From mboxrd@z Thu Jan 1 00:00:00 1970 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=-15.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 C2AC9C04FF3 for ; Mon, 24 May 2021 06:40:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9145461139 for ; Mon, 24 May 2021 06:40:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232286AbhEXGmN (ORCPT ); Mon, 24 May 2021 02:42:13 -0400 Received: from mail-eopbgr10086.outbound.protection.outlook.com ([40.107.1.86]:39495 "EHLO EUR02-HE1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S232120AbhEXGmL (ORCPT ); Mon, 24 May 2021 02:42:11 -0400 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=K1wISudJrtUVKZPX2AIO7Z+glkxpY8mRsIY+wtup7FLvpsUokrDd3Hv/bHJSqfabP6v8wrN0cRqTV2ndlH39uEnGJfHzrjNTwJlhBG9mCzANB061MIKW2qs+7VEhO/0gWhw6wtwKVrMSK/apOwIks4Mdp1lOb3LiXceWmn7ZMhAQya6YKjUFQyTGvivIUlqzbQVcY7yuM4TbUa+b9LPxOyXd0OjjF6S5r4pBhzE5Fk6AwiAIVq4P5pC77LUpfIdQI4IGLvJtcH4pUHB6GLhWXJ1bZcCS1YIW6LA0LfUv6riXrwz/1iKuvtcnutv6JANZ9Xk3ExxFjFoUUicKyV4WTg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=nHL6h2owE7x03SmmTXD+ACp5oHnHEKET4bmBchK4gi4=; b=QzYxYjpBuiidsnRLUYsk06cNUoUn77h4zsLzhgQQh0NUJamXfMQlI9YJ12nSvoPaWBl4gDPxlUnVNzpWN6GAoMKGGrn4rcWOYcpzk6fr9Sb85CbVznRcWHXOJ29q+Pujv0wjUkBWbozYff2lKVYGP8lF9moKrpvN91XLoiu/rWipV4sVODDRaHcjDtViWtRVU+WMJ5j3NXYzAjcZ1j1u7XPzyqy4jd4dv2j7WdV40EIDlrNTDV8hnIuJcU1Ka742Dw9ZNSsmV9bDoGui+b61ZigM43M1THLoooCHoy7eQLc7/HmbKfrW4CH6XsFLO6UVe2KZyWhpVzVB3hIvn0z8Mw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nextfour.com; dmarc=pass action=none header.from=nextfour.com; dkim=pass header.d=nextfour.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=NextfourGroupOy.onmicrosoft.com; s=selector2-NextfourGroupOy-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=nHL6h2owE7x03SmmTXD+ACp5oHnHEKET4bmBchK4gi4=; b=rkA61Gx/D4xeWcrZpTomx3bhPcfJAAXNG5J+5m2DXrrHRJRN0l5naE/qICmVxKNM27+gHR3T+UYjH7BAobQ5ZuJaXmMwPi+sZfLC79OIlrSgi90p//tfG1Wbt5YFQAsGfo0VAd3n9rDhvKWNT3bQMEMIScSQ+2/onGZWxjtFFPE= Authentication-Results: vger.kernel.org; dkim=none (message not signed) header.d=none;vger.kernel.org; dmarc=none action=none header.from=nextfour.com; Received: from DBAPR03MB6630.eurprd03.prod.outlook.com (2603:10a6:10:194::6) by DB8PR03MB5546.eurprd03.prod.outlook.com (2603:10a6:10:106::33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4150.25; Mon, 24 May 2021 06:40:41 +0000 Received: from DBAPR03MB6630.eurprd03.prod.outlook.com ([fe80::593:3329:e104:239]) by DBAPR03MB6630.eurprd03.prod.outlook.com ([fe80::593:3329:e104:239%5]) with mapi id 15.20.4150.027; Mon, 24 May 2021 06:40:41 +0000 Subject: Re: [PATCH v5 1/1] x86/acpi, x86/boot: Add multiprocessor wake-up support To: Kuppuswamy Sathyanarayanan , Rafael J Wysocki , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Peter Zijlstra Cc: Len Brown , Kuppuswamy Sathyanarayanan , Sean Christopherson , Andi Kleen , x86@kernel.org, linux-kernel@vger.kernel.org References: <20210524060221.519093-1-sathyanarayanan.kuppuswamy@linux.intel.com> From: =?UTF-8?Q?Mika_Penttil=c3=a4?