[PATCH net-next v7 12/15] ibmveth: Report MQ-aware RX counts in ethtool get_channels

[Mingming Cao <mmc@linux.ibm.com>]

Report MQ-aware channel limits and counts from get_channels():

  - max_rx is IBMVETH_MAX_RX_QUEUES when MQ firmware is enabled, else 1
  - rx_count tracks the driver's published num_rx_queues

Previously get_channels() mirrored netdev->real_num_rx_queues for both
fields, which under-reports max_rx on MQ firmware and can disagree with
the driver's private RX count before the next open.

This patch only reports. set_channels() still only adjusts tx_count, so
an RX channel request returns -EOPNOTSUPP if rx_count changes, while
read-modify-write TX requests pass through with the live rx_count.
Patch 14 implements live RX resizing via ibmveth_resize_rx_channels(),
and patch 15 completes the down-path publish/rollback and caps max_rx
once mq_fallback latches.

Keep this out of the stats patch: channel reporting is ethtool -l ABI,
independent of per-queue counters, so it can be reviewed and blamed on
its own.

Signed-off-by: Mingming Cao <mmc@linux.ibm.com>
Reviewed-by: Dave Marquardt <davemarq@linux.ibm.com>
Tested-by: Shaik Abdulla <shaik.abdulla1@ibm.com>
---

Changes in v7:
- reject rx_count change with -EOPNOTSUPP in
  set_channels() until patch 14 implements resize
- noted: TX-only read-modify-write still passes;
  max_rx stays here (reject, not reorder);
  get_channels uses the adapter count,
  get_base_stats uses real_num; RX max is
  MAX_RX_QUEUES, not the TX CPU cap; P14
  wires live rx_count resize; P15 is the
  tip ABI (live rx_count, max_rx cap on
  mq_fallback, max_tx at least the live tx_count)

Changes in v5:
- get_channels rx_count via get_num_rx_queues() (READ_ONCE consistency)
- New peel: get_channels from v4 stats -> tip P12 (14->15)
- get_channels: max_rx = MAX_RX_QUEUES when MQ else 1; rx_count =
  get_num_rx_queues() (was mirroring real_num_rx_queues for both)

 drivers/net/ethernet/ibm/ibmveth.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
index 2575a7c11afb..cd2e5e4a81fe 100644
--- a/drivers/net/ethernet/ibm/ibmveth.c
+++ b/drivers/net/ethernet/ibm/ibmveth.c
@@ -2546,11 +2546,16 @@ static void ibmveth_get_ethtool_stats(struct net_device *dev,
 static void ibmveth_get_channels(struct net_device *netdev,
 				 struct ethtool_channels *channels)
 {
+	struct ibmveth_adapter *adapter = netdev_priv(netdev);
+
 	channels->max_tx = ibmveth_real_max_tx_queues();
 	channels->tx_count = netdev->real_num_tx_queues;
 
-	channels->max_rx = netdev->real_num_rx_queues;
-	channels->rx_count = netdev->real_num_rx_queues;
+	if (adapter->multi_queue)
+		channels->max_rx = IBMVETH_MAX_RX_QUEUES;
+	else
+		channels->max_rx = 1;
+	channels->rx_count = ibmveth_get_num_rx_queues(adapter);
 }
 
 static int ibmveth_set_channels(struct net_device *netdev,
@@ -2561,6 +2566,14 @@ static int ibmveth_set_channels(struct net_device *netdev,
 		     goal = channels->tx_count;
 	int rc, i;
 
+	/*
+	 * RX channel resize is implemented in a later patch; reject any
+	 * request that changes rx_count. Read-modify-write TX adjustments
+	 * submit the current rx_count and proceed.
+	 */
+	if (channels->rx_count != ibmveth_get_num_rx_queues(adapter))
+		return -EOPNOTSUPP;
+
 	/* If ndo_open has not been called yet then don't allocate, just set
 	 * desired netdev_queue's and return
 	 */
-- 
2.50.1 (Apple Git-155)