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ice: Fix XDP Tx ring overrun

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Sometimes, under heavy XDP Tx traffic, e.g. when using XDP traffic
generator (%BPF_F_TEST_XDP_LIVE_FRAMES), the machine can catch OOM due
to the driver not freeing all of the pages passed to it by
.ndo_xdp_xmit().
Turned out that during the development of the tagged commit, the check,
which ensures that we have a free descriptor to queue a frame, moved
into the branch happening only when a buffer has frags. Otherwise, we
only run a cleaning cycle, but don't check anything.
ATST, there can be situations when the driver gets new frames to send,
but there are no buffers that can be cleaned/completed and the ring has
no free slots. It's very rare, but still possible (> 6.5 Mpps per ring).
The driver then fills the next buffer/descriptor, effectively
overwriting the data, which still needs to be freed.

Restore the check after the cleaning routine to make sure there is a
slot to queue a new frame. When there are frags, there still will be a
separate check that we can place all of them, but if the ring is full,
there's no point in wasting any more time.

(minor: make `!ready_frames` unlikely since it happens ~1-2 times per
 billion of frames)

Fixes: 3246a10752 ("ice: Add support for XDP multi-buffer on Tx side")
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/bpf/20230210170618.1973430-3-alexandr.lobakin@intel.com
This commit is contained in:
Alexander Lobakin 2023-02-10 18:06:14 +01:00 committed by Daniel Borkmann
parent bc4db83470
commit 0bd939b60c
1 changed files with 12 additions and 7 deletions
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19
drivers/net/ethernet/intel/ice/ice_txrx_lib.c
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@ -260,7 +260,7 @@ static u32 ice_clean_xdp_irq(struct ice_tx_ring *xdp_ring)
ready_frames = idx + cnt - ntc + 1;
}
if (!ready_frames)
if (unlikely(!ready_frames))
return 0;
ret = ready_frames;
@ -322,17 +322,17 @@ int __ice_xmit_xdp_ring(struct xdp_buff *xdp, struct ice_tx_ring *xdp_ring)
u32 frag = 0;
free_space = ICE_DESC_UNUSED(xdp_ring);
if (ICE_DESC_UNUSED(xdp_ring) < ICE_RING_QUARTER(xdp_ring))
if (free_space < ICE_RING_QUARTER(xdp_ring))
free_space += ice_clean_xdp_irq(xdp_ring);
if (unlikely(!free_space))
goto busy;
if (unlikely(xdp_buff_has_frags(xdp))) {
sinfo = xdp_get_shared_info_from_buff(xdp);
nr_frags = sinfo->nr_frags;
if (free_space < nr_frags + 1) {
xdp_ring->ring_stats->tx_stats.tx_busy++;
return ICE_XDP_CONSUMED;
}
if (free_space < nr_frags + 1)
goto busy;
}
tx_desc = ICE_TX_DESC(xdp_ring, ntu);
@ -396,6 +396,11 @@ int __ice_xmit_xdp_ring(struct xdp_buff *xdp, struct ice_tx_ring *xdp_ring)
ntu--;
}
return ICE_XDP_CONSUMED;
busy:
xdp_ring->ring_stats->tx_stats.tx_busy++;
return ICE_XDP_CONSUMED;
}
/**