netdev - [PATCH intel-net] ice: xsk: disable txq irq before flushing hw

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Message-Id: <20230216122839.6878-1-maciej.fijalkowski@intel.com>
Date:   Thu, 16 Feb 2023 13:28:39 +0100
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     intel-wired-lan@...ts.osuosl.org
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        anthony.l.nguyen@...el.com, magnus.karlsson@...el.com,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Subject: [PATCH intel-net] ice: xsk: disable txq irq before flushing hw

ice_qp_dis() intends to stop a given queue pair that is a target of xsk
pool attach/detach. One of the steps is to disable interrupts on these
queues. It currently is broken in a way that txq irq is turned off
*after* HW flush which in turn takes no effect.

ice_qp_dis():
-> ice_qvec_dis_irq()
--> disable rxq irq
--> flush hw
-> ice_vsi_stop_tx_ring()
-->disable txq irq

Below splat can be triggered by following steps:
- start xdpsock WITHOUT loading xdp prog
- run xdp_rxq_info with XDP_TX action on this interface
- start traffic
- terminate xdpsock

[  256.312485] BUG: kernel NULL pointer dereference, address: 0000000000000018
[  256.319560] #PF: supervisor read access in kernel mode
[  256.324775] #PF: error_code(0x0000) - not-present page
[  256.329994] PGD 0 P4D 0
[  256.332574] Oops: 0000 [#1] PREEMPT SMP NOPTI
[  256.337006] CPU: 3 PID: 32 Comm: ksoftirqd/3 Tainted: G           OE      6.2.0-rc5+ #51
[  256.345218] Hardware name: Intel Corporation S2600WFT/S2600WFT, BIOS SE5C620.86B.02.01.0008.031920191559 03/19/2019
[  256.355807] RIP: 0010:ice_clean_rx_irq_zc+0x9c/0x7d0 [ice]
[  256.361423] Code: b7 8f 8a 00 00 00 66 39 ca 0f 84 f1 04 00 00 49 8b 47 40 4c 8b 24 d0 41 0f b7 45 04 66 25 ff 3f 66 89 04 24 0f 84 85 02 00 00 <49> 8b 44 24 18 0f b7 14 24 48 05 00 01 00 00 49 89 04 24 49 89 44
[  256.380463] RSP: 0018:ffffc900088bfd20 EFLAGS: 00010206
[  256.385765] RAX: 000000000000003c RBX: 0000000000000035 RCX: 000000000000067f
[  256.393012] RDX: 0000000000000775 RSI: 0000000000000000 RDI: ffff8881deb3ac80
[  256.400256] RBP: 000000000000003c R08: ffff889847982710 R09: 0000000000010000
[  256.407500] R10: ffffffff82c060c0 R11: 0000000000000004 R12: 0000000000000000
[  256.414746] R13: ffff88811165eea0 R14: ffffc9000d255000 R15: ffff888119b37600
[  256.421990] FS:  0000000000000000(0000) GS:ffff8897e0cc0000(0000) knlGS:0000000000000000
[  256.430207] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  256.436036] CR2: 0000000000000018 CR3: 0000000005c0a006 CR4: 00000000007706e0
[  256.443283] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  256.450527] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  256.457770] PKRU: 55555554
[  256.460529] Call Trace:
[  256.463015]  <TASK>
[  256.465157]  ? ice_xmit_zc+0x6e/0x150 [ice]
[  256.469437]  ice_napi_poll+0x46d/0x680 [ice]
[  256.473815]  ? _raw_spin_unlock_irqrestore+0x1b/0x40
[  256.478863]  __napi_poll+0x29/0x160
[  256.482409]  net_rx_action+0x136/0x260
[  256.486222]  __do_softirq+0xe8/0x2e5
[  256.489853]  ? smpboot_thread_fn+0x2c/0x270
[  256.494108]  run_ksoftirqd+0x2a/0x50
[  256.497747]  smpboot_thread_fn+0x1c1/0x270
[  256.501907]  ? __pfx_smpboot_thread_fn+0x10/0x10
[  256.506594]  kthread+0xea/0x120
[  256.509785]  ? __pfx_kthread+0x10/0x10
[  256.513597]  ret_from_fork+0x29/0x50
[  256.517238]  </TASK>

In fact, irqs were not disabled and napi managed to be scheduled and run
while xsk_pool pointer was still valid, but SW ring of xdp_buff pointers
was already freed.

To fix this, call ice_qvec_dis_irq() after ice_vsi_stop_tx_ring(). Also
while at it, remove redundant ice_clean_rx_ring() call - this is handled
in ice_qp_clean_rings().

Fixes: 2d4238f55697 ("ice: Add support for AF_XDP")
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
---
 drivers/net/ethernet/intel/ice/ice_xsk.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
index 917c75e530ca..6b8aeaa32d0b 100644
--- a/drivers/net/ethernet/intel/ice/ice_xsk.c
+++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
@@ -184,8 +184,6 @@ static int ice_qp_dis(struct ice_vsi *vsi, u16 q_idx)
 	}
 	netif_tx_stop_queue(netdev_get_tx_queue(vsi->netdev, q_idx));
 
-	ice_qvec_dis_irq(vsi, rx_ring, q_vector);
-
 	ice_fill_txq_meta(vsi, tx_ring, &txq_meta);
 	err = ice_vsi_stop_tx_ring(vsi, ICE_NO_RESET, 0, tx_ring, &txq_meta);
 	if (err)
@@ -200,10 +198,11 @@ static int ice_qp_dis(struct ice_vsi *vsi, u16 q_idx)
 		if (err)
 			return err;
 	}
+	ice_qvec_dis_irq(vsi, rx_ring, q_vector);
+
 	err = ice_vsi_ctrl_one_rx_ring(vsi, false, q_idx, true);
 	if (err)
 		return err;
-	ice_clean_rx_ring(rx_ring);
 
 	ice_qvec_toggle_napi(vsi, q_vector, false);
 	ice_qp_clean_rings(vsi, q_idx);
-- 
2.34.1