From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0C3DDC43603 for ; Thu, 19 Dec 2019 14:27:21 +0000 (UTC) Received: from lists.ozlabs.org (unknown [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8387C24672 for ; Thu, 19 Dec 2019 14:27:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8387C24672 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kaod.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 47dvN62t7gzDqtV for ; Fri, 20 Dec 2019 01:27:18 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kaod.org (client-ip=46.105.53.132; helo=6.mo178.mail-out.ovh.net; envelope-from=clg@kaod.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kaod.org X-Greylist: delayed 4200 seconds by postgrey-1.36 at bilbo; Fri, 20 Dec 2019 01:24:28 AEDT Received: from 6.mo178.mail-out.ovh.net (6.mo178.mail-out.ovh.net [46.105.53.132]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 47dvJr6VCczDqsG for ; Fri, 20 Dec 2019 01:24:23 +1100 (AEDT) Received: from player730.ha.ovh.net (unknown [10.108.42.102]) by mo178.mail-out.ovh.net (Postfix) with ESMTP id 4DCA6898C1 for ; Thu, 19 Dec 2019 14:08:45 +0100 (CET) Received: from kaod.org (lfbn-tou-1-1227-223.w90-76.abo.wanadoo.fr [90.76.50.223]) (Authenticated sender: clg@kaod.org) by player730.ha.ovh.net (Postfix) with ESMTPSA id 292B1D59D2F3; Thu, 19 Dec 2019 13:08:30 +0000 (UTC) Subject: Re: [Qemu-ppc] pseries on qemu-system-ppc64le crashes in doorbell_core_ipi() To: Michael Ellerman , "Jason A. Donenfeld" , Sebastian Andrzej Siewior , qemu-ppc@nongnu.org, linuxppc-dev@lists.ozlabs.org References: <20190327123615.rwhk6h3ayfurvapf@linutronix.de> <7d97f3c6-4614-ead7-179a-e7e223ea3997@kaod.org> <2bbc1490-400d-585e-d74b-924c570b4236@kaod.org> <1553836851.2264.2.camel@gmail.com> <1553850306.nyv11r9iej.astroid@bobo.none> <20190329113109.3a9bd24e@gandalf.local.home> <1553912871.ce5mzizoek.astroid@bobo.none> <20190401083827.GE11158@hirez.programming.kicks-ass.net> <20190406000611.GA27782@lenoir> <1554801792.ruzup3dxhe.astroid@bobo.none> <7a5b63a0-2bf5-60bb-8678-b7b36671a29c@zx2c4.com> <871rt0mql5.fsf@mpe.ellerman.id.au> From: =?UTF-8?Q?C=c3=a9dric_Le_Goater?= Message-ID: <42d35390-0661-8d1e-d335-03186ee7ec93@kaod.org> Date: Thu, 19 Dec 2019 14:08:29 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <871rt0mql5.fsf@mpe.ellerman.id.au> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Ovh-Tracer-Id: 8528973272626793446 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedufedrvdduuddggeejucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuqfggjfdpvefjgfevmfevgfenuceurghilhhouhhtmecuhedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujfgurhepuffvfhfhkffffgggjggtgfesthejredttdefjeenucfhrhhomhepveorughrihgtpgfnvggpifhorghtvghruceotghlgheskhgrohgurdhorhhgqeenucffohhmrghinhepfihirhgvghhurghrugdrtghomhdpghhithhhuhgsrdgtohhmnecukfhppedtrddtrddtrddtpdeltddrjeeirdehtddrvddvfeenucfrrghrrghmpehmohguvgepshhmthhpqdhouhhtpdhhvghlohepphhlrgihvghrjeeftddrhhgrrdhovhhhrdhnvghtpdhinhgvtheptddrtddrtddrtddpmhgrihhlfhhrohhmpegtlhhgsehkrghougdrohhrghdprhgtphhtthhopehlihhnuhigphhptgdquggvvheslhhishhtshdrohiilhgrsghsrdhorhhgnecuvehluhhsthgvrhfuihiivgeptd X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Zijlstra , Frederic Weisbecker , Frederic Weisbecker , Nicholas Piggin , Paul Mackerras , Steven Rostedt , Suraj Jitindar Singh , tglx@linutronix.de, David? Gibson Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 19/12/2019 13:45, Michael Ellerman wrote: > "Jason A. Donenfeld" writes: >> Hi folks, >> >> I'm actually still experiencing this sporadically in the WireGuard test >> suite, which you can see being run on https://build.wireguard.com/ . > > Fancy dashboard you got there :) > >> About 50% of the time the powerpc64 build will fail at a place like this: >> >> [ 65.147823] Oops: Exception in kernel mode, sig: 4 [#1] >> [ 65.149198] LE PAGE_SIZE=4K MMU=Hash PREEMPT SMP NR_CPUS=4 NUMA pSeries >> [ 65.149595] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.5.0-rc1+ #1 >> [ 65.149745] NIP: c000000000033330 LR: c00000000007eda0 CTR: c00000000007ed80 >> [ 65.149934] REGS: c000000000a47970 TRAP: 0700 Not tainted (5.5.0-rc1+) >> [ 65.150032] MSR: 800000000288b033 > CR: 48008288 XER: 00000000 >> [ 65.150352] CFAR: c0000000000332bc IRQMASK: 1 >> [ 65.150352] GPR00: c000000000036508 c000000000a47c00 c000000000a4c100 0000000000000001 >> [ 65.150352] GPR04: c000000000a50998 0000000000000000 c000000000a50908 000000000f509000 >> [ 65.150352] GPR08: 0000000028000000 0000000000000000 0000000000000000 c00000000ff24f00 >> [ 65.150352] GPR12: c00000000007ed80 c000000000ad9000 0000000000000000 