Implement Drop for vfio_sys Device, unmapping msix for interrupts.

Cargo.lock

@@ -6949,6 +6949,7 @@ dependencies = [
  "bitfield-struct",
  "libc",
  "nix 0.26.4",
+ "pal_event",
  "tracing",
  "vfio-bindings",
 ]

vm/devices/user_driver/vfio_sys/Cargo.toml

@@ -11,6 +11,7 @@ libc.workspace = true
 nix = { workspace = true, features = ["ioctl"] }
 tracing.workspace = true
 vfio-bindings.workspace = true
+pal_event.workspace = true
 
 [lints]
 workspace = true

vm/devices/user_driver/vfio_sys/src/lib.rs

@@ -12,6 +12,7 @@ use std::fs;
 use std::fs::File;
 use std::io::BufRead;
 use std::io::BufReader;
+use std::iter;
 use std::os::unix::prelude::*;
 use std::path::Path;
 use vfio_bindings::bindings::vfio::vfio_device_info;
@@ -392,6 +393,17 @@ impl AsFd for Device {
     }
 }
 
+impl Drop for Device {
+    fn drop(&mut self) {
+        match self.map_msix(0, iter::empty::<pal_event::Event>()) {
+            Ok(_) => (),
+            Err(e) => {
+                tracing::error!("vfio_sys::Device::drop error calling map_msix: {:?}", e);
+            }
+        }
+    }
+}
+
 /// Find the Linux irq number for the MSI-X `index` of the PCI device `pci_id`.
 pub fn find_msix_irq(pci_id: &str, index: u32) -> anyhow::Result<u32> {
     let buffered = BufReader::new(File::open("/proc/interrupts")?);