devices: Add ACPI GED device

This device provides the ability to notify the kernel via interrupt that
there is some new hotplug activity. The type is determined by reading
from the I/O port.

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

devices/src/acpi.rs

@@ -5,6 +5,8 @@
 
 use vmm_sys_util::eventfd::EventFd;
 use BusDevice;
+use HotPlugNotificationType;
+use Interrupt;
 
 /// A device for handling ACPI shutdown and reboot
 pub struct AcpiShutdownDevice {
@@ -50,3 +52,37 @@ impl BusDevice for AcpiShutdownDevice {
         }
     }
 }
+
+/// A device for handling ACPI GED event generation
+pub struct AcpiGEDDevice {
+    interrupt: Box<dyn Interrupt>,
+    notification_type: HotPlugNotificationType,
+}
+
+impl AcpiGEDDevice {
+    pub fn new(interrupt: Box<dyn Interrupt>) -> AcpiGEDDevice {
+        AcpiGEDDevice {
+            interrupt,
+            notification_type: HotPlugNotificationType::NoDevicesChanged,
+        }
+    }
+
+    pub fn notify(
+        &mut self,
+        notification_type: HotPlugNotificationType,
+    ) -> Result<(), std::io::Error> {
+        self.notification_type = notification_type;
+        self.interrupt.deliver()
+    }
+}
+
+// I/O port reports what type of notification was made
+impl BusDevice for AcpiGEDDevice {
+    // Spec has all fields as zero
+    fn read(&mut self, _base: u64, _offset: u64, data: &mut [u8]) {
+        data[0] = self.notification_type as u8;
+        self.notification_type = HotPlugNotificationType::NoDevicesChanged;
+    }
+
+    fn write(&mut self, _base: u64, _offset: u64, _data: &[u8]) {}
+}

devices/src/lib.rs

@@ -26,7 +26,7 @@ pub mod ioapic;
 pub mod legacy;
 
 #[cfg(feature = "acpi")]
-pub use self::acpi::AcpiShutdownDevice;
+pub use self::acpi::{AcpiGEDDevice, AcpiShutdownDevice};
 pub use self::bus::{Bus, BusDevice, Error as BusError};
 
 pub type DeviceEventT = u16;
@@ -70,3 +70,9 @@ pub enum Error {
 pub trait Interrupt: Send + Sync {
     fn deliver(&self) -> result::Result<(), std::io::Error>;
 }
+
+#[derive(Clone, Copy)]
+pub enum HotPlugNotificationType {
+    NoDevicesChanged,
+    CPUDevicesChanged,
+}