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i40e, xsk: clear the status bits for the next_to_use descriptor 

On the Rx side, the next_to_use index points to the next item in the
HW ring to be refilled/allocated, and next_to_clean points to the next
item to potentially be processed.

When the HW Rx ring is fully refilled, i.e. no packets has been
processed, the next_to_use will be next_to_clean - 1. When the ring is
fully processed next_to_clean will be equal to next_to_use. The latter
case is where a bug is triggered.

If the next_to_use bits are not cleared, and the "fully processed"
state is entered, a stale descriptor can be processed.

The skb-path correctly clear the status bit for the next_to_use
descriptor, but the AF_XDP zero-copy path did not do that.

This change adds the status bits clearing of the next_to_use
descriptor.

Fixes: 3b4f0b66c2 ("i40e, xsk: Migrate to new MEM_TYPE_XSK_BUFF_POOL")
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Björn Töpel 2020-12-11 15:57:12 +01:00 committed by Jakub Kicinski
parent 8d14768a79
commit 64050b5b87
1 changed files with 4 additions and 1 deletions
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5
drivers/net/ethernet/intel/i40e/i40e_xsk.c
View File

@ -220,8 +220,11 @@ bool i40e_alloc_rx_buffers_zc(struct i40e_ring *rx_ring, u16 count)
} while (count);
no_buffers:
if (rx_ring->next_to_use != ntu)
if (rx_ring->next_to_use != ntu) {
/* clear the status bits for the next_to_use descriptor */
rx_desc->wb.qword1.status_error_len = 0;
i40e_release_rx_desc(rx_ring, ntu);
}
return ok;
}