= Message-ID: <4295dab3-7675-9146-ac6e-244704ecfcca@nextfour.com> Date: Mon, 24 May 2021 09:40:38 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 In-Reply-To: <20210524060221.519093-1-sathyanarayanan.kuppuswamy@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [91.145.109.188] X-ClientProxiedBy: HE1PR08CA0052.eurprd08.prod.outlook.com (2603:10a6:7:2a::23) To DBAPR03MB6630.eurprd03.prod.outlook.com (2603:10a6:10:194::6) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.1.121] (91.145.109.188) by HE1PR08CA0052.eurprd08.prod.outlook.com (2603:10a6:7:2a::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4150.27 via Frontend Transport; Mon, 24 May 2021 06:40:40 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 5a67a86a-73d4-4d9b-206b-08d91e7ed93a X-MS-TrafficTypeDiagnostic: DB8PR03MB5546: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:6790; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DBAPR03MB6630.eurprd03.prod.outlook.com;PTR:;CAT:NONE;SFS:(346002)(396003)(376002)(366004)(39830400003)(136003)(2906002)(5660300002)(6486002)(86362001)(66476007)(31696002)(54906003)(110136005)(66556008)(7416002)(16576012)(4326008)(8936002)(186003)(31686004)(478600001)(316002)(8676002)(83380400001)(38350700002)(38100700002)(36756003)(52116002)(16526019)(956004)(2616005)(66946007)(26005)(21314003)(45980500001)(43740500002);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?cUxPSHBScmxSa1AreDh1WjA2Y1lWL0wwTnBsT0lKTkd4K1p3ZTNmekdrU29q?= =?utf-8?B?WFNDaDRKWTF0bk1hREhqVG9sOFRWcmY4cDBKVlJCTlU5R213cHNHRXdTR0kw?= =?utf-8?B?aUtzRGFyeS9FcWZ2bWRLVW5WTitzWmhIS2oxSVlSbTMrcVFhanczTFVZMXJZ?= =?utf-8?B?U2FPenlpTkp3L05tZnFUbjd1ZVI5bHF5QVZmVzc2OU5nTmNkVW9zb3l5Y3RU?= =?utf-8?B?UFlBbFlybnJtTEtqU3hSSkdyV3NYVnZxRlM3Kys4ZnJoaXpWZzZ6eHNjRXg4?= =?utf-8?B?MVNJak1oMG9mVDluR2ZyWWY3ZnUvUTFOR25LbDVvMisyM2pCbVRtMUVpZVc1?= =?utf-8?B?eDRUVUZPdlFLUEJUNDUwQU9Od2NKajZBSTRlOUlTVW1TUjVuWlJxdEFGUUpy?= =?utf-8?B?MVVBRGx5clZCUFVldHNrM1VVdlE3VkkrMzUybGRpenJxRlU0OEdPSlFPdEdI?= =?utf-8?B?bjh5QmloTGFlVUxMdzdnVzZTUlFXWGpUdFNGa3hjdjRnYmN3c0NHK0R0dlVF?= =?utf-8?B?a2pvTXZoemhyc3FWN3RCS00yQXo5a2Qyc3RSamc1YWk4UkVxTVZhckJkb0JS?= =?utf-8?B?WnNQRHVvempvUGpnUThlTG5aaUp3NXZZd2xiZ1RJNmxVYnJ6T1YxdFNJOGdy?= =?utf-8?B?Ynd5NWo5RnRlbnlTQ0Z1RUZaSGx2U2VNYkMyaWwxVnpiT2szOHJZT3dCMUNV?= =?utf-8?B?Ni9oUm1vSEVrUlU4VmRyRFRJS2puZjg5UW00NTZDZTlpZzVGdDJiTEZpSmhU?= =?utf-8?B?aFk4bTBQZU5hdDVpcHRDOFRsVkErdWJVTTg3NlRlZ1h0Y3JZaXlNZUl4RE9h?= =?utf-8?B?SzlZT0ROc2ZkVm04NHlwcXpvZ2ZXZEE1RjYzR1QrK3dtVUlzSXoyV0NsYVV1?