vmm: Remove kernel based IOAPIC handling from the device manager

Previously the device setup code assumed that if no IOAPIC was passed in
then the device should be added to the kernel irqchip. As an earlier
change meant that there was always a userspace IOAPIC this kernel based
code can be removed.

The accessor still returns an Option type to leave scope for
implementing a situation without an IOAPIC (no serial or GED device).
This change does not add support no-IOAPIC mode as the original code did
not either.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

vmm/src/device_manager.rs

@@ -16,7 +16,7 @@ use devices::{ioapic, HotPlugNotificationType};
 use kvm_bindings::{kvm_irq_routing_entry, kvm_userspace_memory_region};
 use kvm_ioctls::*;
 use libc::O_TMPFILE;
-use libc::{EFD_NONBLOCK, TIOCGWINSZ};
+use libc::TIOCGWINSZ;
 
 use net_util::Tap;
 #[cfg(feature = "pci_support")]
@@ -177,23 +177,7 @@ pub enum DeviceManagerError {
 pub type DeviceManagerResult<T> = result::Result<T, DeviceManagerError>;
 
 struct InterruptInfo<'a> {
-    _ioapic: &'a Option<Arc<Mutex<ioapic::Ioapic>>>,
-}
-
-struct KernelIoapicIrq {
-    evt: EventFd,
-}
-
-impl KernelIoapicIrq {
-    fn new(evt: EventFd) -> Self {
-        KernelIoapicIrq { evt }
-    }
-}
-
-impl devices::Interrupt for KernelIoapicIrq {
-    fn deliver(&self) -> result::Result<(), io::Error> {
-        self.evt.write(1)
-    }
+    _ioapic: &'a Arc<Mutex<ioapic::Ioapic>>,
 }
 
 struct UserIoapicIrq {
@@ -415,7 +399,6 @@ impl DeviceManager {
     pub fn new(
         vm_info: &VmInfo,
         allocator: SystemAllocator,
-        userspace_ioapic: bool,
         mut mem_slots: u32,
         _exit_evt: &EventFd,
         reset_evt: &EventFd,
@@ -440,7 +423,7 @@ impl DeviceManager {
             vm_fd: vm_info.vm_fd.clone(),
         });
 
-        let ioapic = DeviceManager::add_ioapic(vm_info, &address_manager, userspace_ioapic)?;
+        let ioapic = DeviceManager::add_ioapic(vm_info, &address_manager)?;
         let interrupt_info = InterruptInfo { _ioapic: &ioapic };
 
         let console = DeviceManager::add_console_device(
@@ -494,7 +477,7 @@ impl DeviceManager {
         Ok(DeviceManager {
             address_manager,
             console,
-            ioapic,
+            ioapic: Some(ioapic),
             mmap_regions,
             cmdline_additions,
             virt_iommu,
@@ -642,23 +625,17 @@ impl DeviceManager {
     fn add_ioapic(
         vm_info: &VmInfo,
         address_manager: &Arc<AddressManager>,
-        userspace_ioapic: bool,
-    ) -> DeviceManagerResult<Option<Arc<Mutex<ioapic::Ioapic>>>> {
-        let ioapic = if userspace_ioapic {
-            // Create IOAPIC
-            let ioapic = Arc::new(Mutex::new(ioapic::Ioapic::new(
-                vm_info.vm_fd.clone(),
-                APIC_START,
-            )));
+    ) -> DeviceManagerResult<Arc<Mutex<ioapic::Ioapic>>> {
+        // Create IOAPIC
+        let ioapic = Arc::new(Mutex::new(ioapic::Ioapic::new(
+            vm_info.vm_fd.clone(),
+            APIC_START,
+        )));
 
-            address_manager
-                .mmio_bus
-                .insert(ioapic.clone(), IOAPIC_START.0, IOAPIC_SIZE)
-                .map_err(DeviceManagerError::BusError)?;
-            Some(ioapic)
-        } else {
-            None
-        };
+        address_manager
+            .mmio_bus
+            .insert(ioapic.clone(), IOAPIC_START.0, IOAPIC_SIZE)
+            .map_err(DeviceManagerError::BusError)?;
 
