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 Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 83DFBC433EF for ; Fri, 14 Jan 2022 03:13:39 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id 39407402C3; Fri, 14 Jan 2022 03:13:39 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id YPiX8GhaqLiC; Fri, 14 Jan 2022 03:13:38 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp2.osuosl.org (Postfix) with ESMTPS id C4E1940275; Fri, 14 Jan 2022 03:13:37 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 99EADC0030; Fri, 14 Jan 2022 03:13:37 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [IPv6:2605:bc80:3010::136]) by lists.linuxfoundation.org (Postfix) with ESMTP id E0CA1C001E for ; Fri, 14 Jan 2022 03:13:36 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id BB47A60AA9 for ; Fri, 14 Jan 2022 03:13:36 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp3.osuosl.org (amavisd-new); dkim=pass (2048-bit key) header.d=intel.com Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id TOkldFfwjZmh for ; Fri, 14 Jan 2022 03:13:36 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by smtp3.osuosl.org (Postfix) with ESMTPS id 2019460A89 for ; Fri, 14 Jan 2022 03:13:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1642130016; x=1673666016; h=cc:subject:to:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=Szmsi12k0LI7khEwP6fZbgXfWxt5yjoq0TShGWuPc+o=; b=RzGb35yihIrzCKnfbKbShf42UGHyg+2WwuphQ63cx4z2hcNUlivEzCA1 4OUkc9NhkoYYjIW70Bhak5sjF2bLbSF44dkzA0iohRpiIYBFozJOZbiTA EjXQKt7NcQz6E5CeE0172Mp9tUlV2L5O3+cc5i2hIJL4eezNlsVa6uZ3M +w5OkUZlEUEtP8k8aJoqRO+33cBYeaFjU1raGL+RyVgwZxWxGEDr2nLk0 SVKEx8ivM8FyaX1RAhlRkfcDJDwsJMO3HRGAgvvfXhkANhOB5+EXMdcgp slArw+Z2LWVghXFNL8UwUB4gMcr20eVToTrCGTZJK+PeaWG+6hbsycopm w==; X-IronPort-AV: E=McAfee;i="6200,9189,10226"; a="244128683" X-IronPort-AV: E=Sophos;i="5.88,287,1635231600"; d="scan'208";a="244128683" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jan 2022 19:13:35 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,287,1635231600"; d="scan'208";a="529971183" Received: from allen-box.sh.intel.com (HELO [10.239.159.118]) ([10.239.159.118]) by orsmga008.jf.intel.com with ESMTP; 13 Jan 2022 19:13:33 -0800 Subject: Re: [PATCH] iommu/vt-d: Fix PCI bus rescan device hot add To: Jacob Pan References: <1642080198-10971-1-git-send-email-jacob.jun.pan@linux.intel.com> <20220113191122.53bc6ac0@jacob-builder> From: Lu Baolu Message-ID: <1b8d3145-c404-e952-e61e-5cdc2f6a92a6@linux.intel.com> Date: Fri, 14 Jan 2022 11:12:45 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20220113191122.53bc6ac0@jacob-builder> Content-Language: en-US Cc: Raj Ashok , "Kumar, Sanjay K" , LKML , iommu@lists.linux-foundation.org, Jacob Pan 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-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 1/14/22 11:11 AM, Jacob Pan wrote: > On Fri, 14 Jan 2022 08:58:53 +0800, Lu Baolu > wrote: > >> Hi Jacob, >> >> On 1/13/22 9:23 PM, Jacob Pan wrote: >>> During PCI bus rescan, adding new devices involve two notifiers. >>> 1. dmar_pci_bus_notifier() >>> 2. iommu_bus_notifier() >>> The current code sets #1 as low priority (INT_MIN) which resulted in #2 >>> being invoked first. The result is that struct device pointer cannot be >>> found in DRHD search for the new device's DMAR/IOMMU. Subsequently, the >>> device is put under the "catch-all" IOMMU instead of the correct one. >>> >>> This could cause system hang when device TLB invalidation is sent to the >>> wrong IOMMU. Invalidation timeout error or hard lockup can be observed. >>> >>> This patch fixes the issue by setting a higher priority for >>> dmar_pci_bus_notifier. DRHD search for a new device will find the >>> correct IOMMU. >>> >>> Fixes: 59ce0515cdaf ("iommu/vt-d: Update DRHD/RMRR/ATSR device scope") >>> Reported-by: Zhang, Bernice >>> Signed-off-by: Jacob Pan >>> --- >>> drivers/iommu/intel/dmar.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c >>> index 915bff76fe96..5d07e5b89c2e 100644 >>> --- a/drivers/iommu/intel/dmar.c >>> +++ b/drivers/iommu/intel/dmar.c >>> @@ -385,7 +385,7 @@ static int dmar_pci_bus_notifier(struct >>> notifier_block *nb, >>> static struct notifier_block dmar_pci_bus_nb = { >>> .notifier_call = dmar_pci_bus_notifier, >>> - .priority = INT_MIN, >>> + .priority = INT_MAX, >>> }; >>> >>> static struct dmar_drhd_unit * >>> >> Nice catch! dmar_pci_bus_add_dev() should take place*before* >> iommu_probe_device(). This change enforces this with a higher notifier >> priority for dmar callback. >> >> Comparably, dmar_pci_bus_del_dev() should take place*after* >> iommu_release_device(). Perhaps we can use two notifiers, one for >> ADD_DEVICE (with .priority=INT_MAX) and the other for REMOVE_DEVICE >> (with .priority=INT_MIN)? >> > Since device_to_iommu() lookup in intel_iommu_release_device() only > checks if device is under "an" IOMMU, not "the" IOMMU. Then the remove path > order is not needed, right? > > I know this is not robust, but having so many notifiers with implicit > priority is not clean either. > > Perhaps, we should have explicit priority defined around iommu_bus > notifier? i.e. > > @@ -1841,6 +1841,7 @@ static int iommu_bus_init(struct bus_type *bus, const > struct iommu_ops *ops) return -ENOMEM; > nb->notifier_call = iommu_bus_notifier; > > + nb->priority = IOMMU_BUS_NOTIFY_PRIORITY; > > > static struct notifier_block dmar_pci_bus_add_nb = { > .notifier_call = dmar_pci_bus_notifier, > - .priority = INT_MIN, > + .priority = IOMMU_BUS_NOTIFY_PRIORITY + 1, > }; > > static struct notifier_block dmar_pci_bus_remove_nb = { > .notifier_call = dmar_pci_bus_notifier, > - .priority = INT_MIN, > + .priority = IOMMU_BUS_NOTIFY_PRIORITY - 1, > }; IOMMU_BUS_NOTIFY_PRIORITY by default is 0. So you can simply use 1 and -1? Adding a comment around it will be helpful. Best regards, baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu