Add try_from/unwrap for u128 time values

Some of Rust's time measurements use u128 for outputs but u64 for
inputs. I don't expect we'll overflow a u64 - 2^64 nanoseconds is over
500 years - so I've added try_from()/unwrap() calls to those
conversions.

Signed-off-by: Jonathan Browne <[email protected]>

Author: JBYoshi

src/vmm/src/rate_limiter/mod.rs

@@ -417,7 +417,8 @@ impl RateLimiter {
                     // order to enforce the bandwidth limit we need to prevent
                     // further calls to the rate limiter for
                     // `ratio * refill_time` milliseconds.
-                    #[allow(clippy::cast_sign_loss)] // ratio is always positive
+                    // 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,
                     )));

src/vmm/src/rate_limiter/persist.rs

@@ -31,7 +31,8 @@ impl Persist<'_> for TokenBucket {
             one_time_burst: self.one_time_burst,
             refill_time: self.refill_time,
             budget: self.budget,
-            elapsed_ns: self.last_update.elapsed().as_nanos() as u64,
+            // This should be safe for a duration of about 584 years.
+            elapsed_ns: u64::try_from(self.last_update.elapsed().as_nanos()).unwrap(),
         }
     }