= =?utf-8?B?VFRMVjc2TW5zSCtEdzdiYnRUelRtZTUyWFNmRElIdlNEWWJ1VDdjMmJTbXJH?= =?utf-8?B?ckI1Z1RvRWNZcURja0QwS1VVZGxXdW1lS3VrQlNDNnBnSVNhRENnOEUrU2pa?= =?utf-8?B?bWgrUU1XaUdkaXZTa1BGeDhnSzY1MGVyQUV5dkNxQmxGZTJRR3pCQ0pNY2lS?= =?utf-8?B?a3owTlJra0tlYkFwQWdoblF4cTZSYUhUd2sxYUM1aTFWSGtPUFJLWHZWZUVV?= =?utf-8?B?Tkl1aGdudTZ0L1kzWUpxKzJ1VDQ0TFEwTTAwNHdtMmUxb2IrUVVUcWJ6citF?= =?utf-8?B?akRUeUZvcmxMeG9VYnNjM1lhZGJhL2pnT0FBS2RRbGlnNFRZZTRXT3ZjVzFr?= =?utf-8?B?dTdOSm1SVEgvc3ZTZm81QTZTRWdzemVYWTdKVUxVYlNKanprTTJWdEZQRDV1?= =?utf-8?B?dHZmSTFYaG1uRnRnL2srWjBRV0dVcjdPV0c4djhrd0twVFIrK0hMVmZBYXY4?= =?utf-8?B?QU1MZ1k0K1RsQUJEbmNkcmpFS04vZjhZUmIxZjYrQWx0aEJITmNaNUJZbmp6?= =?utf-8?B?THROUEtLaEZ0MDR6T1Z2Zm10VUF2UmJlTlFmZG5tcHFmbGVqZFdRRU1ZdmpE?= =?utf-8?B?L3YwRE8zNWFienRtaUdUa3BIVCtCcHdUYlVWeXhKdnYxaXJxcG1RUnArNEcz?= =?utf-8?B?dWFrS3h1ZklKWmM1TW4yOUgvdVN3Q0VTaHNwNThnMlI5MnBaWHUwWGxVYmZI?= =?utf-8?B?YzVJWHIwODZoZGVoeHpIdzhwSjZzK3J3aGtFeWFzbE9IbVRXVGNtTXozWHA0?= =?utf-8?B?VnNEaGQ5Ry9WNmYzeUxhckRQOVEvTUh3V3BZRXNKUkprYnpDQlIzT3dGNVBR?= =?utf-8?Q?PT+fU868/MyoExIA4+t7V2tFryc2pVCYYBsTbtJ?= X-OriginatorOrg: nextfour.com X-MS-Exchange-CrossTenant-Network-Message-Id: 5a67a86a-73d4-4d9b-206b-08d91e7ed93a X-MS-Exchange-CrossTenant-AuthSource: DBAPR03MB6630.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 May 2021 06:40:41.1621 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 972e95c2-9290-4a02-8705-4014700ea294 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: E27MdDJdkE0BytmOKSlpcljJ1RelJ8KWqlgEXHvxcUPjx+/MF22DRBPFe34j3m7suAU4+NREVct7Dr9GopbGVLJ4cNbaCkDQdcuMJ1AKN1Y= X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB8PR03MB5546 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24.5.2021 9.02, Kuppuswamy Sathyanarayanan wrote: > As per ACPI specification r6.4, sec 5.2.12.19, a new sub > structure – multiprocessor wake-up structure - is added to the > ACPI Multiple APIC Description Table (MADT) to describe the > information of the mailbox. If a platform firmware produces the > multiprocessor wake-up structure, then OS may use this new > mailbox-based mechanism to wake up the APs. > > Add ACPI MADT wake table parsing support for x86 platform and if > MADT wake table is present, update apic->wakeup_secondary_cpu with > new API which uses MADT wake mailbox to wake-up CPU. > > Co-developed-by: Sean Christopherson > Signed-off-by: Sean Christopherson > Signed-off-by: Kuppuswamy Sathyanarayanan > Reviewed-by: Andi Kleen > --- > > Changes since v4: > * Used smp_store_release() in place of WRITE_ONCE(). > * Addressed some checkpatch warnings. > > Changes since v3: > * Removed acpi_mp_wake_mailbox_init() and moved init code to > acpi_wakeup_cpu(). > * Removed redundant NULL pointer check for acpi_mp_wake_mailbox. > * Added comments/debug prints as per Rafael's