0000000000000000 >> [ 65.150352] GPR16: 00000000008c9190 00000000008c94a8 00000000008c92f8 00000000008c98b0 >> [ 65.150352] GPR20: 00000000008f2f88 fffffffffffffffd 0000000000000014 0000000000e6c100 >> [ 65.150352] GPR24: 0000000000e6c100 0000000000000001 0000000000000000 c000000000a50998 >> [ 65.150352] GPR28: c000000000a9e280 c000000000a50aa4 0000000000000002 0000000000000000 >> [ 65.151591] NIP [c000000000033330] doorbell_try_core_ipi+0xd0/0xf0 >> [ 65.151750] LR [c00000000007eda0] smp_pseries_cause_ipi+0x20/0x70 >> [ 65.151913] Call Trace: >> [ 65.152109] [c000000000a47c00] [c0000000000c7c9c] _nohz_idle_balance+0xbc/0x300 (unreliable) >> [ 65.152370] [c000000000a47c30] [c000000000036508] smp_send_reschedule+0x98/0xb0 >> [ 65.152711] [c000000000a47c50] [c0000000000c1634] kick_ilb+0x114/0x140 >> [ 65.152962] [c000000000a47ca0] [c0000000000c86d8] newidle_balance+0x4e8/0x500 >> [ 65.153213] [c000000000a47d20] [c0000000000c8788] pick_next_task_fair+0x48/0x3a0 >> [ 65.153424] [c000000000a47d80] [c000000000466620] __schedule+0xf0/0x430 >> [ 65.153612] [c000000000a47de0] [c000000000466b04] schedule_idle+0x34/0x70 >> [ 65.153786] [c000000000a47e10] [c0000000000c0bc8] do_idle+0x1a8/0x220 >> [ 65.154121] [c000000000a47e70] [c0000000000c0e94] cpu_startup_entry+0x34/0x40 >> [ 65.154313] [c000000000a47ea0] [c00000000000ef1c] rest_init+0x10c/0x124 >> [ 65.154414] [c000000000a47ee0] [c000000000500004] start_kernel+0x568/0x594 >> [ 65.154585] [c000000000a47f90] [c00000000000a7cc] start_here_common+0x1c/0x330 >> [ 65.154854] Instruction dump: >> [ 65.155191] 38210030 e8010010 7c0803a6 4e800020 3d220004 39295228 81290000 3929ffff >> [ 65.155498] 7d284038 7c0004ac 5508017e 65082800 <7c00411c> e94d0178 812a0000 3929ffff > ^ > Again the faulting instruction there is "msgsndp r8" > >> [ 65.156155] ---[ end trace 6180d12e268ffdaf ]--- >> [ 65.185452] >> [ 66.187490] Kernel panic - not syncing: Fatal exception >> >> This is with "qemu-system-ppc64 -smp 4 -machine pseries" on QEMU 4.0.0. >> >> I'm not totally sure what's going on here. I'm emulating a pseries, and >> using that with qemu's pseries model, and I see that selecting the >> pseries forces the selection of 'config PPC_DOORBELL' (twice in the same >> section, actually). > > Noted. > >> Then inside the kernel there appears to be some runtime CPU check for >> doorbell support. > > Not really. The kernel looks at the CPU revision (PVR) and decides that > it has doorbell support. > >> Is this a case in which QEMU is advertising doorbell support that TCG >> doesn't have? Or is something else happening here? > > It's a gap in the emulation I guess. qemu doesn't emulate msgsndp, but > it really should because that's a supported instruction since Power8. There is a patch for msgsndp in my tree you could try : https://github.com/legoater/qemu/tree/powernv-5.0 Currently being reviewed. I have to address some remarks from David before it can be merged. > I suspect msgsndp wasn't implemented for TCG because TCG doesn't support > more than one thread per core, and you can only send doorbells to other > threads in the same core, and therefore there is no reason to ever use > msgsndp. There is a need now with KVM emulation under TCG, but, yes, QEMU still lacks SMT support. > That's the message Suraj mentioned up thread, eg: > > $ qemu-system-ppc64 -nographic -vga none -M pseries -smp 2,threads=2 -cpu POWER8 -kernel build~/vmlinux > qemu-system-ppc64: TCG cannot support more than 1 thread/core on a pseries machine > > > But I guess we've hit another case of a CPU sending itself an IPI, and > the way the sibling masks are done, CPUs are siblings of themselves, so > the sibling test passes, eg: > > int doorbell_try_core_ipi(int cpu) > { > int this_cpu = get_cpu(); > int ret = 0; > > if (cpumask_test_cpu(cpu, cpu_sibling_mask(this_cpu))) { > doorbell_core_ipi(cpu); > > > > In which case this patch should fix it. > > diff --git a/arch/powerpc/kernel/dbell.c b/arch/powerpc/kernel/dbell.c > index f17ff1200eaa..e45cb9bba193 100644 > --- a/arch/powerpc/kernel/dbell.c > +++ b/arch/powerpc/kernel/dbell.c > @@ -63,7 +63,7 @@ int doorbell_try_core_ipi(int cpu) > int this_cpu = get_cpu(); > int ret = 0; > > - if (cpumask_test_cpu(cpu, cpu_sibling_mask(this_cpu))) { > + if (cpu != this_cpu && cpumask_test_cpu(cpu, cpu_sibling_mask(this_cpu))) { > doorbell_core_ipi(cpu); > ret = 1; > } > > > The other option would be we disable CPU_FTR_DBELL if we detect we're > running under TCG. But I'm not sure we have a particularly clean way to > detect that. does the pseries kernel support cpufeatures in the DT ? Cheers, C.