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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 8F5DDC43219 for ; Tue, 26 Jan 2021 17:46:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6AAD922210 for ; Tue, 26 Jan 2021 17:46:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393341AbhAZRqZ (ORCPT ); Tue, 26 Jan 2021 12:46:25 -0500 Received: from mga03.intel.com ([134.134.136.65]:7333 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389685AbhAZIRn (ORCPT ); Tue, 26 Jan 2021 03:17:43 -0500 IronPort-SDR: aXEIvNg2Od9NFNvG3ii+ffGkRK+ut/kgJhP9ZwM1eg3wpzSzLFv9c55MkfFG6wMyQQt2QElVXN HarnJea+ltOw== X-IronPort-AV: E=McAfee;i="6000,8403,9875"; a="179946985" X-IronPort-AV: E=Sophos;i="5.79,375,1602572400"; d="scan'208";a="179946985" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jan 2021 00:15:52 -0800 IronPort-SDR: RyXTL8a39rMcJII30OSQ7JLgYTMXws0K6NW/SnkAdeFm/Eq4q0GvY6UvHmA0IGL8IoQkA7xETY pglZrRdtAJSA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.79,375,1602572400"; d="scan'208";a="577725450" Received: from allen-box.sh.intel.com ([10.239.159.128]) by fmsmga005.fm.intel.com with ESMTP; 26 Jan 2021 00:15:50 -0800 From: Lu Baolu To: Joerg Roedel , Will Deacon Cc: Ashok Raj , Jacob Pan , Kevin Tian , Liu Yi L , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Lu Baolu Subject: [PATCH v2 1/2] iommu/vt-d: Clear PRQ overflow only when PRQ is empty Date: Tue, 26 Jan 2021 16:07:29 +0800 Message-Id: <20210126080730.2232859-2-baolu.lu@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210126080730.2232859-1-baolu.lu@linux.intel.com> References: <20210126080730.2232859-1-baolu.lu@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It is incorrect to always clear PRO when it's set w/o first checking whether the overflow condition has been cleared. Current code assumes that if an overflow condition occurs it must have been cleared by earlier loop. However since the code runs in a threaded context, the overflow condition could occur even after setting the head to the tail under some extreme condition. To be sane, we should read both head/tail again when seeing a pending PRO and only clear PRO after all pending PRs have been handled. Suggested-by: Kevin Tian Link: https://lore.kernel.org/linux-iommu/MWHPR11MB18862D2EA5BD432BF22D99A48CA09@MWHPR11MB1886.namprd11.prod.outlook.com/ Signed-off-by: Lu Baolu --- drivers/iommu/intel/svm.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c index 033b25886e57..d7c98c5fa4e7 100644 --- a/drivers/iommu/intel/svm.c +++ b/drivers/iommu/intel/svm.c @@ -1042,8 +1042,17 @@ static irqreturn_t prq_event_thread(int irq, void *d) * Clear the page request overflow bit and wake up all threads that * are waiting for the completion of this handling. */ - if (readl(iommu->reg + DMAR_PRS_REG) & DMA_PRS_PRO) - writel(DMA_PRS_PRO, iommu->reg + DMAR_PRS_REG); + if (readl(iommu->reg + DMAR_PRS_REG) & DMA_PRS_PRO) { + pr_info_ratelimited("IOMMU: %s: PRQ overflow detected\n", + iommu->name); + head = dmar_readq(iommu->reg + DMAR_PQH_REG) & PRQ_RING_MASK; + tail = dmar_readq(iommu->reg + DMAR_PQT_REG) & PRQ_RING_MASK; + if (head == tail) { + writel(DMA_PRS_PRO, iommu->reg + DMAR_PRS_REG); + pr_info_ratelimited("IOMMU: %s: PRQ overflow cleared", + iommu->name); + } + } if (!completion_done(&iommu->prq_complete)) complete(&iommu->prq_complete); -- 2.25.1