[PATCH net 1/2] ionic: add missing dma_rmb() after the completion publish check

[Eric Joyner <eric.joyner@amd.com>]

Each completion service routine tests a device-written publish flag and
then reads the rest of the descriptor with nothing ordering those loads.
A control dependency does not order loads, so a weakly ordered CPU may
satisfy the payload reads from a cache line state observed before the
flag became valid. Add the barrier to all four completion paths.

Fixes: 1d062b7b6f64 ("ionic: Add basic adminq support")
Fixes: 0f3154e6bcb3 ("ionic: Add Tx and Rx handling")
Fixes: 77ceb68e29cc ("ionic: Add notifyq support")
Assisted-by: Claude:claude-opus-5
Signed-off-by: Eric Joyner <eric.joyner@amd.com>
Reviewed-by: Brett Creeley <brett.creeley@amd.com>
---
 drivers/net/ethernet/pensando/ionic/ionic_main.c | 4 ++++
 drivers/net/ethernet/pensando/ionic/ionic_txrx.c | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/drivers/net/ethernet/pensando/ionic/ionic_main.c b/drivers/net/ethernet/pensando/ionic/ionic_main.c
index 6e6f3ed07271..10501be9ef95 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_main.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_main.c
@@ -269,6 +269,8 @@ bool ionic_notifyq_service(struct ionic_cq *cq)
 	if ((s64)(eid - lif->last_eid) <= 0)
 		return false;
 
+	dma_rmb();
+
 	lif->last_eid = eid;
 
 	dev_dbg(lif->ionic->dev, "notifyq event:\n");
@@ -314,6 +316,8 @@ bool ionic_adminq_service(struct ionic_cq *cq)
 	if (!color_match(comp->color, cq->done_color))
 		return false;
 
+	dma_rmb();
+
 	/* check for empty queue */
 	if (q->tail_idx == q->head_idx)
 		return false;
diff --git a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
index 301ebee2fdc5..5b58460350be 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
@@ -734,6 +734,8 @@ static bool __ionic_rx_service(struct ionic_cq *cq, struct bpf_prog *xdp_prog)
 	if (!color_match(comp->pkt_type_color, cq->done_color))
 		return false;
 
+	dma_rmb();
+
 	/* check for empty queue */
 	if (q->tail_idx == q->head_idx)
 		return false;
@@ -1249,6 +1251,8 @@ static bool ionic_tx_service(struct ionic_cq *cq,
 	if (!color_match(comp->color, cq->done_color))
 		return false;
 
+	dma_rmb();
+
 	/* clean the related q entries, there could be
 	 * several q entries completed for each cq completion
 	 */
-- 
2.43.0