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=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 CA067C433DB for ; Sat, 20 Mar 2021 02:19:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B66F6194B for ; Sat, 20 Mar 2021 02:19:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229648AbhCTCS4 (ORCPT ); Fri, 19 Mar 2021 22:18:56 -0400 Received: from mga11.intel.com ([192.55.52.93]:23351 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229870AbhCTCSj (ORCPT ); Fri, 19 Mar 2021 22:18:39 -0400 IronPort-SDR: vQmIFFW8aAnnNHDVDsCwDXPkEISVk5YHLjEsENBDhpFyKqkyd3D7cYMmRLddJIlpuaGSfMhXSN bbVM7tLOCcgw== X-IronPort-AV: E=McAfee;i="6000,8403,9928"; a="186657686" X-IronPort-AV: E=Sophos;i="5.81,263,1610438400"; d="scan'208";a="186657686" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Mar 2021 19:18:38 -0700 IronPort-SDR: ifCZBgEbNVm4RtJUYXhspW+lf4lAWdTcukLek85azk0D9uY8kRdm8kqljVo6iT21BK1dRHFuzw GPjPR5c1+GDg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.81,263,1610438400"; d="scan'208";a="512681377" Received: from allen-box.sh.intel.com ([10.239.159.128]) by fmsmga001.fm.intel.com with ESMTP; 19 Mar 2021 19:18:37 -0700 From: Lu Baolu To: Joerg Roedel , Will Deacon Cc: Dave Jiang , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Lu Baolu Subject: [PATCH v2 1/1] iommu/vt-d: Fix lockdep splat in intel_pasid_get_entry() Date: Sat, 20 Mar 2021 10:09:16 +0800 Message-Id: <20210320020916.640115-1-baolu.lu@linux.intel.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The pasid_lock is used to synchronize different threads from modifying a same pasid directory entry at the same time. It causes below lockdep splat. [ 83.296538] ======================================================== [ 83.296538] WARNING: possible irq lock inversion dependency detected [ 83.296539] 5.12.0-rc3+ #25 Tainted: G W [ 83.296539] -------------------------------------------------------- [ 83.296540] bash/780 just changed the state of lock: [ 83.296540] ffffffff82b29c98 (device_domain_lock){..-.}-{2:2}, at: iommu_flush_dev_iotlb.part.0+0x32/0x110 [ 83.296547] but this lock took another, SOFTIRQ-unsafe lock in the past: [ 83.296547] (pasid_lock){+.+.}-{2:2} [ 83.296548] and interrupts could create inverse lock ordering between them. [ 83.296549] other info that might help us debug this: [ 83.296549] Chain exists of: device_domain_lock --> &iommu->lock --> pasid_lock [ 83.296551] Possible interrupt unsafe locking scenario: [ 83.296551] CPU0 CPU1 [ 83.296552] ---- ---- [ 83.296552] lock(pasid_lock); [ 83.296553] local_irq_disable(); [ 83.296553] lock(device_domain_lock); [ 83.296554] lock(&iommu->lock); [ 83.296554] [ 83.296554] lock(device_domain_lock); [ 83.296555] *** DEADLOCK *** Fix it by replacing the pasid_lock with an atomic exchange operation. Reported-and-tested-by: Dave Jiang Signed-off-by: Lu Baolu --- drivers/iommu/intel/pasid.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) Log: v1->v2: - v1: https://lore.kernel.org/linux-iommu/20210317005834.173503-1-baolu.lu@linux.intel.com/ - Use retry to make code neat; - Add a comment about no clear case, hence no race. diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c index 7a73385edcc0..f2c747e62c6a 100644 --- a/drivers/iommu/intel/pasid.c +++ b/drivers/iommu/intel/pasid.c @@ -24,7 +24,6 @@ /* * Intel IOMMU system wide PASID name space: */ -static DEFINE_SPINLOCK(pasid_lock); u32 intel_pasid_max_id = PASID_MAX; int vcmd_alloc_pasid(struct intel_iommu *iommu, u32 *pasid) @@ -259,19 +258,25 @@ struct pasid_entry *intel_pasid_get_entry(struct device *dev, u32 pasid) dir_index = pasid >> PASID_PDE_SHIFT; index = pasid & PASID_PTE_MASK; - spin_lock(&pasid_lock); +retry: entries = get_pasid_table_from_pde(&dir[dir_index]); if (!entries) { entries = alloc_pgtable_page(info->iommu->node); - if (!entries) { - spin_unlock(&pasid_lock); + if (!entries) return NULL; - } - WRITE_ONCE(dir[dir_index].val, - (u64)virt_to_phys(entries) | PASID_PTE_PRESENT); + /* + * The pasid directory table entry won't be freed after + * allocation. No worry about the race with free and + * clear. However, this entry might be populated by others + * while we are preparing it. Use theirs with a retry. + */ + if (cmpxchg64(&dir[dir_index].val, 0ULL, + (u64)virt_to_phys(entries) | PASID_PTE_PRESENT)) { + free_pgtable_page(entries); + goto retry; + } } - spin_unlock(&pasid_lock); return &entries[index]; } -- 2.25.1