Messages in this thread | | | Date | Sun, 26 Mar 2023 17:10:06 +0200 | Subject | Re: [Intel-wired-lan] [PATCH net v3] ixgbe: Panic during XDP_TX with > 64 CPUs | From | Paul Menzel <> |
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[Cc: Remove undeliverable <xingwanli@kuaishou.com>]
Am 26.03.23 um 17:03 schrieb Paul Menzel: > Dear John, > > > Thank you for your patch. > > I’d recommend, to use a statement in the git commit message/summary by > adding a verb (in imperative mood). Maybe: > > Fix panic during XDP_TX with > 64 CPUs > > Am 08.03.23 um 23:07 schrieb John Hickey: >> In commit 'ixgbe: let the xdpdrv work with more than 64 cpus' >> (4fe815850bdc), support was added to allow XDP programs to run on systems > > I think it’s more common to write it like: > > In commit 4fe815850bdc (ixgbe: let the xdpdrv work with more than 64 > cpus) … > > Even shorter > > Commit 4fe815850bdc (ixgbe: let the xdpdrv work with more than 64 cpus) > adds support to allow XDP programs … > >> with more than 64 CPUs by locking the XDP TX rings and indexing them >> using cpu % 64 (IXGBE_MAX_XDP_QS). >> >> Upon trying this out patch via the Intel 5.18.6 out of tree driver > > Upon trying this patch out via … > >> on a system with more than 64 cores, the kernel paniced with an >> array-index-out-of-bounds at the return in ixgbe_determine_xdp_ring in >> ixgbe.h, which means ixgbe_determine_xdp_q_idx was just returning the >> cpu instead of cpu % IXGBE_MAX_XDP_QS. An example splat: > > Please add, that you have UBSAN enabled, or does it happen without? > >> >> >> ========================================================================== >> UBSAN: array-index-out-of-bounds in >> /var/lib/dkms/ixgbe/5.18.6+focal-1/build/src/ixgbe.h:1147:26 >> index 65 is out of range for type 'ixgbe_ring *[64]' >> >> ========================================================================== >> BUG: kernel NULL pointer dereference, address: 0000000000000058 >> #PF: supervisor read access in kernel mode >> #PF: error_code(0x0000) - not-present page >> PGD 0 P4D 0 >> Oops: 0000 [#1] SMP NOPTI >> CPU: 65 PID: 408 Comm: ksoftirqd/65 >> Tainted: G IOE 5.15.0-48-generic #54~20.04.1-Ubuntu >> Hardware name: Dell Inc. PowerEdge R640/0W23H8, BIOS 2.5.4 01/13/2020 >> RIP: 0010:ixgbe_xmit_xdp_ring+0x1b/0x1c0 [ixgbe] >> Code: 3b 52 d4 cf e9 42 f2 ff ff 66 0f 1f 44 00 00 0f 1f 44 00 00 55 b9 >> 00 00 00 00 48 89 e5 41 57 41 56 41 55 41 54 53 48 83 ec 08 <44> 0f b7 >> 47 58 0f b7 47 5a 0f b7 57 54 44 0f b7 76 08 66 41 39 c0 > > If you do not it yet, `scripts/decode_stacktrace.sh` helps decoding > these traces. > >> RSP: 0018:ffffbc3fcd88fcb0 EFLAGS: 00010282 >> RAX: ffff92a253260980 RBX: ffffbc3fe68b00a0 RCX: 0000000000000000 >> RDX: ffff928b5f659000 RSI: ffff928b5f659000 RDI: 0000000000000000 >> RBP: ffffbc3fcd88fce0 R08: ffff92b9dfc20580 R09: 0000000000000001 >> R10: 3d3d3d3d3d3d3d3d R11: 3d3d3d3d3d3d3d3d R12: 0000000000000000 >> R13: ffff928b2f0fa8c0 R14: ffff928b9be20050 R15: 000000000000003c >> FS: 0000000000000000(0000) GS:ffff92b9dfc00000(0000) >> knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 0000000000000058 CR3: 000000011dd6a002 CR4: 00000000007706e0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> PKRU: 55555554 >> Call Trace: >> <TASK> >> ixgbe_poll+0x103e/0x1280 [ixgbe] >> ? sched_clock_cpu+0x12/0xe0 >> __napi_poll+0x30/0x160 >> net_rx_action+0x11c/0x270 >> __do_softirq+0xda/0x2ee >> run_ksoftirqd+0x2f/0x50 >> smpboot_thread_fn+0xb7/0x150 >> ? sort_range+0x30/0x30 >> kthread+0x127/0x150 >> ? set_kthread_struct+0x50/0x50 >> ret_from_fork+0x1f/0x30 >> </TASK> >> >> I think this is how it happens: >> >> Upon loading the first XDP program on a system with more than 64 CPUs, >> ixgbe_xdp_locking_key is incremented in ixgbe_xdp_setup. However, >> immediately after this, the rings are reconfigured by ixgbe_setup_tc. >> ixgbe_setup_tc calls ixgbe_clear_interrupt_scheme which calls >> ixgbe_free_q_vectors which calls ixgbe_free_q_vector in a loop. >> ixgbe_free_q_vector decrements ixgbe_xdp_locking_key once per call if >> it is non-zero. Commenting out the decrement in ixgbe_free_q_vector >> stopped my system from panicing. >> >> I suspect to make the original patch work, I would need to load an XDP >> program and then replace it in order to get ixgbe_xdp_locking_key back >> above 0 since ixgbe_setup_tc is only called when transitioning between >> XDP and non-XDP ring configurations, while ixgbe_xdp_locking_key is >> incremented every time ixgbe_xdp_setup is called. >> >> Also, ixgbe_setup_tc can be called via ethtool --set-channels, so this >> becomes another path to decrement ixgbe_xdp_locking_key to 0 on systems >> with greater than 64 CPUs. > > … with more than 64 CPUs. > >> For this patch, I have changed static_branch_inc to static_branch_enable >> in ixgbe_setup_xdp. We weren't counting references. The >> ixgbe_xdp_locking_key only protects code in the XDP_TX path, which is >> not run when an XDP program is loaded. The other condition for setting >> it on is the number of CPUs, which I assume is static. >> >> Fixes: 4fe815850bdc ("ixgbe: let the xdpdrv work with more than 64 cpus") >> Signed-off-by: John Hickey <jjh@daedalian.us> >> --- >> v1 -> v2: >> Added Fixes and net tag. No code changes. >> v2 -> v3: >> Added splat. Slight clarification as to why ixgbe_xdp_locking_key >> is not turned off. Based on feedback from Maciej Fijalkowski. >> --- >> drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c | 3 --- >> drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 2 +- >> 2 files changed, 1 insertion(+), 4 deletions(-) >> >> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c >> b/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c >> index f8156fe4b1dc..0ee943db3dc9 100644 >> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c >> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c >> @@ -1035,9 +1035,6 @@ static void ixgbe_free_q_vector(struct >> ixgbe_adapter *adapter, int v_idx) >> adapter->q_vector[v_idx] = NULL; >> __netif_napi_del(&q_vector->napi); >> - if (static_key_enabled(&ixgbe_xdp_locking_key)) >> - static_branch_dec(&ixgbe_xdp_locking_key); >> - >> /* >> * after a call to __netif_napi_del() napi may still be used and >> * ixgbe_get_stats64() might access the rings on this vector, >> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c >> b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c >> index ab8370c413f3..cd2fb72c67be 100644 >> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c >> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c >> @@ -10283,7 +10283,7 @@ static int ixgbe_xdp_setup(struct net_device >> *dev, struct bpf_prog *prog) >> if (nr_cpu_ids > IXGBE_MAX_XDP_QS * 2) >> return -ENOMEM; >> else if (nr_cpu_ids > IXGBE_MAX_XDP_QS) >> - static_branch_inc(&ixgbe_xdp_locking_key); >> + static_branch_enable(&ixgbe_xdp_locking_key); >> old_prog = xchg(&adapter->xdp_prog, prog); >> need_reset = (!!prog != !!old_prog); > > > Kind regards, > > Paul
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