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However, this >> triggering on the ICOSQ is done unprotected. >> >> mlx5e_trigger_irq() is called while mlx5e_xsk_alloc_rx_mpwqe() is >> running from a different CPU due to affinity change. This can happen >> because IRQ triggering is done after napi_complete_done(). At this point >> the NAPI can be scheduled on a different CPU. Like this: >> >> CPU A (old affinity, NAPI tail) CPU B (new affinity, fresh NAPI) >> ------------------------------- -------------------------------- >> napi_complete_done() clears SCHED >> mlx5e_cq_arm(...) >> napi_schedule_prep() sets SCHED >> mlx5e_napi_poll() >> mlx5e_xsk_alloc_rx_mpwqe() >> memcpy 640 B UMR body >> advance sq->pc by 10 >> mlx5e_trigger_irq(&c->icosq) >> wqe_info[pi] = {NOP, 1} >> mlx5e_post_nop() advances sq->pc >> >> The obvious fix would be to lock the ICOSQ. But the ICOSQ is expected to >> be accessed only from the channel's NAPI and has no locking. Kick the >> async ICOSQ instead which is always locked. >> >> This issue was noticed in the wild with the following splat: >> >> netdevice: ge-0-0-1: Bad OP in ICOSQ CQE: 0xd >> WARNING: drivers/net/ethernet/mellanox/mlx5/core/en_rx.c:826 [...] >> [...] >> Call Trace: >> >> mlx5e_napi_poll+0x11d/0x7f0 [mlx5_core] >> __napi_poll+0x30/0x200 >> ? skb_defer_free_flush+0x9c/0xc0 >> net_rx_action+0x2fe/0x3f0 >> handle_softirqs+0xd8/0x340 >> __irq_exit_rcu+0xbc/0xe0 >> common_interrupt+0x85/0xa0 >> >> >> asm_common_interrupt+0x26/0x40 >> [...] >> ---[ end trace 0000000000000000 ]--- >> mlx5_core 0000:08:00.0 ge-0-0-1: Error cqe on cqn 0x548, ci 0x2022, qn 0x8f4, >> opcode 0xd, syndrome 0x2, vendor syndrome 0x68 > > Why does the changelog here differ from what is in Linus's tree? > > Please don't do that :( > Apologies. Will fix. >> [ Backport to 6.18.y and older: upstream commit calls >> mlx5e_trigger_napi_async_icosq(), which was introduced by commit >> 0da1dba72616 ("net/mlx5e: XSK, Fix unintended ICOSQ change") and is not >> present here. In these trees mlx5e_trigger_napi_icosq() is the >> equivalent helper: it takes c->async_icosq_lock and triggers >> c->async_icosq, which is unconditionally opened, activated, polled and >> armed for every channel. Race B of the upstream commit message does not >> apply, as it concerns the sync-ICOSQ variant of >> mlx5e_trigger_napi_icosq() that only exists upstream. ] > > That part is ok, but changing the overall changelog text for no obvious > reson isn't ok. > Do you prefer that I drop it in v2. Also, should I prefix the next patch with v2? (First time sending a stable patch like this) Thanks, Dragos