refactor: use vmm_sys_util::timer module instead of timefd crate

Use vmm_sys_util's timerfd implementation instead of the one in the
timerfd crate. This eliminates a couple of dependencies, including an
aesthetically unpleasing double-dependency on different versions of
rustix.

Signed-off-by: Patrick Roy <roypat@amazon.co.uk>

Author: roypat

Cargo.lock

@@ -41,3 +41,6 @@ strip = "none"
 
 [profile.bench]
 strip = "debuginfo"
+
+[patch.crates-io]
+vmm-sys-util = { git = "https://github.com/roypat/vmm-sys-util", branch = "timerfd-nonblock-0.14" }

Cargo.toml

@@ -29,7 +29,6 @@ serde = { version = "1.0.219", features = ["derive"] }
 serde_derive = "1.0.136"
 serde_json = "1.0.143"
 thiserror = "2.0.16"
-timerfd = "1.6.0"
 utils = { path = "../utils" }
 vmm = { path = "../vmm" }
 vmm-sys-util = { version = "0.14.0", features = ["with-serde"] }

src/firecracker/Cargo.toml

@@ -5,9 +5,9 @@ use std::os::unix::io::AsRawFd;
 use std::time::Duration;
 
 use event_manager::{EventOps, Events, MutEventSubscriber};
-use timerfd::{ClockId, SetTimeFlags, TimerFd, TimerState};
 use vmm::logger::{IncMetric, METRICS, error, warn};
 use vmm_sys_util::epoll::EventSet;
+use vmm_sys_util::timerfd::{TimerFd, TimerFdFlag};
 
 /// Metrics reporting period.
 pub(crate) const WRITE_METRICS_PERIOD_MS: u64 = 60000;
@@ -23,7 +23,7 @@ pub(crate) struct PeriodicMetrics {
 impl PeriodicMetrics {
     /// PeriodicMetrics constructor. Can panic on `TimerFd` creation failure.
     pub fn new() -> Self {
-        let write_metrics_event_fd = TimerFd::new_custom(ClockId::Monotonic, true, true)
+        let write_metrics_event_fd = TimerFd::new_with_flags(TimerFdFlag::NONBLOCK)
             .expect("Cannot create the metrics timer fd.");
         PeriodicMetrics {
             write_metrics_event_fd,
@@ -35,12 +35,10 @@ impl PeriodicMetrics {
     /// Start the periodic metrics engine which will flush metrics every `interval_ms` millisecs.
     pub(crate) fn start(&mut self, interval_ms: u64) {
         // Arm the log write timer.
-        let timer_state = TimerState::Periodic {
-            current: Duration::from_millis(interval_ms),
-            interval: Duration::from_millis(interval_ms),
-        };
+        let duration = Duration::from_millis(interval_ms);
         self.write_metrics_event_fd
-            .set_state(timer_state, SetTimeFlags::Default);
+            .reset(duration, Some(duration))
+            .expect("failed to arm metrics write timer");
 
         // Write the metrics straight away to check the process startup time.
         self.write_metrics();
@@ -77,7 +75,9 @@ impl MutEventSubscriber for PeriodicMetrics {
         }
 
         if source == self.write_metrics_event_fd.as_raw_fd() {
-            self.write_metrics_event_fd.read();
+            self.write_metrics_event_fd
+                .wait()
+                .expect("failed to read metrics timer");
             self.write_metrics();
         } else {
             error!("Spurious METRICS event!");

src/firecracker/src/metrics.rs

@@ -47,7 +47,6 @@ serde = { version = "1.0.219", features = ["derive", "rc"] }
 serde_json = "1.0.143"
 slab = "0.4.11"
 thiserror = "2.0.16"
-timerfd = "1.5.0"
 userfaultfd = "0.9.0"
 utils = { path = "../utils" }
 uuid = "1.18.0"

src/vmm/Cargo.toml

@@ -7,8 +7,8 @@ use std::time::Duration;
 
 use log::{error, info};
 use serde::Serialize;
-use timerfd::{ClockId, SetTimeFlags, TimerFd, TimerState};
 use vmm_sys_util::eventfd::EventFd;
+use vmm_sys_util::timerfd::{TimerFd, TimerFdFlag};
 
 use super::super::ActivateError;
 use super::super::device::{DeviceState, VirtioDevice};
@@ -215,7 +215,7 @@ impl Balloon {
         }
 
         let stats_timer =
-            TimerFd::new_custom(ClockId::Monotonic, true, true).map_err(BalloonError::Timer)?;
+            TimerFd::new_with_flags(TimerFdFlag::NONBLOCK).map_err(BalloonError::Timer)?;
 
         Ok(Balloon {
             avail_features,
@@ -259,7 +259,7 @@ impl Balloon {
     }
 
     pub(crate) fn process_stats_timer_event(&mut self) -> Result<(), BalloonError> {
-        self.stats_timer.read();
+        self.stats_timer.wait()?;
         self.trigger_stats_update()
     }
 
