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[2620:137:e000::1:20]) by mx.google.com with ESMTP id bw11-20020a17090af60b00b0024df598ed11si1235299pjb.188.2023.05.16.02.13.22; Tue, 16 May 2023 02:13:37 -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="VIOpH//+"; 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 S232024AbjEPJML (ORCPT + 99 others); Tue, 16 May 2023 05:12:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46064 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231833AbjEPJKJ (ORCPT ); Tue, 16 May 2023 05:10:09 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B410730CF; Tue, 16 May 2023 02:10:05 -0700 (PDT) Date: Tue, 16 May 2023 09:10:01 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1684228201; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6wBjNy0QhzC5c4k+Yo6j61GyJeaXk19scg9/j8C1jOg=; b=VIOpH//+Y3G+cxTeYXybllPBEsbAXn5tIqXhFEAdkyeX7JJNlaw0ri4e4Vc42MydOO0QF1 kV6XdQaj0SIPvY4D7ExrOPo3b5PuABTN9BWzCxtZyd1HNvJ3jc3Z52MZZzDJxRMwE+TSTO q1rbIk33byr8r04I0cUWAj28F2DEUe2s/JnfDWMpGtbLPRUOrLxnqO6cVx9nl8SabC75g3 Lq6Cpe/Hg4FGqwpmQYEDfHsqOKSsSWBDs//TKf2HYxt0D3pvCe8YPMpPD4QK/wNb0C/RMM NdHJkRQlNEUGTtZIjjZ7IaR9OLSEEB1T+uWHkiRM/NqRMhN1V9/QuZ0wu579mg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1684228201; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6wBjNy0QhzC5c4k+Yo6j61GyJeaXk19scg9/j8C1jOg=; b=WbeHpHhos0HXMpIOQSXmDScjifw9wBd7PN8oq5mo4vt1cLBoiY8nak8VtXTD2rEm/kjbMC BB3112IVjutq/RCg== From: "tip-bot2 for David Woodhouse" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: smp/core] x86/smpboot: Split up native_cpu_up() into separate phases and document them Cc: David Woodhouse , Thomas Gleixner , "Peter Zijlstra (Intel)" , Michael Kelley , Oleksandr Natalenko , Helge Deller , "Guilherme G. Piccoli" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20230512205255.928917242@linutronix.de> References: <20230512205255.928917242@linutronix.de> MIME-Version: 1.0 Message-ID: <168422820143.404.13560799780952471120.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails 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?1765724798831558175?= X-GMAIL-MSGID: =?utf-8?q?1766041496942062400?= The following commit has been merged into the smp/core branch of tip: Commit-ID: 2b3be65d2e4f4bb9358b039b99ad1a391dd3c311 Gitweb: https://git.kernel.org/tip/2b3be65d2e4f4bb9358b039b99ad1a391dd3c311 Author: David Woodhouse AuthorDate: Fri, 12 May 2023 23:07:11 +02:00 Committer: Peter Zijlstra CommitterDate: Mon, 15 May 2023 13:44:51 +02:00 x86/smpboot: Split up native_cpu_up() into separate phases and document them 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 Signed-off-by: Peter Zijlstra (Intel) Tested-by: Michael Kelley Tested-by: Oleksandr Natalenko Tested-by: Helge Deller # parisc Tested-by: Guilherme G. Piccoli # Steam Deck Link: https://lore.kernel.org/r/20230512205255.928917242@linutronix.de --- arch/x86/kernel/smpboot.c | 184 +++++++++++++++++++++++-------------- 1 file changed, 119 insertions(+), 65 deletions(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index f5f4328..0bd9c9f 100644 --- 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. + */ notify_cpu_starting(cpuid); /* @@ -233,12 +237,28 @@ static void notrace start_secondary(void *unused) 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(); - /* 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(); /* @@ -257,6 +277,7 @@ static void notrace start_secondary(void *unused) * 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(); @@ -979,17 +1000,13 @@ int common_cpu_up(unsigned int cpu, struct task_struct *idle) /* * 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) @@ -1046,60 +1063,89 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle) * - 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(); @@ -1140,25 +1186,33 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle) 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; } /**