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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 17A0DC3A59F for ; Mon, 26 Aug 2019 10:16:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ED96E21872 for ; Mon, 26 Aug 2019 10:15:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730820AbfHZKPy (ORCPT ); Mon, 26 Aug 2019 06:15:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38484 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730790AbfHZKPu (ORCPT ); Mon, 26 Aug 2019 06:15:50 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 88ACA883C2; Mon, 26 Aug 2019 10:15:50 +0000 (UTC) Received: from gigantic.usersys.redhat.com (helium.bos.redhat.com [10.18.17.132]) by smtp.corp.redhat.com (Postfix) with ESMTP id EAFED60920; Mon, 26 Aug 2019 10:15:49 +0000 (UTC) From: Bandan Das To: Thomas Gleixner , Ingo Molnar , Borislav Petkov Cc: x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/2] x86/apic: Do not initialize LDR and DFR for bigsmp Date: Mon, 26 Aug 2019 06:15:12 -0400 Message-Id: <20190826101513.5080-2-bsd@redhat.com> In-Reply-To: <20190826101513.5080-1-bsd@redhat.com> References: <20190826101513.5080-1-bsd@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Mon, 26 Aug 2019 10:15:50 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Legacy apic init uses bigsmp for > 8 smp systems. In these cases, PhysFlat will invariably be used and there is no point in initializing apic LDR and DFR. Furthermore, calculate_ldr() helper function was incorrectly setting multiple bits in the LDR. This was discovered with a 32 bit KVM guest loading the kdump kernel. Owing to the multiple bits being incorrectly set in the LDR, KVM hit a buggy "if" condition in the kvm lapic implementation that creates the logical destination map for vcpus - it ends up overwriting and existing valid entry and as a result, apic calibration hangs in the guest during kdump initialization. Note that this change isn't intended to workaround the kvm lapic bug; bigsmp should correctly stay away from initializing LDR. Suggested-by: Thomas Gleixner Signed-off-by: Bandan Das --- arch/x86/kernel/apic/bigsmp_32.c | 24 ++---------------------- 1 file changed, 2 insertions(+), 22 deletions(-) diff --git a/arch/x86/kernel/apic/bigsmp_32.c b/arch/x86/kernel/apic/bigsmp_32.c index afee386ff711..caedd8d60d36 100644 --- a/arch/x86/kernel/apic/bigsmp_32.c +++ b/arch/x86/kernel/apic/bigsmp_32.c @@ -38,32 +38,12 @@ static int bigsmp_early_logical_apicid(int cpu) return early_per_cpu(x86_cpu_to_apicid, cpu); } -static inline unsigned long calculate_ldr(int cpu) -{ - unsigned long val, id; - - val = apic_read(APIC_LDR) & ~APIC_LDR_MASK; - id = per_cpu(x86_bios_cpu_apicid, cpu); - val |= SET_APIC_LOGICAL_ID(id); - - return val; -} - /* - * Set up the logical destination ID. - * - * Intel recommends to set DFR, LDR and TPR before enabling - * an APIC. See e.g. "AP-388 82489DX User's Manual" (Intel - * document number 292116). So here it goes... + * bigsmp enables physical destination mode + * and doesn't use LDR and DFR */ static void bigsmp_init_apic_ldr(void) { - unsigned long val; - int cpu = smp_processor_id(); - - apic_write(APIC_DFR, APIC_DFR_FLAT); - val = calculate_ldr(cpu); - apic_write(APIC_LDR, val); } static void bigsmp_setup_apic_routing(void) -- 2.20.1