[PATCH net 2/5] eth: bnxt: resize Rx head buffers when rx-copybreak changes

[Jakub Kicinski <kuba@kernel.org>]

Since rx-copybreak became configurable, bnxt_set_ring_params() sizes
the head buffers to fit at least rx_copybreak bytes, and the copybreak
path in bnxt_copy_data() syncs rx_copybreak bytes of the head buffer.
bnxt_set_tunable() however only updates bp->rx_copybreak, and nothing
on the open path recalculates the ring parameters. After raising
rx-copybreak the head buffers keep their old size until some other
setting changes, and bnxt_copy_data() syncs past their end, into the
next buffer in the page or past the end of the page:

  DMA-API: bnxt_en 0000:01:00.0: device driver tries to sync DMA memory it has not allocated [device address=0x00000002aa210c40] [size=1024 bytes]
  WARNING: kernel/dma/debug.c:1162 at check_sync+0x577/0x1eb0, CPU#22: swapper/22/0
  Call Trace:
   <IRQ>
   debug_dma_sync_single_for_cpu+0x66/0x90
   bnxt_copy_data+0x12f/0x290
   bnxt_rx_pkt+0x24ea/0x50f0
   __bnxt_poll_work+0x42c/0xc00
   bnxt_poll_p5+0x579/0x17a0
   __napi_poll+0x8b/0x2c0
   net_rx_action+0x58f/0xbb0

Here the head buffers were still sized for the 640B HDS threshold,
four 1kB buffers per page, while rx-copybreak was raised to 1024.
Without coherent DMA or with swiotlb the oversized sync can corrupt
a neighboring buffer owned by the device or by an skb.

The device must be down for rx-copybreak to change, so recalculate the
ring parameters right away, like bnxt_set_ringparam() does.

Hit while testing patch 1, tested on BCM57504 - boot; set rx-copybreak
to 1024 with the link down (CONFIG_DMA_API_DEBUG); ifup.

Fixes: 152f4da05aee ("bnxt_en: add support for rx-copybreak ethtool command")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
index 622e89587e5d..ef4bea4a0f8c 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
@@ -4601,6 +4601,7 @@ static int bnxt_set_tunable(struct net_device *dev,
 			if (netif_running(dev))
 				return -EBUSY;
 			bp->rx_copybreak = rx_copybreak;
+			bnxt_set_ring_params(bp);
 		}
 		return 0;
 	case ETHTOOL_PFC_PREVENTION_TOUT:
-- 
2.56.0