x86_64/devices: acpi: Add support for ACPI shutdown & reboot

Add an I/O port "device" to handle requests from the kernel to shutdown
or trigger a reboot, borrowing an I/O used for ACPI on the Q35 platform.
The details of this I/O port are included in the FADT
(SLEEP_STATUS_REG/SLEEP_CONTROL_REG/RESET_REG) with the details of the
value to write in the FADT for reset (RESET_VALUE) and in the DSDT for
shutdown (S5 -> 0x05)

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

devices/src/acpi.rs

@@ -0,0 +1,52 @@
+// Copyright © 2019 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+use vmm_sys_util::eventfd::EventFd;
+use BusDevice;
+
+/// A device for handling ACPI shutdown and reboot
+pub struct AcpiShutdownDevice {
+    exit_evt: EventFd,
+    reset_evt: EventFd,
+}
+
+impl AcpiShutdownDevice {
+    /// Constructs a device that will signal the given event when the guest requests it.
+    pub fn new(exit_evt: EventFd, reset_evt: EventFd) -> AcpiShutdownDevice {
+        AcpiShutdownDevice {
+            exit_evt,
+            reset_evt,
+        }
+    }
+}
+
+// Same I/O port used for shutdown and reboot
+impl BusDevice for AcpiShutdownDevice {
+    // Spec has all fields as zero
+    fn read(&mut self, _base: u64, _offset: u64, data: &mut [u8]) {
+        for i in data.iter_mut() {
+            *i = 0;
+        }
+    }
+
+    fn write(&mut self, _base: u64, _offset: u64, data: &[u8]) {
+        if data[0] == 1 {
+            debug!("ACPI Reboot signalled");
+            if let Err(e) = self.reset_evt.write(1) {
+                error!("Error triggering ACPI reset event: {}", e);
+            }
+        }
+        // The ACPI DSDT table specifies the S5 sleep state (shutdown) as value 5
+        const S5_SLEEP_VALUE: u8 = 5;
+        const SLEEP_STATUS_EN_BIT: u8 = 5;
+        const SLEEP_VALUE_BIT: u8 = 2;
+        if data[0] == (S5_SLEEP_VALUE << SLEEP_VALUE_BIT) | (1 << SLEEP_STATUS_EN_BIT) {
+            debug!("ACPI Shutdown signalled");
+            if let Err(e) = self.exit_evt.write(1) {
+                error!("Error triggering ACPI shutdown event: {}", e);
+            }
+        }
+    }
+}

devices/src/lib.rs

@@ -19,10 +19,12 @@ extern crate vmm_sys_util;
 use std::fs::File;
 use std::{io, result};
 
+mod acpi;
 mod bus;
 pub mod ioapic;
 pub mod legacy;
 
+pub use self::acpi::AcpiShutdownDevice;
 pub use self::bus::{Bus, BusDevice, Error as BusError};
 
 pub type DeviceEventT = u16;