mem: GuestMemoryMmap,
+        mem: Arc<GuestMemoryMmap>,
         interrupt_cb: Arc<VirtioInterrupt>,
         mut queues: Vec<Queue>,
         mut queue_evts: Vec<EventFd>,

vm-virtio/src/pmem.rs

@@ -154,7 +154,7 @@ impl Request {
 
 struct PmemEpollHandler {
     queue: Queue,
-    mem: GuestMemoryMmap,
+    mem: Arc<GuestMemoryMmap>,
     disk: File,
     interrupt_cb: Arc<VirtioInterrupt>,
     queue_evt: EventFd,
@@ -382,7 +382,7 @@ impl VirtioDevice for Pmem {
 
     fn activate(
         &mut self,
-        mem: GuestMemoryMmap,
+        mem: Arc<GuestMemoryMmap>,
         interrupt_cb: Arc<VirtioInterrupt>,
         mut queues: Vec<Queue>,
         mut queue_evts: Vec<EventFd>,

vm-virtio/src/rng.rs

@@ -32,7 +32,7 @@ const KILL_EVENT: DeviceEventT = 1;
 
 struct RngEpollHandler {
     queues: Vec<Queue>,
-    mem: GuestMemoryMmap,
+    mem: Arc<GuestMemoryMmap>,
     random_file: File,
     interrupt_cb: Arc<VirtioInterrupt>,
     queue_evt: EventFd,
@@ -237,7 +237,7 @@ impl VirtioDevice for Rng {
 
     fn activate(
         &mut self,
-        mem: GuestMemoryMmap,
+        mem: Arc<GuestMemoryMmap>,
         interrupt_cb: Arc<VirtioInterrupt>,
         queues: Vec<Queue>,
         mut queue_evts: Vec<EventFd>,

vm-virtio/src/transport/pci_common_config.rs

@@ -271,7 +271,7 @@ mod tests {
         }
         fn activate(
             &mut self,
-            _mem: GuestMemoryMmap,
+            _mem: Arc<GuestMemoryMmap>,
             _interrupt_evt: Arc<VirtioInterrupt>,
             _queues: Vec<Queue>,
             _queue_evts: Vec<EventFd>,

vm-virtio/src/transport/pci_device.rs

@@ -235,7 +235,7 @@ pub struct VirtioPciDevice {
     queue_evts: Vec<EventFd>,
 
     // Guest memory
-    memory: Option<GuestMemoryMmap>,
+    memory: Option<Arc<GuestMemoryMmap>>,
 
     // Setting PCI BAR
     settings_bar: u8,
@@ -244,7 +244,7 @@ pub struct VirtioPciDevice {
 impl VirtioPciDevice {
     /// Constructs a new PCI transport for the given virtio device.
     pub fn new(
-        memory: GuestMemoryMmap,
+        memory: Arc<GuestMemoryMmap>,
         device: Box<dyn VirtioDevice>,
         msix_num: u16,
     ) -> Result<Self> {

vmm/src/vm.rs

@@ -518,7 +518,7 @@ impl Vcpu {
 }
 
 struct VmInfo<'a> {
-    memory: GuestMemoryMmap,
+    memory: &'a Arc<GuestMemoryMmap>,
     vm_fd: &'a Arc<VmFd>,
     vm_cfg: &'a VmConfig<'a>,
 }
@@ -697,7 +697,7 @@ impl DeviceManager {
                     .map_err(DeviceManagerError::CreateVirtioConsole)?;
             DeviceManager::add_virtio_pci_device(
                 Box::new(virtio_console_device),
-                vm_info.memory.clone(),
+                vm_info.memory,
                 allocator,
                 vm_info.vm_fd,
                 &mut pci,
@@ -812,7 +812,7 @@ impl DeviceManager {
 
                 DeviceManager::add_virtio_pci_device(
                     block,
-                    vm_info.memory.clone(),
+                    vm_info.memory,
                     allocator,
                     vm_info.vm_fd,
                     pci,
@@ -849,7 +849,7 @@ impl DeviceManager {
 
