Add generic heplers to manage MSI interrupts

Introduce generic mechanism to support message signalled interrupts
based on KVM hypervisor.

Signed-off-by: Liu Jiang <gerry@linux.alibaba.com>
Signed-off-by: Bin Zha <zhabin@linux.alibaba.com>

Author: jiangliu

Cargo.toml

@@ -17,3 +17,4 @@ vm-memory = { git = "https://github.com/rust-vmm/vm-memory" }
 [features]
 kvm_irq = ["kvm-ioctls", "kvm-bindings"]
 legacy_irq = []
+msi_irq = []

src/interrupt/kvm/mod.rs

@@ -20,6 +20,9 @@ mod legacy_irq;
 #[cfg(feature = "legacy_irq")]
 use self::legacy_irq::LegacyIrq;
 
+#[cfg(feature = "msi_irq")]
+mod msi_irq;
+
 /// Structure to manage interrupt sources for a virtual machine based on the Linux KVM framework.
 ///
 /// The KVM framework provides methods to inject interrupts into the target virtual machines,

src/interrupt/kvm/msi_irq.rs

@@ -0,0 +1,59 @@
+// Copyright (C) 2019 Alibaba Cloud. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+//! Helper utilities for handling MSI interrupts.
+
+use super::*;
+use kvm_bindings::{kvm_irq_routing_entry, KVM_IRQ_ROUTING_MSI};
+
+pub(super) struct MsiConfig {
+    pub(super) irqfd: EventFd,
+    pub(super) config: Mutex<MsiIrqSourceConfig>,
+}
+
+impl MsiConfig {
+    pub(super) fn new() -> Self {
+        MsiConfig {
+            irqfd: EventFd::new(0).unwrap(),
+            config: Mutex::new(Default::default()),
+        }
+    }
+}
+
+pub(super) fn new_msi_routing_entry(
+    gsi: InterruptIndex,
+    msicfg: &MsiIrqSourceConfig,
+) -> kvm_irq_routing_entry {
+    let mut entry = kvm_irq_routing_entry {
+        gsi,
+        type_: KVM_IRQ_ROUTING_MSI,
+        flags: 0,
+        ..Default::default()
+    };
+    unsafe {
+        entry.u.msi.address_hi = msicfg.high_addr;
+        entry.u.msi.address_lo = msicfg.low_addr;
+        entry.u.msi.data = msicfg.data;
+    }
+    entry
+}
+
+#[allow(irrefutable_let_patterns)]
+pub(super) fn create_msi_routing_entries(
+    base: InterruptIndex,
+    configs: &[InterruptSourceConfig],
+) -> Result<Vec<kvm_irq_routing_entry>> {
+    let _ = base
+        .checked_add(configs.len() as u32)
+        .ok_or_else(|| std::io::Error::from_raw_os_error(libc::EINVAL))?;
+    let mut entries = Vec::with_capacity(configs.len());
+    for (i, ref val) in configs.iter().enumerate() {
+        if let InterruptSourceConfig::MsiIrq(msicfg) = val {
+            let entry = new_msi_routing_entry(base + i as u32, msicfg);
+            entries.push(entry);
+        } else {
+            return Err(std::io::Error::from_raw_os_error(libc::EINVAL));
+        }
+    }
+    Ok(entries)
+}