@@ -486,12 +486,8 @@ impl Balloon {
     }
 
     pub fn update_timer_state(&mut self) {
-        let timer_state = TimerState::Periodic {
-            current: Duration::from_secs(u64::from(self.stats_polling_interval_s)),
-            interval: Duration::from_secs(u64::from(self.stats_polling_interval_s)),
-        };
-        self.stats_timer
-            .set_state(timer_state, SetTimeFlags::Default);
+        let duration = Duration::from_secs(self.stats_polling_interval_s as u64);
+        self.stats_timer.reset(duration, Some(duration));
     }
 
     /// Obtain the number of 4K pages the device is currently holding.

src/vmm/src/devices/virtio/balloon/device.rs

@@ -90,7 +90,7 @@ pub enum BalloonError {
     /// {0}
     InvalidAvailIdx(#[from] InvalidAvailIdx),
     /// Error creating the statistics timer: {0}
-    Timer(std::io::Error),
+    Timer(#[from] vmm_sys_util::errno::Error),
 }
 
 #[derive(Debug, thiserror::Error, displaydoc::Display)]

src/vmm/src/devices/virtio/balloon/mod.rs

@@ -7,7 +7,6 @@ use std::sync::Arc;
 use std::time::Duration;
 
 use serde::{Deserialize, Serialize};
-use timerfd::{SetTimeFlags, TimerState};
 
 use super::*;
 use crate::devices::virtio::balloon::device::{BalloonStats, ConfigSpace};
@@ -157,13 +156,8 @@ impl Persist<'_> for Balloon {
             balloon.set_stats_desc_index(state.stats_desc_index);
 
             // Restart timer if needed.
-            let timer_state = TimerState::Periodic {
-                current: Duration::from_secs(u64::from(state.stats_polling_interval_s)),
-                interval: Duration::from_secs(u64::from(state.stats_polling_interval_s)),
-            };
-            balloon
-                .stats_timer
-                .set_state(timer_state, SetTimeFlags::Default);
+            let duration = Duration::from_secs(state.stats_polling_interval_s as u64);
+            balloon.stats_timer.reset(duration, Some(duration));
         }
 
         Ok(balloon)

src/vmm/src/devices/virtio/balloon/persist.rs

@@ -5,7 +5,7 @@ use std::os::unix::io::{AsRawFd, RawFd};
 use std::time::{Duration, Instant};
 use std::{fmt, io};
 
-use timerfd::{ClockId, SetTimeFlags, TimerFd, TimerState};
+use vmm_sys_util::timerfd::{TimerFd, TimerFdFlag};
 
 pub mod persist;
 
@@ -14,12 +14,12 @@ pub mod persist;
 pub enum RateLimiterError {
     /// Rate limiter event handler called without a present timer
     SpuriousRateLimiterEvent,
+    /// Error reading timerfd: {0}
+    Read(#[from] vmm_sys_util::errno::Error),
 }
 
 // Interval at which the refill timer will run when limiter is at capacity.
-const REFILL_TIMER_INTERVAL_MS: u64 = 100;
-const TIMER_REFILL_STATE: TimerState =
-    TimerState::Oneshot(Duration::from_millis(REFILL_TIMER_INTERVAL_MS));
+const REFILL_TIMER_DURATION: Duration = Duration::from_millis(100);
 
 const NANOSEC_IN_ONE_MILLISEC: u64 = 1_000_000;
 
@@ -367,7 +367,7 @@ impl RateLimiter {
         // We'll need a timer_fd, even if our current config effectively disables rate limiting,
         // because `Self::update_buckets()` might re-enable it later, and we might be
         // seccomp-blocked from creating the timer_fd at that time.
-        let timer_fd = TimerFd::new_custom(ClockId::Monotonic, true, true)?;
+        let timer_fd = TimerFd::new_with_flags(TimerFdFlag::NONBLOCK)?;
 
         Ok(RateLimiter {
             bandwidth: bytes_token_bucket,
@@ -378,9 +378,11 @@ impl RateLimiter {
     }
 
     // Arm the timer of the rate limiter with the provided `TimerState`.
-    fn activate_timer(&mut self, timer_state: TimerState) {
+    fn activate_timer(&mut self, one_shot_duration: Duration) {
         // Register the timer; don't care about its previous state
-        self.timer_fd.set_state(timer_state, SetTimeFlags::Default);
+        self.timer_fd
+            .reset(one_shot_duration, None)
+            .expect("failed to activate ratelimiter timer");
         self.timer_active = true;
     }
 