                 DeviceManager::add_virtio_pci_device(
                     Box::new(virtio_net_device),
-                    vm_info.memory.clone(),
+                    vm_info.memory,
                     allocator,
                     vm_info.vm_fd,
                     pci,
@@ -876,7 +876,7 @@ impl DeviceManager {
 
             DeviceManager::add_virtio_pci_device(
                 Box::new(virtio_rng_device),
-                vm_info.memory.clone(),
+                vm_info.memory,
                 allocator,
                 vm_info.vm_fd,
                 pci,
@@ -965,7 +965,7 @@ impl DeviceManager {
 
                     DeviceManager::add_virtio_pci_device(
                         Box::new(virtio_fs_device),
-                        vm_info.memory.clone(),
+                        vm_info.memory,
                         allocator,
                         vm_info.vm_fd,
                         pci,
@@ -1046,7 +1046,7 @@ impl DeviceManager {
 
                 DeviceManager::add_virtio_pci_device(
                     Box::new(virtio_pmem_device),
-                    vm_info.memory.clone(),
+                    vm_info.memory,
                     allocator,
                     vm_info.vm_fd,
                     pci,
@@ -1113,7 +1113,7 @@ impl DeviceManager {
 
     fn add_virtio_pci_device(
         virtio_device: Box<dyn vm_virtio::VirtioDevice>,
-        memory: GuestMemoryMmap,
+        memory: &Arc<GuestMemoryMmap>,
         allocator: &mut SystemAllocator,
         vm_fd: &Arc<VmFd>,
         pci: &mut PciConfigIo,
@@ -1126,7 +1126,7 @@ impl DeviceManager {
             0
         };
 
-        let mut virtio_pci_device = VirtioPciDevice::new(memory, virtio_device, msix_num)
+        let mut virtio_pci_device = VirtioPciDevice::new(memory.clone(), virtio_device, msix_num)
             .map_err(DeviceManagerError::VirtioDevice)?;
 
         let bars = virtio_pci_device
@@ -1317,7 +1317,7 @@ impl AsRawFd for EpollContext {
 pub struct Vm<'a> {
     fd: Arc<VmFd>,
     kernel: File,
-    memory: GuestMemoryMmap,
+    memory: Arc<GuestMemoryMmap>,
     vcpus: Vec<thread::JoinHandle<()>>,
     devices: DeviceManager,
     cpuid: CpuId,
@@ -1485,8 +1485,12 @@ impl<'a> Vm<'a> {
                 .ok_or(Error::MemoryRangeAllocation)?;
         }
 
+        // Convert the guest memory into an Arc. The point being able to use it
+        // anywhere in the code, no matter which thread might use it.
+        let guest_memory = Arc::new(guest_memory);
+
         let vm_info = VmInfo {
-            memory: guest_memory.clone(),
+            memory: &guest_memory,
             vm_fd: &fd,
             vm_cfg: &config,
         };
@@ -1533,7 +1537,7 @@ impl<'a> Vm<'a> {
         let cmdline_cstring =
             CString::new(self.config.cmdline.args.clone()).map_err(|_| Error::CmdLine)?;
         let entry_addr = match linux_loader::loader::Elf::load(
-            &self.memory,
+            self.memory.as_ref(),
             None,
             &mut self.kernel,
             Some(arch::HIMEM_START),
@@ -1541,7 +1545,7 @@ impl<'a> Vm<'a> {
             Ok(entry_addr) => entry_addr,
             Err(linux_loader::loader::Error::InvalidElfMagicNumber) => {
                 linux_loader::loader::BzImage::load(
-                    &self.memory,
+                    self.memory.as_ref(),
                     None,
                     &mut self.kernel,
                     Some(arch::HIMEM_START),
@@ -1552,7 +1556,7 @@ impl<'a> Vm<'a> {
         };
 
         linux_loader::loader::load_cmdline(
-            &self.memory,
+            self.memory.as_ref(),
             self.config.cmdline.offset,
             &cmdline_cstring,
         )