From patchwork Thu May 4 19:02:11 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Gleixner X-Patchwork-Id: 90181 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b0ea:0:b0:3b6:4342:cba0 with SMTP id b10csp544035vqo; Thu, 4 May 2023 12:04:10 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ6dGDcvNbwylNyoB2c8UG2SDMQ16OaL4fRmb0L5JmeUacZOMRwZULVJNl2ow6tJXDr407VW X-Received: by 2002:a05:6a20:9f49:b0:db:f682:65ed with SMTP id ml9-20020a056a209f4900b000dbf68265edmr3288774pzb.61.1683227050475; Thu, 04 May 2023 12:04:10 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1683227050; cv=none; d=google.com; s=arc-20160816; b=IF6pk26e/qtzmIF31hHz0HVQkDDBfDcZpA+3+cvKmci6eOh3xCKuj+vKPhLLnXXU/3 BNIqnNNqdUZN/uBwVRiGRxH46NYUNq36+MHA8sJbsYV+CeqItx4z+g//iLtfF/NUuKg1 WqvhldKMnI8gz4UcSwwxPDvN/8hJr4HS0aDZeXel2AFjvz9K5pr74E5F+NN1Q/G9ynu8 TIUY+gqbrqKf8spI70yUyhsFDukFgzDuIwkKT/qzoIIRQHBiB9dUv+S3GaRLNONZ9CLw XPF/UggjMXxoXUVCCP9LCu7HE0tKEFEGvd2pj/aS8l8ZR9p595aYzGjE9FESVt87lLtl ejSg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:date:mime-version:references:subject:cc:to:from :dkim-signature:dkim-signature:message-id; bh=Csk76nlugXhAU996VRssrwo8MVI1hAOPsGe3TXuIETM=; b=odSEvtdDXorRzdqosykuqktmloI794VnYaXaHRH/ESr8FGGIHPhEoqGoCazGVlDi9z 1UptD/mkqR6FP7wBGUB9eKU7t3YXLYij/c00ZQsyJXLjxfoGrRgQftoEAouRscWwt5S0 FY01VQ0d/PMtjWZP5E2KWAZkEsapGvnmnCtnM9aVXscYQmfffTMiB/juFkjj2Nfz1M9f qAZXD+Iy1QlRVAfBzAj/T2ujXYT6xv+g83mdPmavjPtjDiX0LJ4k4ZecSbv70bTRnprB uysxMlCGtdw7N3W4gQ6nDE/woiA4Oae9PXyNUdJ8u/wJS/laI8Chbbi0SQrFV15yJsOR dh2w== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b=tpY2Pta1; dkim=neutral (no key) header.i=@linutronix.de; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id k186-20020a633dc3000000b0051ba16c35c9si143388pga.155.2023.05.04.12.03.55; Thu, 04 May 2023 12:04:10 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b=tpY2Pta1; dkim=neutral (no key) header.i=@linutronix.de; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229671AbjEDTCx (ORCPT + 99 others); Thu, 4 May 2023 15:02:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229990AbjEDTCb (ORCPT ); Thu, 4 May 2023 15:02:31 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A0C5883CF; Thu, 4 May 2023 12:02:13 -0700 (PDT) Message-ID: <20230504185936.750150196@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1683226932; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=Csk76nlugXhAU996VRssrwo8MVI1hAOPsGe3TXuIETM=; b=tpY2Pta11o5D+EBlLezP7+DQ0YHNLnnshfEKyGamHfMkSJSDc6pWd24jta33cQ6549e5n0 YoCRhsqkaZ0RzkSEFfE53xlP/wOrJKVGfAasd+i1K8FwsOnit2R8Qcbst29P+dph3dRJkn MWH3Lq9LgxU+JESzbQnOULIN1Fs0BetdOgLMsOeCIiVyyZnbX0XyK/efLbSuRFMNnGI3x6 cKRhbBjsP/glATrekoMoT4u4F+Pv2ebV/PeVUxNrAcjRy4EL78zxGMHmgOH903YOe9OGR3 DTNVfbTo3Z9BrgHrkycf+LctlaGconOxbeHGZGJUplx9zbo/SySM8/Japzc/+Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1683226932; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: references:references; bh=Csk76nlugXhAU996VRssrwo8MVI1hAOPsGe3TXuIETM=; b=7clF0BS88qjmoiBaLOkVsFT638/SjDAHfzIc/R9HEwJjRQD5/6IkcSs7vkFzJfGoR95jo3 dYaej/CZ6HDpvPAA== From: Thomas Gleixner To: LKML Cc: x86@kernel.org, David Woodhouse , Andrew Cooper , Brian Gerst , Arjan van de Veen , Paolo Bonzini , Paul McKenney , Tom Lendacky , Sean Christopherson , Oleksandr Natalenko , Paul Menzel , "Guilherme G. Piccoli" , Piotr Gorski , Usama Arif , Juergen Gross , Boris Ostrovsky , xen-devel@lists.xenproject.org, Russell King , Arnd Bergmann , linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon , Guo Ren , linux-csky@vger.kernel.org, Thomas Bogendoerfer , linux-mips@vger.kernel.org, "James E.J. Bottomley" , Helge Deller , linux-parisc@vger.kernel.org, Paul Walmsley , Palmer Dabbelt , linux-riscv@lists.infradead.org, Mark Rutland , Sabin Rapan , "Michael Kelley (LINUX)" , David Woodhouse Subject: [patch V2 08/38] x86/smpboot: Split up native_cpu_up() into separate phases and document them References: <20230504185733.126511787@linutronix.de> MIME-Version: 1.0 Date: Thu, 4 May 2023 21:02:11 +0200 (CEST) X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1764991487548391301?