RE: [Intel-wired-lan] [PATCH intel-net] ice: xsk: disable txq irq before flushing hw

["Rout, ChandanX" <chandanx.rout@intel.com>]

>-----Original Message-----
>From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf Of
>Fijalkowski, Maciej
>Sent: 16 February 2023 17:59
>To: intel-wired-lan@lists.osuosl.org
>Cc: netdev@vger.kernel.org; bpf@vger.kernel.org; Nguyen, Anthony L
><anthony.l.nguyen@intel.com>; Karlsson, Magnus
><magnus.karlsson@intel.com>
>Subject: [Intel-wired-lan] [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@intel.com>
>---
> drivers/net/ethernet/intel/ice/ice_xsk.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>

Tested-by: Chandan Kumar Rout <chandanx.rout@intel.com> (A Contingent Worker at Intel)