6.17-stable review patch. If anyone has any objections, please let me know.
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From: Mohammad Heib mheib@redhat.com
[ Upstream commit d261f5b09c28850dc63ca1d3018596f829f402d5 ]
The TX path currently writes descriptors and then immediately writes to the MMIO doorbell register to notify the NIC. On weakly ordered architectures, descriptor writes may still be pending in CPU or DMA write buffers when the doorbell is issued, leading to the device fetching stale or incomplete descriptors.
Add a dma_wmb() in ionic_txq_post() to ensure all descriptor writes are visible to the device before the doorbell MMIO write.
Fixes: 0f3154e6bcb3 ("ionic: Add Tx and Rx handling") Signed-off-by: Mohammad Heib mheib@redhat.com Link: https://patch.msgid.link/20251031155203.203031-1-mheib@redhat.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/pensando/ionic/ionic_txrx.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c index d10b58ebf6034..2e571d0a0d8a2 100644 --- a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c +++ b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c @@ -29,6 +29,10 @@ static void ionic_tx_clean(struct ionic_queue *q,
static inline void ionic_txq_post(struct ionic_queue *q, bool ring_dbell) { + /* Ensure TX descriptor writes reach memory before NIC reads them. + * Prevents device from fetching stale descriptors. + */ + dma_wmb(); ionic_q_post(q, ring_dbell); }