= X-GMAIL-MSGID: =?utf-8?q?1764991487548391301?= From: David Woodhouse There are four logical parts to what native_cpu_up() does on the BSP (or on the controlling CPU for a later hotplug): 1) Wake the AP by sending the INIT/SIPI/SIPI sequence. 2) Wait for the AP to make it as far as wait_for_master_cpu() which sets that CPU's bit in cpu_initialized_mask, then sets the bit in cpu_callout_mask to let the AP proceed through cpu_init(). 3) Wait for the AP to finish cpu_init() and get as far as the smp_callin() call, which sets that CPU's bit in cpu_callin_mask. 4) Perform the TSC synchronization and wait for the AP to actually mark itself online in cpu_online_mask. In preparation to allow these phases to operate in parallel on multiple APs, split them out into separate functions and document the interactions a little more clearly in both the BP and AP code paths. No functional change intended. Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner --- arch/x86/kernel/smpboot.c | 187 +++++++++++++++++++++++++++++----------------- 1 file changed, 121 insertions(+), 66 deletions(-) --- --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -193,6 +193,10 @@ static void smp_callin(void) wmb(); + /* + * This runs the AP through all the cpuhp states to its target + * state (CPUHP_ONLINE in the case of serial bringup). + */ notify_cpu_starting(cpuid); /* @@ -233,14 +237,31 @@ static void notrace start_secondary(void load_cr3(swapper_pg_dir); __flush_tlb_all(); #endif + /* + * Sync point with wait_cpu_initialized(). Before proceeding through + * cpu_init(), the AP will call wait_for_master_cpu() which sets its + * own bit in cpu_initialized_mask and then waits for the BSP to set + * its bit in cpu_callout_mask to release it. + */ cpu_init_secondary(); rcu_cpu_starting(raw_smp_processor_id()); x86_cpuinit.early_percpu_clock_init(); + + /* + * Sync point with wait_cpu_callin(). The AP doesn't wait here + * but just sets the bit to let the controlling CPU (BSP) know that + * it's got this far. + */ smp_callin(); - /* otherwise gcc will move up smp_processor_id before the cpu_init */ + /* Otherwise gcc will move up smp_processor_id() before cpu_init() */ barrier(); - /* Check TSC synchronization with the control CPU: */ + + /* + * Check TSC synchronization with the control CPU, which will do + * its part of this from wait_cpu_online(), making it an implicit + * synchronization point. + */ check_tsc_sync_target(); /* @@ -259,6 +280,7 @@ static void notrace start_secondary(void * half valid vector space. */ lock_vector_lock(); + /* Sync point with do_wait_cpu_online() */ set_cpu_online(smp_processor_id(), true); lapic_online(); unlock_vector_lock(); @@ -981,17 +1003,13 @@ int common_cpu_up(unsigned int cpu, stru /* * NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad * (ie clustered apic addressing mode), this is a LOGICAL apic ID. - * Returns zero if CPU booted OK, else error code from + * Returns zero if startup was successfully sent, else error code from * ->wakeup_secondary_cpu. */ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle) { - /* start_ip had better be page-aligned! */ unsigned long start_ip = real_mode_header->trampoline_start; - unsigned long boot_error = 0; - unsigned long timeout; - #ifdef CONFIG_X86_64 /* If 64-bit wakeup method exists, use the 64-bit mode trampoline IP */ if (apic->wakeup_secondary_cpu_64) @@ -1048,60 +1066,89 @@ static int do_boot_cpu(int apicid, int c * - Use an INIT boot APIC message */ if (apic->wakeup_secondary_cpu_64) - boot_error = apic->wakeup_secondary_cpu_64(apicid, start_ip); + return apic->wakeup_secondary_cpu_64(apicid, start_ip); else if (apic->wakeup_secondary_cpu) - boot_error = apic->wakeup_secondary_cpu(apicid, start_ip); - else - boot_error = wakeup_secondary_cpu_via_init(apicid, start_ip); + return apic->wakeup_secondary_cpu(apicid, start_ip); - if (!boot_error) { - /* - * Wait 10s total for first sign of life from AP - */ - boot_error = -1; - timeout = jiffies + 10*HZ; - while (time_before(jiffies, timeout)) { - if (cpumask_test_cpu(cpu, cpu_initialized_mask)) { - /* - * Tell AP to proceed with initialization - */ - cpumask_set_cpu(cpu, cpu_callout_mask); - boot_error = 0; - break; - } - schedule(); - } - } + return wakeup_secondary_cpu_via_init(apicid, start_ip); +} - if (!boot_error) { - /* - * Wait till AP completes initial initialization - */ - while (!cpumask_test_cpu(cpu, cpu_callin_mask)) { - /* - * Allow other tasks to run while we wait for the - * AP to come online. This also gives a chance - * for the MTRR work(triggered by the AP coming online) - * to be completed in the stop machine context. - */ - schedule(); - } - } +static int wait_cpu_cpumask(unsigned int cpu, const struct cpumask *mask) +{ + unsigned long timeout; - if (x86_platform.legacy.warm_reset) { - /* - * Cleanup possible dangling ends... - */ - smpboot_restore_warm_reset_vector(); + /* + * Wait up to 10s for the CPU to report in. + */ + timeout = jiffies + 10*HZ; + while (time_before(jiffies, timeout)) { + if (cpumask_test_cpu(cpu, mask)) + return 0; + + schedule(); } + return -1; +} - return boot_error; +/* + * Bringup step two: Wait for the target AP to reach cpu_init_secondary() + * and thus wait_for_master_cpu(), then set cpu_callout_mask to allow it + * to proceed. The AP will then proceed past setting its 'callin' bit + * and end up waiting in check_tsc_sync_target() until we reach + * do_wait_cpu_online() to tend to it. + */ +static int wait_cpu_initialized(unsigned int cpu) +{ + /* + * Wait for first sign of life from AP. + */ + if (wait_cpu_cpumask(cpu, cpu_initialized_mask)) + return -1; + + cpumask_set_cpu(cpu, cpu_callout_mask); + return 0; } -int native_cpu_up(unsigned int cpu, struct task_struct *tidle) +/* + * Bringup step three: Wait for the target AP to reach smp_callin(). + * The AP is not waiting for us here so we don't need to parallelise + * this step. Not entirely clear why we care about this, since we just + * proceed directly to TSC synchronization which is the next sync + * point with the AP anyway. + */ +static void wait_cpu_callin(unsigned int cpu) +{ + while (!cpumask_test_cpu(cpu, cpu_callin_mask)) + schedule(); +} + +/* + * Bringup step four: Synchronize the TSC and wait for the target AP + * to reach set_cpu_online() in start_secondary(). + */ +static void wait_cpu_online(unsigned int cpu) { - int apicid = apic->cpu_present_to_apicid(cpu); unsigned long flags; + + /* + * Check TSC synchronization with the AP (keep irqs disabled + * while doing so): + */ + local_irq_save(flags); + check_tsc_sync_source(cpu); + local_irq_restore(flags); + + /* + * Wait for the AP to mark itself online, so the core caller + * can drop sparse_irq_lock. + */ + while (!cpu_online(cpu)) + schedule(); +} + +static int native_kick_ap(unsigned int cpu, struct task_struct *tidle) +{ + int apicid = apic->cpu_present_to_apicid(cpu); int err; lockdep_assert_irqs_enabled(); @@ -1142,25 +1189,33 @@ int native_cpu_up(unsigned int cpu, stru return err; err = do_boot_cpu(apicid, cpu, tidle); - if (err) { + if (err) pr_err("do_boot_cpu failed(%d) to wakeup CPU#%u\n", err, cpu); - return err; - } - /* - * Check TSC synchronization with the AP (keep irqs disabled - * while doing so): - */ - local_irq_save(flags); - check_tsc_sync_source(cpu); - local_irq_restore(flags); + return err; +} - while (!cpu_online(cpu)) { - cpu_relax(); - touch_nmi_watchdog(); - } +int native_cpu_up(unsigned int cpu, struct task_struct *tidle) +{ + int ret; - return 0; + ret = native_kick_ap(cpu, tidle); + if (ret) + goto out; + + ret = wait_cpu_initialized(cpu); + if (ret) + goto out; + + wait_cpu_callin(cpu); + wait_cpu_online(cpu); + +out: + /* Cleanup possible dangling ends... */ + if (x86_platform.legacy.warm_reset) + smpboot_restore_warm_reset_vector(); + + return ret; } /**