From nobody Tue Feb 10 02:04:52 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2C6BEE49B2 for ; Tue, 22 Aug 2023 21:30:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231331AbjHVVbA (ORCPT ); Tue, 22 Aug 2023 17:31:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42912 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231314AbjHVVa6 (ORCPT ); Tue, 22 Aug 2023 17:30:58 -0400 Received: from mail-pl1-x635.google.com (mail-pl1-x635.google.com [IPv6:2607:f8b0:4864:20::635]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3F955E49 for ; Tue, 22 Aug 2023 14:30:53 -0700 (PDT) Received: by mail-pl1-x635.google.com with SMTP id d9443c01a7336-1bf3a2f4528so36871805ad.2 for ; Tue, 22 Aug 2023 14:30:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1692739852; x=1693344652; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=rKZ6vpkmoXshy0WXF69vUhU6JiKC/AMqd7Fq/TEmz2w=; b=e0UE++PmLtN2Wv0Jj/gw8YSmQIuKof+cdGUnV8LtEBcFGaV1iIh3pI90em7t8Wg+Ia Zp++cPMF6vyua9rsgbr+BqpbFkssXLC2YN/xcuinOzPtTi2Fmr0KtHvjcTBKd3zak4aQ 7qDORQFpfMRhhs9NKqGq93HCYinF2lvC9agZw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692739852; x=1693344652; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=rKZ6vpkmoXshy0WXF69vUhU6JiKC/AMqd7Fq/TEmz2w=; b=P08LP91oHJ3SimknxBzMsh6/nhVoCCIklKol7e3TJqLashRwRXJ1hNxVA8hYXCDWiR RCLmJkgasV2UVMYYzMzkhdDxDEGO5GyIexGczRMUN2ErQ9EJG18Gl/iWN6MBYUF+0rcn JYNiTRkEheCtBhmvh+t+qoGj1eFxgc5BmLldr+hB7DGvtbiMbp0DvqlHwiZjaVyiHKFS OpQLqWLhOCbFuSq563IfYsU1udscyVaEIZejYT3YB2jYRU+/nFwdz6ORCip725e4tBhq XYi7wxtOIwfV478fqhlog1ACI94DSzYqAXpB/n8Zu24xKMJaOnxpRFjfST0HpzZewrA7 7/3g== X-Gm-Message-State: AOJu0Yyf8uEXLFU2mnRMkm8TGmgEP0iRMP6whYpL82uCHJtM5SJ3RzU8 JWJjYnR5aCjb7g+TAMZa+ZfaPQ== X-Google-Smtp-Source: AGHT+IHv614Zsz+g1uwMiDi74vgcx/0NSFoXfnRW0gsCWP7mBJdr1fbUHmRVXO/8i4UzaPLRDck+7g== X-Received: by 2002:a17:902:efc1:b0:1bc:66a3:9a4b with SMTP id ja1-20020a170902efc100b001bc66a39a4bmr9087350plb.5.1692739852664; Tue, 22 Aug 2023 14:30:52 -0700 (PDT) Received: from tictac2.mtv.corp.google.com ([2620:15c:9d:2:83f0:2bc5:38c4:a9de]) by smtp.gmail.com with ESMTPSA id t7-20020a170902e84700b001befac3b3cbsm9451475plg.290.2023.08.22.14.30.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Aug 2023 14:30:52 -0700 (PDT) From: Douglas Anderson To: Mark Rutland , Catalin Marinas , Will Deacon , Sumit Garg , Daniel Thompson , Marc Zyngier Cc: Lecopzer Chen , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, Peter Zijlstra , kgdb-bugreport@lists.sourceforge.net, ito-yuichi@fujitsu.com, Stephen Boyd , Thomas Gleixner , Chen-Yu Tsai , Ard Biesheuvel , "Rafael J . Wysocki" , Masayoshi Mizuma , Douglas Anderson , D Scott Phillips , Ingo Molnar , Josh Poimboeuf , Valentin Schneider , linux-kernel@vger.kernel.org Subject: [PATCH v10 4/6] arm64: smp: Add arch support for backtrace using pseudo-NMI Date: Tue, 22 Aug 2023 14:26:59 -0700 Message-ID: <20230822142644.v10.4.Ie6c132b96ebbbcddbf6954b9469ed40a6960343c@changeid> X-Mailer: git-send-email 2.42.0.rc1.204.g551eb34607-goog In-Reply-To: <20230822212927.249645-1-dianders@chromium.org> References: <20230822212927.249645-1-dianders@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Enable arch_trigger_cpumask_backtrace() support on arm64. This enables things much like they are enabled on arm32 (including some of the funky logic around NR_IPI, nr_ipi, and MAX_IPI) but with the difference that, unlike arm32, we'll try to enable the backtrace to use pseudo-NMI. NOTE: this patch is a squash of the little bit of code adding the ability to mark an IPI to try to use pseudo-NMI plus the little bit of code to hook things up for kgdb. This approach was decided upon in the discussion of v9 [1]. This patch depends on commit 36759e343ff9 ("nmi_backtrace: allow excluding an arbitrary CPU") since that commit changed the prototype of arch_trigger_cpumask_backtrace(), which this patch implements. [1] https://lore.kernel.org/r/ZORY51mF4alI41G1@FVFF77S0Q05N Co-developed-by: Sumit Garg Signed-off-by: Sumit Garg Co-developed-by: Mark Rutland Signed-off-by: Mark Rutland Signed-off-by: Douglas Anderson --- Changes in v10: - Backtrace now directly supported in smp.c - Squash backtrace into patch adding support for pseudo-NMI IPIs. Changes in v9: - Added comments that we might not be using NMI always. - Fold in v8 patch #10 ("Fallback to a regular IPI if NMI isn't enabled") - Moved header file out of "include" since it didn't need to be there. - Remove arm64_supports_nmi() - Renamed "NMI IPI" to "debug IPI" since it might not be backed by NMI. - arch_trigger_cpumask_backtrace() no longer returns bool Changes in v8: - Removed "#ifdef CONFIG_SMP" since arm64 is always SMP - debug_ipi_setup() and debug_ipi_teardown() no longer take cpu param arch/arm64/include/asm/irq.h | 3 ++ arch/arm64/kernel/smp.c | 86 +++++++++++++++++++++++++++++++----- 2 files changed, 78 insertions(+), 11 deletions(-) diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h index fac08e18bcd5..50ce8b697ff3 100644 --- a/arch/arm64/include/asm/irq.h +++ b/arch/arm64/include/asm/irq.h @@ -6,6 +6,9 @@ =20 #include =20 +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu= ); +#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace + struct pt_regs; =20 int set_handle_irq(void (*handle_irq)(struct pt_regs *)); diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index bfe60adbc453..15b66dc1391b 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -33,6 +33,7 @@ #include #include #include +#include =20 #include #include @@ -72,12 +73,18 @@ enum ipi_msg_type { IPI_CPU_CRASH_STOP, IPI_TIMER, IPI_IRQ_WORK, - NR_IPI + NR_IPI, + /* + * CPU_BACKTRACE is special and not included in NR_IPI + * or tracable with trace_ipi_* + */ + IPI_CPU_BACKTRACE =3D NR_IPI, + MAX_IPI }; =20 static int ipi_irq_base __read_mostly; static int nr_ipi __read_mostly =3D NR_IPI; -static struct irq_desc *ipi_desc[NR_IPI] __read_mostly; +static struct irq_desc *ipi_desc[MAX_IPI] __read_mostly; =20 static void ipi_setup(int cpu); =20 @@ -845,6 +852,22 @@ static void __noreturn