suggestion. > * Removed MADT/SVKL ACPI patches from this patchset. It will be > merged via ACPICA submission. > > arch/x86/include/asm/apic.h | 3 ++ > arch/x86/kernel/acpi/boot.c | 96 +++++++++++++++++++++++++++++++++++++ > arch/x86/kernel/apic/apic.c | 8 ++++ > 3 files changed, 107 insertions(+) > > diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h > index 412b51e059c8..3e94e1f402ea 100644 > --- a/arch/x86/include/asm/apic.h > +++ b/arch/x86/include/asm/apic.h > @@ -487,6 +487,9 @@ static inline unsigned int read_apic_id(void) > return apic->get_apic_id(reg); > } > > +typedef int (*wakeup_cpu_handler)(int apicid, unsigned long start_eip); > +extern void acpi_wake_cpu_handler_update(wakeup_cpu_handler handler); > + > extern int default_apic_id_valid(u32 apicid); > extern int default_acpi_madt_oem_check(char *, char *); > extern void default_setup_apic_routing(void); > diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c > index 14cd3186dc77..c51134eb55d0 100644 > --- a/arch/x86/kernel/acpi/boot.c > +++ b/arch/x86/kernel/acpi/boot.c > @@ -65,6 +65,10 @@ int acpi_fix_pin2_polarity __initdata; > static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE; > #endif > > +static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox; > +static u64 acpi_mp_wake_mailbox_paddr; > +static physid_mask_t apic_id_wakemap = PHYSID_MASK_NONE; > + > #ifdef CONFIG_X86_IO_APIC > /* > * Locks related to IOAPIC hotplug > @@ -329,6 +333,68 @@ acpi_parse_lapic_nmi(union acpi_subtable_headers * header, const unsigned long e > return 0; > } > So this isn't supporting suspend/resume if AP cannot started again? > +static int acpi_wakeup_cpu(int apicid, unsigned long start_ip) > +{ > + u8 timeout = 0xFF; > + > + /* Remap mailbox memory only for the first call to acpi_wakeup_cpu() */ > + if (physids_empty(apic_id_wakemap)) { > + acpi_mp_wake_mailbox = memremap(acpi_mp_wake_mailbox_paddr, > + sizeof(*acpi_mp_wake_mailbox), > + MEMREMAP_WB); > + } > + > + /* > + * According to the ACPI specification r6.4, sec 5.2.12.19, the > + * mailbox-based wakeup mechanism cannot be used more than once > + * for the same CPU, so skip sending wake commands to already > + * awake CPU. > + */ > + if (physid_isset(apicid, apic_id_wakemap)) { > + pr_err("CPU already awake (APIC ID %x), skipping wakeup\n", > + apicid); > + return -EINVAL; > + } > + > + /* > + * Mailbox memory is shared between firmware and OS. Firmware will > + * listen on mailbox command address, and once it receives the wakeup > + * command, CPU associated with the given apicid will be booted. So, > + * the value of apic_id and wakeup_vector has to be set before updating > + * the wakeup command. So use smp_store_release to let the compiler know > + * about it and preserve the order of