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: 13231832 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D1DBFC77B7C for ; Thu, 4 May 2023 21:16:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Date:MIME-Version:References:Subject:Cc :To:From:Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To: List-Owner; bh=5WDZv1QXQhN1NrZNK7eXFyzjtNFXpQHbU5C9/YMTmQw=; b=tExSjfw2F+j7Qu Uqpy0sLvqQJLlDHig+kWNkIo5LqYS83W2mDSJlnN1stfw9EUmqfaEPkn9rpbFAUqSq3kc9++NYBiF uKXRIjiSKSK/n2XUlQD+kWCf2GHh9ss9Cp/PVOqECYAznQ/kjKyDWEwYs+OvdzKUh+ephIS+FW5nT gisB4i4cSrIV+UTq2VXvefqwAW6S30MRIrIVf+VQJ7PBDNDfcNkF6Qr9ty8R6nyPFfE9fKH0vmbh1 D463mTMZonSIlyhbqf0e3ynx4zxw/DyjOzshZaavgIiEfe6fKAlTw0J61SVBxIC/QKZVP5SpL9KCE 1gHWVv3TY2ZrsPg/cmZQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pugIo-0090xh-2G; Thu, 04 May 2023 21:15:50 +0000 Received: from galois.linutronix.de ([193.142.43.55]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1pueDV-008dIT-15; Thu, 04 May 2023 19:02:17 +0000 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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230504_120213_699608_88EFB36D X-CRM114-Status: GOOD ( 25.02 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org 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; } /**