         Ok(ioapic)
     }
@@ -670,7 +647,7 @@ impl DeviceManager {
         address_manager: &Arc<AddressManager>,
         reset_evt: EventFd,
         exit_evt: EventFd,
-        ioapic: &Option<Arc<Mutex<ioapic::Ioapic>>>,
+        ioapic: &Arc<Mutex<ioapic::Ioapic>>,
     ) -> DeviceManagerResult<Option<Arc<Mutex<devices::AcpiGEDDevice>>>> {
         let acpi_device = Arc::new(Mutex::new(devices::AcpiShutdownDevice::new(
             exit_evt, reset_evt,
@@ -691,17 +668,9 @@ impl DeviceManager {
         // We need to hardcode this as the ACPI tables need to specify a particular IRQ and it's not possible
         // to ask the allocator for a specific one.
         let ged_irq = 5;
-        let interrupt: Box<dyn devices::Interrupt> = if let Some(ioapic) = &ioapic {
-            Box::new(UserIoapicIrq::new(ioapic.clone(), ged_irq))
-        } else {
-            let ged_evt = EventFd::new(EFD_NONBLOCK).map_err(DeviceManagerError::EventFd)?;
-            vm_info
-                .vm_fd
-                .register_irqfd(&ged_evt, ged_irq as u32)
-                .map_err(DeviceManagerError::Irq)?;
+        let interrupt: Box<dyn devices::Interrupt> =
+            Box::new(UserIoapicIrq::new(ioapic.clone(), ged_irq));
 
-            Box::new(KernelIoapicIrq::new(ged_evt))
-        };
         let ged_device = Arc::new(Mutex::new(devices::AcpiGEDDevice::new(interrupt)));
 
         address_manager
@@ -755,7 +724,7 @@ impl DeviceManager {
     fn add_console_device(
         vm_info: &VmInfo,
         address_manager: &Arc<AddressManager>,
-        ioapic: &Option<Arc<Mutex<ioapic::Ioapic>>>,
+        ioapic: &Arc<Mutex<ioapic::Ioapic>>,
         virtio_devices: &mut Vec<(Box<dyn vm_virtio::VirtioDevice>, bool)>,
     ) -> DeviceManagerResult<Arc<Console>> {
         let serial_config = vm_info.vm_cfg.lock().unwrap().serial.clone();
@@ -770,17 +739,8 @@ impl DeviceManager {
         let serial = if serial_config.mode != ConsoleOutputMode::Off {
             // Serial is tied to IRQ #4
             let serial_irq = 4;
-            let interrupt: Box<dyn devices::Interrupt> = if let Some(ioapic) = &ioapic {
-                Box::new(UserIoapicIrq::new(ioapic.clone(), serial_irq))
-            } else {
-                let serial_evt = EventFd::new(EFD_NONBLOCK).map_err(DeviceManagerError::EventFd)?;
-                vm_info
-                    .vm_fd
-                    .register_irqfd(&serial_evt, serial_irq as u32)
-                    .map_err(DeviceManagerError::Irq)?;
-
-                Box::new(KernelIoapicIrq::new(serial_evt))
-            };
+            let interrupt: Box<dyn devices::Interrupt> =
+                Box::new(UserIoapicIrq::new(ioapic.clone(), serial_irq));
 
             let serial = Arc::new(Mutex::new(devices::legacy::Serial::new(
                 interrupt,
@@ -1496,17 +1456,10 @@ impl DeviceManager {
             .allocate_irq()
             .ok_or(DeviceManagerError::AllocateIrq)?;
 
-        let interrupt: Box<dyn devices::Interrupt> = if let Some(ioapic) = interrupt_info._ioapic {
-            Box::new(UserIoapicIrq::new(ioapic.clone(), irq_num as usize))
-        } else {
-            let irqfd = EventFd::new(EFD_NONBLOCK).map_err(DeviceManagerError::EventFd)?;
-
-            vm_fd
-                .register_irqfd(&irqfd, irq_num as u32)
-                .map_err(DeviceManagerError::Irq)?;
-
-            Box::new(KernelIoapicIrq::new(irqfd))
-        };
+        let interrupt: Box<dyn devices::Interrupt> = Box::new(UserIoapicIrq::new(
+            interrupt_info._ioapic.clone(),
+            irq_num as usize,
+        ));
 
         mmio_device.assign_interrupt(interrupt);
 

vmm/src/vm.rs

@@ -380,9 +380,6 @@ impl Vm {
         cap.args[0] = ioapic::NUM_IOAPIC_PINS as u64;
         fd.enable_cap(&cap).map_err(Error::VmSetup)?;
 
-        // Because of the split irqchip, we need a userspace IOAPIC.
-        let userspace_ioapic = true;
-
         // Patch tsc deadline timer bit
         cpuid_patches.push(cpu::CpuidPatch {
             function: 1,
@@ -451,7 +448,6 @@ impl Vm {
         let device_manager = DeviceManager::new(
             &vm_info,
             allocator,
-            userspace_ioapic,
             ram_regions.len() as u32,
             &exit_evt,
             &reset_evt,