writes. > + */ > + smp_store_release(&acpi_mp_wake_mailbox->apic_id, apicid); > + smp_store_release(&acpi_mp_wake_mailbox->wakeup_vector, start_ip); > + smp_store_release(&acpi_mp_wake_mailbox->command, > + ACPI_MP_WAKE_COMMAND_WAKEUP); > + > + /* > + * After writing wakeup command, wait for maximum timeout of 0xFF > + * for firmware to reset the command address back zero to indicate > + * the successful reception of command. > + * NOTE: 255 as timeout value is decided based on our experiments. > + * > + * XXX: Change the timeout once ACPI specification comes up with > + * standard maximum timeout value. > + */ > + while (READ_ONCE(acpi_mp_wake_mailbox->command) && timeout--) > + cpu_relax(); > + > + if (timeout) { > + /* > + * If the CPU wakeup process is successful, store the > + * status in apic_id_wakemap to prevent re-wakeup > + * requests. > + */ > + physid_set(apicid, apic_id_wakemap); > + return 0; > + } > + > + /* If timed out (timeout == 0), return error */ > + return -EIO; > +} > + > #endif /*CONFIG_X86_LOCAL_APIC */ > > #ifdef CONFIG_X86_IO_APIC > @@ -1086,6 +1152,30 @@ static int __init acpi_parse_madt_lapic_entries(void) > } > return 0; > } > + > +static int __init acpi_parse_mp_wake(union acpi_subtable_headers *header, > + const unsigned long end) > +{ > + struct acpi_madt_multiproc_wakeup *mp_wake; > + > + if (acpi_mp_wake_mailbox) > + return -EINVAL; > + > + if (!IS_ENABLED(CONFIG_SMP)) > + return -ENODEV; > + > + mp_wake = (struct acpi_madt_multiproc_wakeup *)header; > + if (BAD_MADT_ENTRY(mp_wake, end)) > + return -EINVAL; > + > + acpi_table_print_madt_entry(&header->common); > + > + acpi_mp_wake_mailbox_paddr = mp_wake->base_address; > + > + acpi_wake_cpu_handler_update(acpi_wakeup_cpu); > + > + return 0; > +} > #endif /* CONFIG_X86_LOCAL_APIC */ > > #ifdef CONFIG_X86_IO_APIC > @@ -1284,6 +1374,12 @@ static void __init acpi_process_madt(void) > > smp_found_config = 1; > } > + > + /* > + * Parse MADT MP Wake entry. > + */ > + acpi_table_parse_madt(ACPI_MADT_TYPE_MULTIPROC_WAKEUP, > + acpi_parse_mp_wake, 1); > } > if (error == -EINVAL) { > /* > diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c > index 4f26700f314d..f1b90a4b89e8 100644 > --- a/arch/x86/kernel/apic/apic.c > +++ b/arch/x86/kernel/apic/apic.c > @@ -2554,6 +2554,14 @@ u32 x86_msi_msg_get_destid(struct msi_msg *msg, bool extid) > } > EXPORT_SYMBOL_GPL(x86_msi_msg_get_destid); > > +void __init acpi_wake_cpu_handler_update(wakeup_cpu_handler handler) > +{ > + struct apic **drv; > + > + for (drv = __apicdrivers; drv < __apicdrivers_end; drv++) > + (*drv)->wakeup_secondary_cpu = handler; > +} > + > /* > * Override the generic EOI implementation with an optimized version. > * Only called during early boot when only one CPU is active and with