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=-13.8 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 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 52783C433E0 for ; Thu, 18 Mar 2021 10:21:20 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EA3C964E99 for ; Thu, 18 Mar 2021 10:21:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA3C964E99 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=8bytes.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 90EC383EDF; Thu, 18 Mar 2021 10:21:19 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id imEgFwdDAcep; Thu, 18 Mar 2021 10:21:18 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp1.osuosl.org (Postfix) with ESMTP id 59A7183CE6; Thu, 18 Mar 2021 10:21:18 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 2A831C000B; Thu, 18 Mar 2021 10:21:18 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [IPv6:2605:bc80:3010::138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 2B861C0001 for ; Thu, 18 Mar 2021 10:21:17 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 121E483E9F for ; Thu, 18 Mar 2021 10:21:17 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id jYmMGKULEy7i for ; Thu, 18 Mar 2021 10:21:16 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0 Received: from theia.8bytes.org (8bytes.org [IPv6:2a01:238:4383:600:38bc:a715:4b6d:a889]) by smtp1.osuosl.org (Postfix) with ESMTPS id 1817F83CE6 for ; Thu, 18 Mar 2021 10:21:16 +0000 (UTC) Received: by theia.8bytes.org (Postfix, from userid 1000) id 084412D8; Thu, 18 Mar 2021 11:21:13 +0100 (CET) Date: Thu, 18 Mar 2021 11:21:12 +0100 From: Joerg Roedel To: Lu Baolu Subject: Re: [PATCH 1/1] iommu/vt-d: Fix lockdep splat in intel_pasid_get_entry() Message-ID: References: <20210317005834.173503-1-baolu.lu@linux.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210317005834.173503-1-baolu.lu@linux.intel.com> Cc: Dave Jiang , iommu@lists.linux-foundation.org, Will Deacon , linux-kernel@vger.kernel.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Wed, Mar 17, 2021 at 08:58:34AM +0800, Lu Baolu wrote: > 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]); This is racy, someone could have already cleared the pasid-entry again. What you need to do here is to retry the whole path by adding a goto to before the first get_pasid_table_from_pde() call. Btw, what makes sure that the pasid_entry does not go away when it is returned here? Regards, Joerg _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu