interrupt: Initial interrupt manager traits

src/interrupt/mod.rs

@@ -0,0 +1,208 @@
+// Copyright (C) 2019 Alibaba Cloud. All rights reserved.
+// Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// Copyright © 2019 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0 OR BSD-3-Clause
+
+//! Traits and Structs to manage interrupt sources for devices.
+//!
+//! In system programming, an interrupt is a signal to the processor emitted by hardware or
+//! software indicating an event that needs immediate attention. An interrupt alerts the processor
+//! to a high-priority condition requiring the interruption of the current code the processor is
+//! executing. The processor responds by suspending its current activities, saving its state, and
+//! executing a function called an interrupt handler (or an interrupt service routine, ISR) to deal
+//! with the event. This interruption is temporary, and, after the interrupt handler finishes,
+//! unless handling the interrupt has emitted a fatal error, the processor resumes normal
+//! activities.
+//!
+//! Hardware interrupts are used by devices to communicate that they require attention from the
+//! operating system, or a bare-metal program running on the CPU if there are no OSes. The act of
+//! initiating a hardware interrupt is referred to as an interrupt request (IRQ). Different devices
+//! are usually associated with different interrupts using a unique value associated with each
+//! interrupt. This makes it possible to know which hardware device caused which interrupts.
+//! These interrupt values are often called IRQ lines, or just interrupt lines.
+//!
+//! Nowadays, IRQ lines is not the only mechanism to deliver device interrupts to processors.
+//! MSI [(Message Signaled Interrupt)](https://en.wikipedia.org/wiki/Message_Signaled_Interrupts)
+//! is another commonly used alternative in-band method of signaling an interrupt, using special
+//! in-band messages to replace traditional out-of-band assertion of dedicated interrupt lines.
+//! While more complex to implement in a device, message signaled interrupts have some significant
+//! advantages over pin-based out-of-band interrupt signaling. Message signaled interrupts are
+//! supported in PCI bus since its version 2.2, and in later available PCI Express bus. Some
+//! non-PCI architectures also use message signaled interrupts.
+//!
+//! While IRQ is a term commonly used by Operating Systems when dealing with hardware
+//! interrupts, the IRQ numbers managed by OSes are independent of the ones managed by VMM.
+//! For simplicity sake, the term `Interrupt Source` is used instead of IRQ to represent both
+//! pin-based interrupts and MSI interrupts.
+//!
+//! A device may support multiple types of interrupts, and each type of interrupt may support one
+//! or multiple interrupt sources. For example, a PCI device may support:
+//! * Legacy Irq: exactly one interrupt source.
+//! * PCI MSI Irq: 1,2,4,8,16,32 interrupt sources.
+//! * PCI MSIx Irq: 2^n(n=0-11) interrupt sources.
+//!
+//! A distinct Interrupt Source Identifier (ISID) will be assigned to each interrupt source.
+//! An ID allocator will be used to allocate and free Interrupt Source Identifiers for devices.
+//! To decouple the vm-device crate from the ID allocator, the vm-device crate doesn't take the
+//! responsibility to allocate/free Interrupt Source IDs but only makes use of assigned IDs.
+//!
+//! The overall flow to deal with interrupts is:
+//! * The VMM creates an interrupt manager
+//! * The VMM creates a device manager, passing on an reference to the interrupt manager
+//! * The device manager passes on an reference to the interrupt manager to all registered devices
+//! * The guest kernel loads drivers for virtual devices
+//! * The guest device driver determines the type and number of interrupts needed, and update the
+//!   device configuration
+//! * The virtual device backend requests the interrupt manager to create an interrupt group
+//!   according to guest configuration information
+
+use std::fs::File;
+use std::sync::Arc;
+
+/// Reuse std::io::Result to simplify interoperability among crates.
+pub type Result<T> = std::io::Result<T>;
+
+/// Data type to store an interrupt source identifier.
+pub type InterruptIndex = u32;
+
+/// Configuration data for legacy, pin based interrupt groups.
+///
+/// A legacy interrupt group only takes one irq number as its configuration.
+#[derive(Copy, Clone, Debug)]
+pub struct LegacyIrqGroupConfig {
+    /// Legacy irq number.
+    pub irq: InterruptIndex,
+}
+
+/// Configuration data for MSI/MSI-X interrupt groups
+///
+/// MSI/MSI-X interrupt groups are basically a set of vectors.
+#[derive(Copy, Clone, Debug)]
+pub struct MsiIrqGroupConfig {
+    /// First index of the MSI/MSI-X interrupt vectors
+    pub base: InterruptIndex,
+    /// Number of vectors in the MSI/MSI-X group.
+    pub count: InterruptIndex,
+}
+
+/// Trait to manage interrupt sources for virtual device backends.
+///
+/// The InterruptManager implementations should protect itself from concurrent accesses internally,
+/// so it could be invoked from multi-threaded context.
+pub trait InterruptManager {
+    type GroupConfig;
+
+    /// Create an [InterruptSourceGroup](trait.InterruptSourceGroup.html) object to manage
+    /// interrupt sources for a virtual device
+    ///
+    /// An [InterruptSourceGroup](trait.InterruptSourceGroup.html) object manages all interrupt
+    /// sources of the same type for a virtual device.
+    ///
+    /// # Arguments
+    /// * config: The interrupt group configuration
+    fn create_group(&self, config: Self::GroupConfig)
+        -> Result<Arc<Box<dyn InterruptSourceGroup>>>;
+
+    /// Destroy an [InterruptSourceGroup](trait.InterruptSourceGroup.html) object created by
+    /// [create_group()](trait.InterruptManager.html#tymethod.create_group).
+    ///
+    /// Assume the caller takes the responsibility to disable all interrupt sources of the group
+    /// before calling destroy_group(). This assumption helps to simplify InterruptSourceGroup
+    /// implementations.
+    fn destroy_group(&mut self, group: Arc<Box<dyn InterruptSourceGroup>>) -> Result<()>;
+}
+
+/// Configuration data for legacy interrupts.
+///
+/// On x86 platforms, legacy interrupts means those interrupts routed through PICs or IOAPICs.
+#[derive(Copy, Clone, Debug)]
+pub struct LegacyIrqSourceConfig {}
+
+/// Configuration data for MSI/MSI-X interrupts.
+///
+/// On x86 platforms, these interrupts are vectors delivered directly to the LAPIC.
+#[derive(Copy, Clone, Debug, Default)]
+pub struct MsiIrqSourceConfig {
+    /// High address to delivery message signaled interrupt.
+    pub high_addr: u32,
+    /// Low address to delivery message signaled interrupt.
+    pub low_addr: u32,
+    /// Data to write to delivery message signaled interrupt.
+    pub data: u32,
+}
+
+/// Configuration data for an interrupt source.
+#[derive(Copy, Clone, Debug)]
+pub enum InterruptSourceConfig {
+    /// Configuration data for Legacy interrupts.
+    LegacyIrq(LegacyIrqSourceConfig),
+    /// Configuration data for PciMsi, PciMsix and generic MSI interrupts.
+    MsiIrq(MsiIrqSourceConfig),
+}
+
+pub trait InterruptSourceGroup: Send + Sync {
+    /// Enable the interrupt sources in the group to generate interrupts.
+    fn enable(&mut self) -> Result<()> {
+        // Not all interrupt sources can be enabled.
+        // To accommodate this, we can have a no-op here.
+        Ok(())
+    }
+
+    /// Disable the interrupt sources in the group to generate interrupts.
+    fn disable(&mut self) -> Result<()> {
+        // Not all interrupt sources can be disabled.
+        // To accommodate this, we can have a no-op here.
+        Ok(())
+    }
+
+    /// Inject an interrupt from this interrupt source into the guest.
+    ///
+    /// # Arguments
+    /// * index: sub-index into the group.
+    fn trigger(&self, index: InterruptIndex) -> Result<()>;
+
+    /// Returns an interrupt notifier from this interrupt.
+    ///
+    /// An interrupt notifier allows for external components and processes
+    /// to inject interrupts into a guest, by writing to the file returned
+    /// by this method.
+    #[allow(unused_variables)]
+    fn notifier(&self, index: InterruptIndex) -> Option<File> {
+        // One use case of the notifier is to implement vhost user backends.
+        // For all other implementations we can just return None here.
+        None
+    }
+
+    /// Update the interrupt source group configuration.
+    ///
+    /// # Arguments
+    /// * index: sub-index into the group.
+    /// * config: configuration data for the interrupt source.
+    fn update(&self, _index: InterruptIndex, _config: InterruptSourceConfig) -> Result<()> {
+        // Interrupt source group update is a typical MSI
+        // related operation. Most legacy interrupts don't
+        // support that.
+        Ok(())
+    }
+
+    /// Mask an interrupt from this interrupt source group.
+    ///
+    /// # Arguments
+    /// * index: sub-index into the group.
+    fn mask(&self, _index: InterruptIndex) -> Result<()> {
+        // Not all interrupt sources can be disabled.
+        // To accommodate this, we can have a no-op here.
+        Ok(())
+    }
+
+    /// Unmask an interrupt from this interrupt source group.
+    ///
+    /// # Arguments
+    /// * index: sub-index into the group.
+    fn unmask(&self, _index: InterruptIndex) -> Result<()> {
+        // Not all interrupt sources can be disabled.
+        // To accommodate this, we can have a no-op here.
+        Ok(())
+    }
+}

src/lib.rs

@@ -6,6 +6,7 @@
 use std::cmp::{Ord, Ordering, PartialOrd};
 
 pub mod device_manager;
+pub mod interrupt;
 pub mod resources;
 
 // IO Size.