feat(balloon): add logging for malformed balloon-stats tag

Added warn logging to the decode of BalloonStats if unknown tag is
introduced. Additionally, updated integration test of BalloonStats to
fail if this warn occurs.

Signed-off-by: Aaron Lo <[email protected]>

Author: 22aronl

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

@@ -5,7 +5,7 @@ use std::ops::Deref;
 use std::sync::Arc;
 use std::time::Duration;
 
-use log::{error, info, warn};
+use log::{debug, error, info, warn};
 use serde::{Deserialize, Serialize};
 use utils::time::TimerFd;
 use vmm_sys_util::eventfd::EventFd;
@@ -207,7 +207,7 @@ pub struct BalloonStats {
 }
 
 impl BalloonStats {
-    fn update_with_stat(&mut self, stat: &BalloonStat) -> Result<(), BalloonError> {
+    fn update_with_stat(&mut self, stat: &BalloonStat) {
         let val = Some(stat.val);
         match stat.tag {
             VIRTIO_BALLOON_S_SWAP_IN => self.swap_in = val,
@@ -226,12 +226,11 @@ impl BalloonStats {
             VIRTIO_BALLOON_S_DIRECT_SCAN => self.direct_scan = val,
             VIRTIO_BALLOON_S_ASYNC_RECLAIM => self.async_reclaim = val,
             VIRTIO_BALLOON_S_DIRECT_RECLAIM => self.direct_reclaim = val,
-            _ => {
-                return Err(BalloonError::MalformedPayload);
+            tag => {
+                METRICS.stats_update_fails.inc();
+                debug!("balloon: unknown stats update tag: {tag}");
             }
         }
-
-        Ok(())
     }
 }
 
@@ -503,10 +502,7 @@ impl Balloon {
                 let stat = mem
                     .read_obj::<BalloonStat>(addr)
                     .map_err(|_| BalloonError::MalformedDescriptor)?;
-                self.latest_stats.update_with_stat(&stat).map_err(|_| {
-                    METRICS.stats_update_fails.inc();
-                    BalloonError::MalformedPayload
-                })?;
+                self.latest_stats.update_with_stat(&stat);
             }
 
             self.stats_desc_index = Some(head.index);
@@ -1067,52 +1063,52 @@ pub(crate) mod tests {
             val: 1,
         };
 
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.swap_in, Some(1));
         stat.tag = VIRTIO_BALLOON_S_SWAP_OUT;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.swap_out, Some(1));
         stat.tag = VIRTIO_BALLOON_S_MAJFLT;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.major_faults, Some(1));
         stat.tag = VIRTIO_BALLOON_S_MINFLT;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.minor_faults, Some(1));
         stat.tag = VIRTIO_BALLOON_S_MEMFREE;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.free_memory, Some(1));
         stat.tag = VIRTIO_BALLOON_S_MEMTOT;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.total_memory, Some(1));
         stat.tag = VIRTIO_BALLOON_S_AVAIL;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.available_memory, Some(1));
         stat.tag = VIRTIO_BALLOON_S_CACHES;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.disk_caches, Some(1));
         stat.tag = VIRTIO_BALLOON_S_HTLB_PGALLOC;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.hugetlb_allocations, Some(1));
         stat.tag = VIRTIO_BALLOON_S_HTLB_PGFAIL;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.hugetlb_failures, Some(1));
         stat.tag = VIRTIO_BALLOON_S_OOM_KILL;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.oom_kill, Some(1));
         stat.tag = VIRTIO_BALLOON_S_ALLOC_STALL;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.alloc_stall, Some(1));
         stat.tag = VIRTIO_BALLOON_S_ASYNC_SCAN;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.async_scan, Some(1));
         stat.tag = VIRTIO_BALLOON_S_DIRECT_SCAN;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.direct_scan, Some(1));
         stat.tag = VIRTIO_BALLOON_S_ASYNC_RECLAIM;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.async_reclaim, Some(1));
         stat.tag = VIRTIO_BALLOON_S_DIRECT_RECLAIM;
-        stats.update_with_stat(&stat).unwrap();
+        stats.update_with_stat(&stat);
         assert_eq!(stats.direct_reclaim, Some(1));
     }
 

tests/integration_tests/functional/test_balloon.py

@@ -320,6 +320,9 @@ def test_stats(uvm_plain_any):
     # Get another reading of the stats after the polling interval has passed.
     deflated_stats = test_microvm.api.balloon_stats.get().json()
 
+    # Ensure that stats don't have unknown balloon stats fields
+    assert "balloon: unknown stats update tag:" not in test_microvm.log_data
+
     # Ensure the stats reflect deflating the balloon.
     assert inflated_stats["free_memory"] < deflated_stats["free_memory"]
     assert inflated_stats["available_memory"] < deflated_stats["available_memory"]
@@ -372,6 +375,9 @@ def test_stats_update(uvm_plain_any):
     final_stats = test_microvm.api.balloon_stats.get().json()
     assert next_stats["available_memory"] != final_stats["available_memory"]
 
+    # Ensure that stats don't have unknown balloon stats fields
+    assert "balloon: unknown stats update tag:" not in test_microvm.log_data
+
 
 def test_balloon_snapshot(uvm_plain_any, microvm_factory):
     """