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=-19.0 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, USER_AGENT_GIT autolearn=unavailable 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 03245C46461 for ; Mon, 15 Mar 2021 14:01:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DEF5E64F2E for ; Mon, 15 Mar 2021 14:01:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233430AbhCOOBk (ORCPT ); Mon, 15 Mar 2021 10:01:40 -0400 Received: from mail.kernel.org ([198.145.29.99]:33544 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230526AbhCON4p (ORCPT ); Mon, 15 Mar 2021 09:56:45 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A080464F04; Mon, 15 Mar 2021 13:56:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1615816594; bh=lQqZ31p/1FjojljzydhEX/AOh6vMwibdy62aoftNbNg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hc/cL7NIqSMeOf+bpVjXuEwGiLITqZH065SfZX0nrYZofQGQI2ddofkyNbD/8wqJZ Zcdmft1IlF1HqpUKJNFFIb6RSjAkkx4qt3cJiwDYSbFFiKUyiv5UPf05WgyazwmK6c rWzJ8TLNeRCvuUgRbtDEfoHgiha5JKFxMhJf8NGc= From: gregkh@linuxfoundation.org To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Greg Kurz , Laurent Vivier , =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= , Michael Ellerman Subject: [PATCH 5.10 003/290] powerpc/pseries: Dont enforce MSI affinity with kdump Date: Mon, 15 Mar 2021 14:51:36 +0100 Message-Id: <20210315135542.049540354@linuxfoundation.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210315135541.921894249@linuxfoundation.org> References: <20210315135541.921894249@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Greg Kroah-Hartman From: Greg Kurz commit f9619d5e5174867536b7e558683bc4408eab833f upstream. Depending on the number of online CPUs in the original kernel, it is likely for CPU #0 to be offline in a kdump kernel. The associated IRQs in the affinity mappings provided by irq_create_affinity_masks() are thus not started by irq_startup(), as per-design with managed IRQs. This can be a problem with multi-queue block devices driven by blk-mq : such a non-started IRQ is very likely paired with the single queue enforced by blk-mq during kdump (see blk_mq_alloc_tag_set()). This causes the device to remain silent and likely hangs the guest at some point. This is a regression caused by commit 9ea69a55b3b9 ("powerpc/pseries: Pass MSI affinity to irq_create_mapping()"). Note that this only happens with the XIVE interrupt controller because XICS has a workaround to bypass affinity, which is activated during kdump with the "noirqdistrib" kernel parameter. The issue comes from a combination of factors: - discrepancy between the number of queues detected by the multi-queue block driver, that was used to create the MSI vectors, and the single queue mode enforced later on by blk-mq because of kdump (i.e. keeping all queues fixes the issue) - CPU#0 offline (i.e. kdump always succeed with CPU#0) Given that I couldn't reproduce on x86, which seems to always have CPU#0 online even during kdump, I'm not sure where this should be fixed. Hence going for another approach : fine-grained affinity is for performance and we don't really care about that during kdump. Simply revert to the previous working behavior of ignoring affinity masks in this case only. Fixes: 9ea69a55b3b9 ("powerpc/pseries: Pass MSI affinity to irq_create_mapping()") Cc: stable@vger.kernel.org # v5.10+ Signed-off-by: Greg Kurz Reviewed-by: Laurent Vivier Reviewed-by: Cédric Le Goater Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210215094506.1196119-1-groug@kaod.org Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/platforms/pseries/msi.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) --- a/arch/powerpc/platforms/pseries/msi.c +++ b/arch/powerpc/platforms/pseries/msi.c @@ -4,6 +4,7 @@ * Copyright 2006-2007 Michael Ellerman, IBM Corp. */ +#include #include #include #include @@ -458,8 +459,28 @@ again: return hwirq; } - virq = irq_create_mapping_affinity(NULL, hwirq, - entry->affinity); + /* + * Depending on the number of online CPUs in the original + * kernel, it is likely for CPU #0 to be offline in a kdump + * kernel. The associated IRQs in the affinity mappings + * provided by irq_create_affinity_masks() are thus not + * started by irq_startup(), as per-design for managed IRQs. + * This can be a problem with multi-queue block devices driven + * by blk-mq : such a non-started IRQ is very likely paired + * with the single queue enforced by blk-mq during kdump (see + * blk_mq_alloc_tag_set()). This causes the device to remain + * silent and likely hangs the guest at some point. + * + * We don't really care for fine-grained affinity when doing + * kdump actually : simply ignore the pre-computed affinity + * masks in this case and let the default mask with all CPUs + * be used when creating the IRQ mappings. + */ + if (is_kdump_kernel()) + virq = irq_create_mapping(NULL, hwirq); + else + virq = irq_create_mapping_affinity(NULL, hwirq, + entry->affinity); if (!virq) { pr_debug("rtas_msi: Failed mapping hwirq %d\n", hwirq);