[RFC net v2 3/3] bnxt_en: stop DMA before releasing rings the firmware did not free

[Joe Damato <joe@dama.to>]

When HWRM_RING_FREE is not answered, bnxt_hwrm_ring_free() clears
fw_ring_id and __bnxt_close_nic() goes on to call bnxt_free_mem(), which
unmaps the ring memory and the RX buffers that the FW may still be
using.

This is reachable in production. On a BCM57504 the first sign is the TX
watchdog; the close that follows times out a subset of its RING_FREEs and
the driver releases those rings anyway:

  05:30:12  NETDEV WATCHDOG: transmit queue 0 timed out 6073 ms
  05:30:12  Resp cmpl intr err msg: 0x51                  x20
  05:30:12  hwrm_ring_free type 1 failed                  x12
  05:30:12  hwrm_ring_free type 2 failed                  x8
  05:30:12  AMD-Vi: IO_PAGE_FAULT  x3

Count the rings the firmware did not free and, if there are any, disable
the device before the close path releases memory.

The device stays unusable until a firmware reset.

Fixes: 74608fc98d28 ("bnxt_en: Ring free response from close path should use completion ring")
Signed-off-by: Joe Damato <joe@dama.to>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index a7f6facca7b4..574532d7047b 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -7756,6 +7756,7 @@ static void bnxt_clear_one_cp_ring(struct bnxt *bp, struct bnxt_cp_ring_info *cp
 
 static void bnxt_hwrm_ring_free(struct bnxt *bp, bool close_path)
 {
+	int stuck = 0;
 	u32 type;
 	int i;
 
@@ -7763,12 +7764,15 @@ static void bnxt_hwrm_ring_free(struct bnxt *bp, bool close_path)
 		return;
 
 	for (i = 0; i < bp->tx_nr_rings; i++)
-		bnxt_hwrm_tx_ring_free(bp, &bp->tx_ring[i], close_path);
+		if (bnxt_hwrm_tx_ring_free(bp, &bp->tx_ring[i], close_path))
+			stuck++;
 
 	bnxt_cancel_dim(bp);
 	for (i = 0; i < bp->rx_nr_rings; i++) {
-		bnxt_hwrm_rx_ring_free(bp, &bp->rx_ring[i], close_path);
-		bnxt_hwrm_rx_agg_ring_free(bp, &bp->rx_ring[i], close_path);
+		if (bnxt_hwrm_rx_ring_free(bp, &bp->rx_ring[i], close_path))
+			stuck++;
+		if (bnxt_hwrm_rx_agg_ring_free(bp, &bp->rx_ring[i], close_path))
+			stuck++;
 	}
 
 	/* The completion rings are about to be freed.  After that the
@@ -7798,6 +7802,17 @@ static void bnxt_hwrm_ring_free(struct bnxt *bp, bool close_path)
 			bp->grp_info[i].cp_fw_ring_id = INVALID_HW_RING_ID;
 		}
 	}
+
+	if (!stuck)
+		return;
+
+	/* FW never acknowledged freeing these rings, so it may still be
+	 * DMAing to them. Stop the device before handing memory back.
+	 */
+	netdev_err(bp->dev,
+		   "Firmware did not free %d ring(s); disabling DMA before releasing ring memory. A firmware reset is required.\n",
+		   stuck);
+	pci_disable_device(bp->pdev);
 }
 
 static int __bnxt_trim_rings(struct bnxt *bp, int *rx, int *tx, int max,
-- 
2.53.0-Meta