@@ -407,7 +409,7 @@ impl RateLimiter {
                 // make sure there is only one running timer for this limiter.
                 BucketReduction::Failure => {
                     if !self.timer_active {
-                        self.activate_timer(TIMER_REFILL_STATE);
+                        self.activate_timer(REFILL_TIMER_DURATION);
                     }
                     false
                 }
@@ -424,9 +426,7 @@ impl RateLimiter {
                     // `ratio * refill_time` milliseconds.
                     // The conversion should be safe because the ratio is positive.
                     #[allow(clippy::cast_sign_loss, clippy::cast_possible_truncation)]
-                    self.activate_timer(TimerState::Oneshot(Duration::from_millis(
-                        (ratio * refill_time as f64) as u64,
-                    )));
+                    self.activate_timer(Duration::from_millis((ratio * refill_time as f64) as u64));
                     true
                 }
             }
@@ -469,7 +469,7 @@ impl RateLimiter {
     ///
     /// If the rate limiter is disabled or is not blocked, an error is returned.
     pub fn event_handler(&mut self) -> Result<(), RateLimiterError> {
-        match self.timer_fd.read() {
+        match self.timer_fd.wait()? {
             0 => Err(RateLimiterError::SpuriousRateLimiterEvent),
             _ => {
                 self.timer_active = false;
@@ -777,7 +777,7 @@ pub(crate) mod tests {
     // second wait will always result in the limiter being refilled. Otherwise
     // there is a chance for a race condition between limiter refilling and limiter
     // checking.
-    const TEST_REFILL_TIMER_INTERVAL_MS: u64 = REFILL_TIMER_INTERVAL_MS + 10;
+    const TEST_REFILL_TIMER_DURATION: Duration = Duration::from_millis(110);
 
     impl TokenBucket {
         // Resets the token bucket: budget set to max capacity and last-updated set to now.
@@ -1014,11 +1014,11 @@ pub(crate) mod tests {
         // since consume failed, limiter should be blocked now
         assert!(l.is_blocked());
         // wait half the timer period
-        thread::sleep(Duration::from_millis(TEST_REFILL_TIMER_INTERVAL_MS / 2));
+        thread::sleep(TEST_REFILL_TIMER_DURATION / 2);
         // limiter should still be blocked
         assert!(l.is_blocked());
         // wait the other half of the timer period
-        thread::sleep(Duration::from_millis(TEST_REFILL_TIMER_INTERVAL_MS / 2));
+        thread::sleep(TEST_REFILL_TIMER_DURATION / 2);
         // the timer_fd should have an event on it by now
         l.event_handler().unwrap();
         // limiter should now be unblocked
@@ -1047,11 +1047,11 @@ pub(crate) mod tests {
         // since consume failed, limiter should be blocked now
         assert!(l.is_blocked());
         // wait half the timer period
-        thread::sleep(Duration::from_millis(TEST_REFILL_TIMER_INTERVAL_MS / 2));
+        thread::sleep(TEST_REFILL_TIMER_DURATION / 2);
         // limiter should still be blocked
         assert!(l.is_blocked());
         // wait the other half of the timer period
-        thread::sleep(Duration::from_millis(TEST_REFILL_TIMER_INTERVAL_MS / 2));
+        thread::sleep(TEST_REFILL_TIMER_DURATION / 2);
         // the timer_fd should have an event on it by now
         l.event_handler().unwrap();
         // limiter should now be unblocked
@@ -1081,11 +1081,11 @@ pub(crate) mod tests {
         // since consume failed, limiter should be blocked now
         assert!(l.is_blocked());
         // wait half the timer period
-        thread::sleep(Duration::from_millis(TEST_REFILL_TIMER_INTERVAL_MS / 2));
+        thread::sleep(TEST_REFILL_TIMER_DURATION / 2);
         // limiter should still be blocked
         assert!(l.is_blocked());
         // wait the other half of the timer period
-        thread::sleep(Duration::from_millis(TEST_REFILL_TIMER_INTERVAL_MS / 2));
+        thread::sleep(TEST_REFILL_TIMER_DURATION / 2);
         // the timer_fd should have an event on it by now
         l.event_handler().unwrap();
         // limiter should now be unblocked

src/vmm/src/rate_limiter/mod.rs

@@ -4,6 +4,7 @@
 //! Defines the structures needed for saving/restoring a RateLimiter.
 
 use serde::{Deserialize, Serialize};
+use vmm_sys_util::timerfd::{TimerFd, TimerFdFlag};
 
 use super::*;
 use crate::snapshot::Persist;
@@ -82,7 +83,7 @@ impl Persist<'_> for RateLimiter {
             } else {
                 None
             },
-            timer_fd: TimerFd::new_custom(ClockId::Monotonic, true, true)?,
+            timer_fd: TimerFd::new_with_flags(TimerFdFlag::NONBLOCK)?,
             timer_active: false,
         };
 
@@ -151,10 +152,7 @@ mod tests {
                 .unwrap()
                 .partial_eq(restored_rate_limiter.bandwidth().unwrap())
         );
-        assert_eq!(
-            restored_rate_limiter.timer_fd.get_state(),
-            TimerState::Disarmed
-        );
+        assert!(!restored_rate_limiter.timer_fd.is_armed().unwrap());
 
         // Check that RateLimiter restores correctly after partially consuming tokens.
         rate_limiter.consume(10, TokenType::Bytes);
@@ -174,10 +172,7 @@ mod tests {
                 .unwrap()
                 .partial_eq(restored_rate_limiter.bandwidth().unwrap())
         );
-        assert_eq!(
-            restored_rate_limiter.timer_fd.get_state(),
-            TimerState::Disarmed
-        );
+        assert!(!restored_rate_limiter.timer_fd.is_armed().unwrap());
 
         // Check that RateLimiter restores correctly after totally consuming tokens.
         rate_limiter.consume(1000, TokenType::Bytes);