From patchwork Wed Mar 24 15:22:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vitaly Kuznetsov X-Patchwork-Id: 12161621 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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 78137C433C1 for ; Wed, 24 Mar 2021 15:23:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43F16619EE for ; Wed, 24 Mar 2021 15:23:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236565AbhCXPXZ (ORCPT ); Wed, 24 Mar 2021 11:23:25 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:57205 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236644AbhCXPW7 (ORCPT ); Wed, 24 Mar 2021 11:22:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616599379; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=9vmQn4NIrUk8xJdGGejNzI5lmYgeNFGUq43EqQoEUhA=; b=J0+nJEAbPhqkWU3c7dGWTs6imgT/NPwyAnWC7uqct2+OOhk1nZzq3h1SXN4O+gLuHysJ1U 0gO88eoEcJWwNAkTlgado8lT97g8xGw4LJgf03bqn4xX0jhwDBUqS3u5D/3lS1nRAtw+wr m/AnpEP2RcRDmWMZn5EcRxWCCmFVm4Q= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-172-7gABUynXOzW75-OE2il27A-1; Wed, 24 Mar 2021 11:22:54 -0400 X-MC-Unique: 7gABUynXOzW75-OE2il27A-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7CF57884D97; Wed, 24 Mar 2021 15:22:24 +0000 (UTC) Received: from vitty.brq.redhat.com (unknown [10.40.195.59]) by smtp.corp.redhat.com (Postfix) with ESMTP id C49E6E169; Wed, 24 Mar 2021 15:22:20 +0000 (UTC) From: Vitaly Kuznetsov To: linux-acpi@vger.kernel.org, x86@kernel.org Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , "Rafael J. Wysocki" , Len Brown , "Peter Zijlstra (Intel)" , Al Stone , Zhang Rui , linux-kernel@vger.kernel.org Subject: [PATCH] ACPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead() Date: Wed, 24 Mar 2021 16:22:19 +0100 Message-Id: <20210324152219.1456012-1-vkuznets@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org Commit 496121c02127 ("ACPI: processor: idle: Allow probing on platforms with one ACPI C-state") broke CPU0 hotplug on certain systems, e.g. I'm observing the following on AWS Nitro (e.g r5b.xlarge but other instance types are affected as well): # echo 0 > /sys/devices/system/cpu/cpu0/online # echo 1 > /sys/devices/system/cpu/cpu0/online <10 seconds delay> -bash: echo: write error: Input/output error In fact, the above mentioned commit only revealed the problem and did not introduce it. On x86, to wakeup CPU an NMI is being used and hlt_play_dead()/mwait_play_dead() loops are prepared to handle it: /* * If NMI wants to wake up CPU0, start CPU0. */ if (wakeup_cpu0()) start_cpu0(); cpuidle_play_dead() -> acpi_idle_play_dead() (which is now being called on systems where it wasn't called before the above mentioned commit) serves the same purpose but it doesn't have a path for CPU0. What happens now on wakeup is: - NMI is sent to CPU0 - wakeup_cpu0_nmi() works as expected - we get back to while (1) loop in acpi_idle_play_dead() - safe_halt() puts CPU0 to sleep again. The straightforward/minimal fix is add the special handling for CPU0 on x86 and that's what the patch is doing. Fixes: 496121c02127 ("ACPI: processor: idle: Allow probing on platforms with one ACPI C-state") Signed-off-by: Vitaly Kuznetsov --- arch/x86/include/asm/smp.h | 1 + arch/x86/kernel/smpboot.c | 2 +- drivers/acpi/processor_idle.c | 7 +++++++ 3 files changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h index c0538f82c9a2..57ef2094af93 100644 --- a/arch/x86/include/asm/smp.h +++ b/arch/x86/include/asm/smp.h @@ -132,6 +132,7 @@ void native_play_dead(void); void play_dead_common(void); void wbinvd_on_cpu(int cpu); int wbinvd_on_all_cpus(void); +bool wakeup_cpu0(void); void native_smp_send_reschedule(int cpu); void native_send_call_func_ipi(const struct cpumask *mask); diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 02813a7f3a7c..f877150a91da 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1659,7 +1659,7 @@ void play_dead_common(void) local_irq_disable(); } -static bool wakeup_cpu0(void) +bool wakeup_cpu0(void) { if (smp_processor_id() == 0 && enable_start_cpu0) return true; diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index d93e400940a3..eb1101b16c08 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -29,6 +29,7 @@ */ #ifdef CONFIG_X86 #include +#include #endif #define _COMPONENT ACPI_PROCESSOR_COMPONENT @@ -541,6 +542,12 @@ static int acpi_idle_play_dead(struct cpuidle_device *dev, int index) wait_for_freeze(); } else return -ENODEV; + +#ifdef CONFIG_X86 + /* If NMI wants to wake up CPU0, start CPU0. */ + if (wakeup_cpu0()) + start_cpu0(); +#endif } /* Never reached */