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,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 CE360C433DB for ; Wed, 17 Mar 2021 01:08:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 95B9C64F21 for ; Wed, 17 Mar 2021 01:08:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230499AbhCQBIa (ORCPT ); Tue, 16 Mar 2021 21:08:30 -0400 Received: from mga07.intel.com ([134.134.136.100]:5477 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233901AbhCQBHz (ORCPT ); Tue, 16 Mar 2021 21:07:55 -0400 IronPort-SDR: FWOGLQTNIub8tRW2jM8Et/YzGFVXEzPAR01HzH5aWVVreV+zyW/bu+OqEoLaVpWvdzvhrvVyOP Nx7sKidq/Z5g== X-IronPort-AV: E=McAfee;i="6000,8403,9925"; a="253377355" X-IronPort-AV: E=Sophos;i="5.81,254,1610438400"; d="scan'208";a="253377355" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Mar 2021 18:07:55 -0700 IronPort-SDR: 5ESqZJpr09Vf0XxYYlkBPIf+V6tM3LPH9pyOCKYFkYtt+p3g3W2yafDGSwqh3Kvw1IFeEftrS9 bsXrt30ki69Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.81,254,1610438400"; d="scan'208";a="511560007" Received: from allen-box.sh.intel.com ([10.239.159.128]) by fmsmga001.fm.intel.com with ESMTP; 16 Mar 2021 18:07:53 -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 1/1] iommu/vt-d: Fix lockdep splat in intel_pasid_get_entry() Date: Wed, 17 Mar 2021 08:58:34 +0800 Message-Id: <20210317005834.173503-1-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 | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c index 9fb3d3e80408..1ddcb8295f72 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 +258,18 @@ 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); 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); + if (cmpxchg64(&dir[dir_index].val, 0ULL, + (u64)virt_to_phys(entries) | PASID_PTE_PRESENT)) { + free_pgtable_page(entries); + entries = get_pasid_table_from_pde(&dir[dir_index]); + } } - spin_unlock(&pasid_lock); return &entries[index]; } -- 2.25.1