From nobody Wed Dec 17 09:44:26 2025 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9409AC001DF for ; Fri, 20 Oct 2023 15:13:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377646AbjJTPNV (ORCPT ); Fri, 20 Oct 2023 11:13:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34598 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1377650AbjJTPNM (ORCPT ); Fri, 20 Oct 2023 11:13:12 -0400 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E8D31D7B for ; Fri, 20 Oct 2023 08:13:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1697814784; x=1729350784; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=OLVOdxFnd1PuTcNaoWBVdKJvyZnZKOsxD6fGknmiUv0=; b=eBfDKdI84lEnBrHqq91rR3djTOLizxToQglynzeV9IX/wor4SOLT8lea HhXNSf2MLox4td8IY6Gl8BnEuG3rIUKWCEnISKXU8QwQmy65WAs64LDxP xv82WTHctLP+0q8t3mYcugM5EyLFCG3mrmiDz1L7tUXjfXuvFJPDQT4mC DCoIpQDoq/VJJfPu4U6yKvUXzwNP+cf0bWQlcvMjJkW7kEYOqXFxu9cuo cTK8PcR8dQgX+Hiho1QJVBaz9LpMChiOyArUb/RLCmqrBol/etMiWOI4f smRdvM5bsKc4pVu0qbqQe+nVx9hwLiV9fYUzDn50XKi1361k01O6Qqts6 w==; X-IronPort-AV: E=McAfee;i="6600,9927,10869"; a="376893672" X-IronPort-AV: E=Sophos;i="6.03,239,1694761200"; d="scan'208";a="376893672" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2023 08:13:01 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10869"; a="761080288" X-IronPort-AV: E=Sophos;i="6.03,239,1694761200"; d="scan'208";a="761080288" Received: from dgutows1-mobl.ger.corp.intel.com (HELO box.shutemov.name) ([10.249.39.237]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2023 08:12:56 -0700 Received: by box.shutemov.name (Postfix, from userid 1000) id 5C61110A29D; Fri, 20 Oct 2023 18:12:45 +0300 (+03) From: "Kirill A. Shutemov" To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org Cc: "Rafael J. Wysocki" , Peter Zijlstra , Adrian Hunter , Kuppuswamy Sathyanarayanan , Elena Reshetova , Jun Nakajima , Rick Edgecombe , Tom Lendacky , "Kalra, Ashish" , Sean Christopherson , "Huang, Kai" , Baoquan He , kexec@lists.infradead.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: [PATCHv2 11/13] x86/acpi: Do not attempt to bring up secondary CPUs in kexec case Date: Fri, 20 Oct 2023 18:12:40 +0300 Message-ID: <20231020151242.1814-12-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20231020151242.1814-1-kirill.shutemov@linux.intel.com> References: <20231020151242.1814-1-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" ACPI MADT doesn't allow to offline CPU after it got woke up. It limits kexec: the second kernel won't be able to use more than one CPU. Now acpi_mp_wake_mailbox_paddr already has the mailbox address. The acpi_wakeup_cpu() will use it to bring up secondary cpus. Zero out mailbox address in the ACPI MADT wakeup structure to indicate that the mailbox is not usable. This prevents the kexec()-ed kernel from reading a vaild mailbox, which in turn makes the kexec()-ed kernel only be able to use the boot CPU. This is Linux-specific protocol and not reflected in ACPI spec. Booting the second kernel with signle CPU is enough to cover the most common case for kexec -- kdump. Signed-off-by: Kirill A. Shutemov Reviewed-by: Kai Huang --- arch/x86/kernel/acpi/madt_wakeup.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt= _wakeup.c index 4bc1d5106afd..9bbe829737e7 100644 --- a/arch/x86/kernel/acpi/madt_wakeup.c +++ b/arch/x86/kernel/acpi/madt_wakeup.c @@ -13,6 +13,11 @@ static struct acpi_madt_multiproc_wakeup_mailbox *acpi_m= p_wake_mailbox; =20 static int acpi_wakeup_cpu(int apicid, unsigned long start_ip) { + if (!acpi_mp_wake_mailbox_paddr) { + pr_warn_once("No MADT mailbox: cannot bringup secondary CPUs. Booting wi= th kexec?\n"); + return -EOPNOTSUPP; + } + /* * Remap mailbox memory only for the first call to acpi_wakeup_cpu(). * @@ -78,6 +83,23 @@ int __init acpi_parse_mp_wake(union acpi_subtable_header= s *header, =20 cpu_hotplug_disable_offlining(); =20 + /* + * ACPI MADT doesn't allow to offline CPU after it got woke up. + * It limits kexec: the second kernel won't be able to use more than + * one CPU. + * + * Now acpi_mp_wake_mailbox_paddr already has the mailbox address. + * The acpi_wakeup_cpu() will use it to bring up secondary cpus. + * + * Zero out mailbox address in the ACPI MADT wakeup structure to + * indicate that the mailbox is not usable. This prevents the + * kexec()-ed kernel from reading a vaild mailbox, which in turn + * makes the kexec()-ed kernel only be able to use the boot CPU. + * + * This is Linux-specific protocol and not reflected in ACPI spec. + */ + mp_wake->base_address =3D 0; + apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu); =20 return 0; --=20 2.41.0