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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5888DC433EF for ; Fri, 14 Jan 2022 03:06:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238998AbiANDGr (ORCPT ); Thu, 13 Jan 2022 22:06:47 -0500 Received: from mga03.intel.com ([134.134.136.65]:8463 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236150AbiANDGq (ORCPT ); Thu, 13 Jan 2022 22:06:46 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1642129606; x=1673665606; h=date:from:to:cc:subject:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=6aJ6oA9KZ9H5+yC8/t8/dEXbjQd4pxgYYBjq4dVBGz4=; b=ZKW18vlzOghny866oBDb3iI/KJXPOI0PYBtV3lFWh4xDi85kn/HvHq1x f91O6wGqirQyeBC0IQi3MFKmWbv/u9GU/BU6QUCbLNHv9qYgslhRIGn9g v/PexDd8tamZyjRYyXmDBBQmnBSZM3UO0lQycWY7KXHxEpVDyMRrz2LKZ g7iRz6sgPRvxDyE+3EXqOuIca8X7E6eXCQ6hYh1KBu2aUz97Q3Cf7Jld4 S3MSQV/+30s1cy//UsEdnRGN/UnDPnR6yAiTFsZFRHC3/TIkqxvxzJN9v QIfFUyqvJdnlYI26LHS/pYyxGHQwaYG1oW5E/WRB4SNacU2Jyctrk9uVX g==; X-IronPort-AV: E=McAfee;i="6200,9189,10226"; a="244128025" X-IronPort-AV: E=Sophos;i="5.88,287,1635231600"; d="scan'208";a="244128025" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jan 2022 19:06:45 -0800 X-IronPort-AV: E=Sophos;i="5.88,287,1635231600"; d="scan'208";a="670725195" Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jan 2022 19:06:45 -0800 Date: Thu, 13 Jan 2022 19:11:22 -0800 From: Jacob Pan To: Lu Baolu Cc: iommu@lists.linux-foundation.org, LKML , Joerg Roedel , Jacob Pan , Raj Ashok , "Kumar, Sanjay K" , jacob.jun.pan@linux.intel.com Subject: Re: [PATCH] iommu/vt-d: Fix PCI bus rescan device hot add Message-ID: <20220113191122.53bc6ac0@jacob-builder> In-Reply-To: References: <1642080198-10971-1-git-send-email-jacob.jun.pan@linux.intel.com> Organization: OTC X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi BaoLu, 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, }; > Best regards, > baolu Thanks, Jacob