ipi_cpu_crash_stop(unsigned int= cpu, struct pt_regs *regs #endif } =20 +void arm64_backtrace_ipi(cpumask_t *mask) +{ + __ipi_send_mask(ipi_desc[IPI_CPU_BACKTRACE], mask); +} + +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu) +{ + /* + * NOTE: though nmi_trigger_cpumask_backtrace has "nmi_" in the name, + * nothing about it truly needs to be backed by an NMI, it's just that + * it's _allowed_ to work with NMIs. If ipi_should_be_nmi() returned + * false our backtrace attempt will just be backed by a regular IPI. + */ + nmi_trigger_cpumask_backtrace(mask, exclude_cpu, arm64_backtrace_ipi); +} + /* * Main handler for inter-processor interrupts */ @@ -888,6 +911,14 @@ static void do_handle_IPI(int ipinr) break; #endif =20 + case IPI_CPU_BACKTRACE: + /* + * NOTE: in some cases this _won't_ be NMI context. See the + * comment in arch_trigger_cpumask_backtrace(). + */ + nmi_cpu_backtrace(get_irq_regs()); + break; + default: pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu, ipinr); break; @@ -909,6 +940,19 @@ static void smp_cross_call(const struct cpumask *targe= t, unsigned int ipinr) __ipi_send_mask(ipi_desc[ipinr], target); } =20 +static bool ipi_should_be_nmi(enum ipi_msg_type ipi) +{ + if (!system_uses_irq_prio_masking()) + return false; + + switch (ipi) { + case IPI_CPU_BACKTRACE: + return true; + default: + return false; + } +} + static void ipi_setup(int cpu) { int i; @@ -916,8 +960,14 @@ static void ipi_setup(int cpu) if (WARN_ON_ONCE(!ipi_irq_base)) return; =20 - for (i =3D 0; i < nr_ipi; i++) - enable_percpu_irq(ipi_irq_base + i, 0); + for (i =3D 0; i < nr_ipi; i++) { + if (ipi_should_be_nmi(i)) { + prepare_percpu_nmi(ipi_irq_base + i); + enable_percpu_nmi(ipi_irq_base + i, 0); + } else { + enable_percpu_irq(ipi_irq_base + i, 0); + } + } } =20 #ifdef CONFIG_HOTPLUG_CPU @@ -928,8 +978,14 @@ static void ipi_teardown(int cpu) if (WARN_ON_ONCE(!ipi_irq_base)) return; =20 - for (i =3D 0; i < nr_ipi; i++) - disable_percpu_irq(ipi_irq_base + i); + for (i =3D 0; i < nr_ipi; i++) { + if (ipi_should_be_nmi(i)) { + disable_percpu_nmi(ipi_irq_base + i); + teardown_percpu_nmi(ipi_irq_base + i); + } else { + disable_percpu_irq(ipi_irq_base + i); + } + } } #endif =20 @@ -937,15 +993,23 @@ void __init set_smp_ipi_range(int ipi_base, int n) { int i; =20 - WARN_ON(n < NR_IPI); - nr_ipi =3D min(n, NR_IPI); + WARN_ON(n < MAX_IPI); + nr_ipi =3D min(n, MAX_IPI); =20 for (i =3D 0; i < nr_ipi; i++) { int err; =20 - err =3D request_percpu_irq(ipi_base + i, ipi_handler, - "IPI", &cpu_number); - WARN_ON(err); + if (ipi_should_be_nmi(i)) { + err =3D request_percpu_nmi(ipi_base + i, ipi_handler, + "IPI", &cpu_number); + WARN(err, "Could not request IPI %d as NMI, err=3D%d\n", + i, err); + } else { + err =3D request_percpu_irq(ipi_base + i, ipi_handler, + "IPI", &cpu_number); + WARN(err, "Could not request IPI %d as IRQ, err=3D%d\n", + i, err); + } =20 ipi_desc[i] =3D irq_to_desc(ipi_base + i); irq_set_status_flags(ipi_base + i, IRQ_HIDDEN); --=20 2.42.0.rc1.204.g551eb34607-goog