On 7/14/26 5:59 AM, Simon Horman wrote:
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---
ibmveth: Add per-queue RX and TX statistics collection and reporting
This commit introduces per-queue statistics tracking for both receive and
transmit paths in the ibmveth driver. The counters are aggregated for legacy
interfaces and exposed individually via ethtool stringsets.
diff --git a/drivers/net/ethernet/ibm/ibmveth.c
b/drivers/net/ethernet/ibm/ibmveth.c
index 863e5c68b42c7..4e3f49b6346fd 100644
--- a/drivers/net/ethernet/ibm/ibmveth.c
+++ b/drivers/net/ethernet/ibm/ibmveth.c
[ ... ]
@@ -1655,6 +1655,10 @@ static int ibmveth_open(struct net_device *netdev)
if (rc)
goto out_cleanup_rx_interrupts;
+ rc = ibmveth_alloc_tx_qstats(adapter);
+ if (rc)
+ goto out_free_tx_resources;
+
netif_tx_start_all_queues(netdev);
netdev_dbg(netdev, "open complete\n");
[ ... ]
out_cleanup_rx_interrupts:
ibmveth_cleanup_rx_interrupts(adapter);
out_free_tx_resources:
ibmveth_free_tx_resources(adapter);
[Severity: High]
Does the goto out_free_tx_resources on ibmveth_alloc_tx_qstats() failure
bypass the cleanup for RX interrupts?
Since out_free_tx_resources is physically below out_cleanup_rx_interrupts in
ibmveth_open(), failing here leaves the IRQs requested and NAPI enabled. If
an interrupt subsequently fires, could the handler access the freed RX queue
memory and cause a kernel panic?
[ ... ]
*
Confirmed — that goto skips RX interrupt cleanup. Will fix the
open() unwind order in v4 so TX-stat allocation failure still
disables NAPI and frees IRQs before tearing down queues.
*
@@ -1699,6 +1699,7 @@ static int ibmveth_close(struct net_device *netdev)
}
}
+ ibmveth_free_tx_qstats(adapter);
ibmveth_free_tx_resources(adapter);
ibmveth_cleanup_rx_interrupts(adapter);
ibmveth_update_rx_no_buffer(adapter);
[ ... ]
ibmveth_free_rx_qstats(adapter);
[Severity: High]
If ibmveth_close() is called to bring down the interface, does this
unconditionally free adapter->tx_qstats and adapter->rx_qstats without a
grace period?
Confirmed.
Since ibmveth_get_stats64() can be called concurrently under RCU, and
ibmveth_start_xmit() can run concurrently if the datapath is not completely
synchronized, could this lead to a use-after-free or NULL pointer dereference
when these functions access the freed arrays?
[ ... ]
*
Good point. ndo_get_stats64 can run without RTNL. In v4 I’ll give
the qstat arrays adapter lifetime (probe/remove) instead of
open/close, so close cannot free them under concurrent readers.
*
@@ -1967,22 +1967,107 @@ static int ibmveth_set_features(struct net_device *dev,
[ ... ]
+static void ibmveth_aggregate_rx_qstats(struct ibmveth_adapter *adapter)
+{
+ u64 total_invalid = 0;
+ u64 total_large = 0;
+ int i;
+
+ if (!adapter->rx_qstats)
+ return;
+
+ for (i = 0; i < adapter->num_rx_queues; i++) {
+ total_invalid += adapter->rx_qstats[i].invalid_buffers;
+ total_large += adapter->rx_qstats[i].large_packets;
+ }
+
+ adapter->rx_invalid_buffer = total_invalid;
+ adapter->rx_large_packets = total_large;
+}
[Severity: High]
Does overwriting adapter->rx_invalid_buffer and other persistent global
counters with the dynamically allocated adapter->rx_qstats values cause a
permanent loss of interface statistics?
yes
When the interface is brought down and back up, ibmveth_close() frees the
queue stats arrays and ibmveth_open() reallocates them as zeroed. Will this
cause all historical statistics to be wiped out on every interface reset,
breaking standard persistence behavior?
[ ... ]
*
Agreed this regresses persistence vs pre-MQ.
**
In v4 per-queue qstats will stay for the adapter lifetime, and adapter-level
ethtool strings are summed on read (ibmvnic-style). No dual-updating
globals on the hot path, and no aggregate_* that wipes history on reopen.
*
+static void ibmveth_get_strings(struct net_device *dev, u32 stringset, u8
*data)
+{
[ ... ]
+ for (i = 0; i < adapter->num_rx_queues; i++) {
+ ethtool_sprintf(&p, "rx%d_packets", i);
+ ethtool_sprintf(&p, "rx%d_bytes", i);
[Severity: Low]
Are these private ethtool stringsets duplicating standard kernel statistics?
According to the subsystem guidelines, per-queue packet and byte statistics
that have a standard UAPI representation (like struct netdev_queue_stats_rx
exported via netlink) should not be duplicated as private ethtool strings.
*
Thanks — **
*I can move those to standard*
*
netdev queue stats and drop the ethtool duplicates in a follow-up. For
now I'll keep device-specific counters (interrupts, polls, invalid, …)
as private ethtool strings.
*
*
diff --git a/drivers/net/ethernet/ibm/ibmveth.h
b/drivers/net/ethernet/ibm/ibmveth.h
index f7b20fd01acb5..390c660af979e 100644
--- a/drivers/net/ethernet/ibm/ibmveth.h
+++ b/drivers/net/ethernet/ibm/ibmveth.h
@@ -316,9 +316,21 @@ struct ibmveth_rx_queue_stats {
u64 no_buffer_drops;
};
+struct ibmveth_tx_queue_stats {
+ u64 packets;
+ u64 bytes;
+ u64 large_packets;
+ u64 dropped_packets;
+ u64 send_failures;
+ u64 checksum_offload;
+};
[Severity: Medium]
Will this structure layout prevent cache line false sharing?
The commit message mentions tracking transmit counters per TX queue to avoid
cache line contention, but struct ibmveth_tx_queue_stats appears to be
exactly 48 bytes and lacks cacheline alignment annotations like
____cacheline_aligned. When allocated as a contiguous array, will multiple
CPUs processing different queues end up writing to the same hardware
cacheline?
*Will add cacheline alignment for the per-queue stats structs in v4*
*Thanks again for your valuable feedback!*
*Mingming*
