i40e: use xdp.frame_sz as XDP RxQ info frag_size

The only user of frag_size field in XDP RxQ info is
bpf_xdp_frags_increase_tail(). It clearly expects whole buffer size instead
of DMA write size. Different assumptions in i40e driver configuration lead
to negative tailroom.

Set frag_size to the same value as frame_sz in shared pages mode, use new
helper to set frag_size when AF_XDP ZC is active.

Fixes: a045d2f ("i40e: set xdp_rxq_info::frag_size")
Reviewed-by: Aleksandr Loktionov <[email protected]>
Signed-off-by: Larysa Zaremba <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: walking-machine

drivers/net/ethernet/intel/i40e/i40e_main.c

@@ -3569,6 +3569,7 @@ static int i40e_configure_rx_ring(struct i40e_ring *ring)
 	u16 pf_q = vsi->base_queue + ring->queue_index;
 	struct i40e_hw *hw = &vsi->back->hw;
 	struct i40e_hmc_obj_rxq rx_ctx;
+	u32 xdp_frame_sz;
 	int err = 0;
 	bool ok;
 
@@ -3578,18 +3579,20 @@ static int i40e_configure_rx_ring(struct i40e_ring *ring)
 	memset(&rx_ctx, 0, sizeof(rx_ctx));
 
 	ring->rx_buf_len = vsi->rx_buf_len;
+	xdp_frame_sz = i40e_rx_pg_size(ring) / 2;
 
 	/* XDP RX-queue info only needed for RX rings exposed to XDP */
 	if (ring->vsi->type != I40E_VSI_MAIN)
 		goto skip;
 
 	ring->xsk_pool = i40e_xsk_pool(ring);
 	if (ring->xsk_pool) {
+		xdp_frame_sz = xsk_pool_get_rx_frag_step(ring->xsk_pool);
 		ring->rx_buf_len = xsk_pool_get_rx_frame_size(ring->xsk_pool);
 		err = __xdp_rxq_info_reg(&ring->xdp_rxq, ring->netdev,
 					 ring->queue_index,
 					 ring->q_vector->napi.napi_id,
-					 ring->rx_buf_len);
+					 xdp_frame_sz);
 		if (err)
 			return err;
 		err = xdp_rxq_info_reg_mem_model(&ring->xdp_rxq,
@@ -3605,7 +3608,7 @@ static int i40e_configure_rx_ring(struct i40e_ring *ring)
 		err = __xdp_rxq_info_reg(&ring->xdp_rxq, ring->netdev,
 					 ring->queue_index,
 					 ring->q_vector->napi.napi_id,
-					 ring->rx_buf_len);
+					 xdp_frame_sz);
 		if (err)
 			return err;
 		err = xdp_rxq_info_reg_mem_model(&ring->xdp_rxq,
@@ -3616,7 +3619,7 @@ static int i40e_configure_rx_ring(struct i40e_ring *ring)
 	}
 
 skip:
-	xdp_init_buff(&ring->xdp, i40e_rx_pg_size(ring) / 2, &ring->xdp_rxq);
+	xdp_init_buff(&ring->xdp, xdp_frame_sz, &ring->xdp_rxq);
 
 	rx_ctx.dbuff = DIV_ROUND_UP(ring->rx_buf_len,
 				    BIT_ULL(I40E_RXQ_CTX_DBUFF_SHIFT));