Commit 49589b23 authored by Toke Høiland-Jørgensen's avatar Toke Høiland-Jørgensen Committed by Daniel Borkmann
Browse files

intel: Remove rcu_read_lock() around XDP program invocation 



The Intel drivers all have rcu_read_lock()/rcu_read_unlock() pairs around
XDP program invocations. However, the actual lifetime of the objects
referred by the XDP program invocation is longer, all the way through to
the call to xdp_do_flush(), making the scope of the rcu_read_lock() too
small. This turns out to be harmless because it all happens in a single
NAPI poll cycle (and thus under local_bh_disable()), but it makes the
rcu_read_lock() misleading.

Rather than extend the scope of the rcu_read_lock(), just get rid of it
entirely. With the addition of RCU annotations to the XDP_REDIRECT map
types that take bh execution into account, lockdep even understands this to
be safe, so there's really no reason to keep it around.

Signed-off-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Tested-by: Jesper Dangaard Brouer <brouer@redhat.com> # i40e
Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>
Cc: Tony Nguyen <anthony.l.nguyen@intel.com>
Cc: intel-wired-lan@lists.osuosl.org
Link: https://lore.kernel.org/bpf/20210624160609.292325-12-toke@redhat.com
parent 547aabca

drivers/net/ethernet/intel/i40e/i40e_txrx.c

+0 −2
Original line number Diff line number Diff line
@@ -2298,7 +2298,6 @@ static int i40e_run_xdp(struct i40e_ring *rx_ring, struct xdp_buff *xdp) 
	struct bpf_prog *xdp_prog;

	u32 act;



	rcu_read_lock();

	xdp_prog = READ_ONCE(rx_ring->xdp_prog);



	if (!xdp_prog)
@@ -2334,7 +2333,6 @@ static int i40e_run_xdp(struct i40e_ring *rx_ring, struct xdp_buff *xdp) 
		break;

	}

xdp_out:

	rcu_read_unlock();

	return result;

}

drivers/net/ethernet/intel/i40e/i40e_xsk.c

+0 −3
Original line number Diff line number Diff line
@@ -153,7 +153,6 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp) 
	struct bpf_prog *xdp_prog;

	u32 act;



	rcu_read_lock();

	/* NB! xdp_prog will always be !NULL, due to the fact that

	 * this path is enabled by setting an XDP program.

	 */
@@ -164,7 +163,6 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp) 
		err = xdp_do_redirect(rx_ring->netdev, xdp, xdp_prog);

		if (err)

			goto out_failure;

		rcu_read_unlock();

		return I40E_XDP_REDIR;

	}
@@ -188,7 +186,6 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp) 
		result = I40E_XDP_CONSUMED;

		break;

	}

	rcu_read_unlock();

	return result;

}

drivers/net/ethernet/intel/ice/ice_txrx.c

+1 −5
Original line number Diff line number Diff line
@@ -1135,15 +1135,11 @@ int ice_clean_rx_irq(struct ice_ring *rx_ring, int budget) 
		xdp.frame_sz = ice_rx_frame_truesize(rx_ring, size);

#endif



		rcu_read_lock();

		xdp_prog = READ_ONCE(rx_ring->xdp_prog);

		if (!xdp_prog) {

			rcu_read_unlock();

		if (!xdp_prog)

			goto construct_skb;

		}



		xdp_res = ice_run_xdp(rx_ring, &xdp, xdp_prog);

		rcu_read_unlock();

		if (!xdp_res)

			goto construct_skb;

		if (xdp_res & (ICE_XDP_TX | ICE_XDP_REDIR)) {

drivers/net/ethernet/intel/ice/ice_xsk.c

+0 −3
Original line number Diff line number Diff line
@@ -466,7 +466,6 @@ ice_run_xdp_zc(struct ice_ring *rx_ring, struct xdp_buff *xdp) 
	struct ice_ring *xdp_ring;

	u32 act;



	rcu_read_lock();

	/* ZC patch is enabled only when XDP program is set,

	 * so here it can not be NULL

	 */
@@ -478,7 +477,6 @@ ice_run_xdp_zc(struct ice_ring *rx_ring, struct xdp_buff *xdp) 
		err = xdp_do_redirect(rx_ring->netdev, xdp, xdp_prog);

		if (err)

			goto out_failure;

		rcu_read_unlock();

		return ICE_XDP_REDIR;

	}
@@ -503,7 +501,6 @@ ice_run_xdp_zc(struct ice_ring *rx_ring, struct xdp_buff *xdp) 
		break;

	}



	rcu_read_unlock();

	return result;

}

drivers/net/ethernet/intel/igb/igb_main.c

+0 −2
Original line number Diff line number Diff line
@@ -8381,7 +8381,6 @@ static struct sk_buff *igb_run_xdp(struct igb_adapter *adapter, 
	struct bpf_prog *xdp_prog;

	u32 act;



	rcu_read_lock();

	xdp_prog = READ_ONCE(rx_ring->xdp_prog);



	if (!xdp_prog)
@@ -8416,7 +8415,6 @@ static struct sk_buff *igb_run_xdp(struct igb_adapter *adapter, 
		break;

	}

xdp_out:

	rcu_read_unlock();

	return ERR_PTR(-result);

}