[PATCH 5.2 37/85] ixgbe: fix double clean of Tx descriptors with xdp

Greg Kroah-Hartman
2019-09-18T06:25:41Z

From: Ilya Maximets <i.maximets@samsung.com>

commit bf280c0387ebbf8eebad1036fca8f7b85ebfde32 upstream.

Tx code doesn't clear the descriptors' status after cleaning.
So, if the budget is larger than number of used elems in a ring, some
descriptors will be accounted twice and xsk_umem_complete_tx will move
prod_tail far beyond the prod_head breaking the completion queue ring.

Fix that by limiting the number of descriptors to clean by the number
of used descriptors in the Tx ring.

'ixgbe_clean_xdp_tx_irq()' function refactored to look more like
'ixgbe_xsk_clean_tx_ring()' since we're allowed to directly use
'next_to_clean' and 'next_to_use' indexes.

CC: stable@vger.kernel.org
Fixes: 8221c5eba8c1 ("ixgbe: add AF_XDP zero-copy Tx support")
Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Tested-by: William Tu <u9012063@gmail.com>
Tested-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 29 ++++++++++-----------------
1 file changed, 11 insertions(+), 18 deletions(-)

--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
@@ -679,19 +679,17 @@ static void ixgbe_clean_xdp_tx_buffer(st
bool ixgbe_clean_xdp_tx_irq(struct ixgbe_q_vector *q_vector,
struct ixgbe_ring *tx_ring, int napi_budget)
{
+ u16 ntc = tx_ring->next_to_clean, ntu = tx_ring->next_to_use;
unsigned int total_packets = 0, total_bytes = 0;
- u32 i = tx_ring->next_to_clean, xsk_frames = 0;
- unsigned int budget = q_vector->tx.work_limit;
struct xdp_umem *umem = tx_ring->xsk_umem;
union ixgbe_adv_tx_desc *tx_desc;
struct ixgbe_tx_buffer *tx_bi;
- bool xmit_done;
+ u32 xsk_frames = 0;

- tx_bi = &tx_ring->tx_buffer_info[i];
- tx_desc = IXGBE_TX_DESC(tx_ring, i);
- i -= tx_ring->count;
+ tx_bi = &tx_ring->tx_buffer_info[ntc];
+ tx_desc = IXGBE_TX_DESC(tx_ring, ntc);

- do {
+ while (ntc != ntu) {
if (!(tx_desc->wb.status & cpu_to_le32(IXGBE_TXD_STAT_DD)))
break;

@@ -708,22 +706,18 @@ bool ixgbe_clean_xdp_tx_irq(struct ixgbe

tx_bi++;
tx_desc++;
- i++;
- if (unlikely(!i)) {
- i -= tx_ring->count;
+ ntc++;
+ if (unlikely(ntc == tx_ring->count)) {
+ ntc = 0;
tx_bi = tx_ring->tx_buffer_info;
tx_desc = IXGBE_TX_DESC(tx_ring, 0);
}

/* issue prefetch for next Tx descriptor */
prefetch(tx_desc);
+ }

- /* update budget accounting */
- budget--;
- } while (likely(budget));
-
- i += tx_ring->count;
- tx_ring->next_to_clean = i;
+ tx_ring->next_to_clean = ntc;

u64_stats_update_begin(&tx_ring->syncp);
tx_ring->stats.bytes += total_bytes;
@@ -735,8 +729,7 @@ bool ixgbe_clean_xdp_tx_irq(struct ixgbe
if (xsk_frames)
xsk_umem_complete_tx(umem, xsk_frames);

- xmit_done = ixgbe_xmit_zc(tx_ring, q_vector->tx.work_limit);
- return budget > 0 && xmit_done;
+ return ixgbe_xmit_zc(tx_ring, q_vector->tx.work_limit);
}

int ixgbe_xsk_async_xmit(struct net_device *dev, u32 qid)